FSJ Frame Strength for a Diesel Swap

[The PIG Smith]

The recent posting created by Songman about the purchase of a 1990 Dodge Cummins 6BT as a donor for a FSJ Diesel project has prompted me to revisit this topic of Frame strength.
http://www.ifsja.org/forums/vb/showthread.php?t=121301

There is a debate (I would like to say a it's a HUGE debate, but I am sure there would be debate over the size of the debate) about FSJ Frames

Some say the FSJ frames are not strong.
They say the frame is not deep enough and not boxed enough and the material is not thick enough and is soft like butter to use for a Cummins 6BT.

Other say these frames are as strong as any other frame of the same era.

I would like discuss this more and other than just opinions (which are great for a discussion), I would love some more factual evidence.

I've dreamed of a Diesel FSJ for a long time.
Short of struggling to keep a roof over my head, I have not been able to move beyond the planning stage.

I've desired a Cummins 6BT, but the simplicity of the GM 6.2 Diesel swap have caused me to change my plans.
However, the source of this 1st gen Cummins 6BT is being to grow.
A person can find them in others places, like in School Buses and med duty trucks.

But, before anyone can address the issues related to the a Cummins 6BT, a person needs to have a good foundation, a good frame.

One factor is how would one use a 6BT powered FSJ.
A 6BT powered Wagoneer may lead a different life than a J20 tow rig.

Allow me to share my plans (fools fantasy) for a 6BT powered FSJ.
I would like a recovery rig, long range tow rig, dually rear axle, on board air (easy bolt on for a 6BT) and my flat bed would hold a 5th wheel hitch.

What I do with such a rig?
I want to be able to leave NE Indiana and head to the Southwest to collect those toys, like a 70 Nova, 67 Mercury Cougar, 71-74 Javelin, Jeep Forward Control, Fox Body Mustang (for Nathan) or a whole host of other interests that I have.

[1983 j10]

the easiest way to do that would probly be to find a dodge and put the fsj body on it. and since your doing a flat bed it would be pretty easy.

[Mikel]

I am partial to M715 frames. They are a bit stronger, boxed to a larger extent, have reinforcements that civilian frames don't have and have a built-in suspension lift that makes engine fitment a lot easier.

[76FSChief]

Glad to hear that I am not the only guy that has dreamed about a diesel Jeep. I am in the middle of the swap as we talk - engine, transmission and transfer case are all mounted up.

Originally I wanted to go with the original frame but people told me that I wouldnt be able to. Then I started thinking about doing the Dodge frame but after talking to a dealer out in Ontario I decided to go with my original idea. He said all that is necessary is a little reinforcement of the frame and your good to go - they have done the swap a few times with no customer complaints.

Anyways I am going to get a thread going for the build, and if I can help you out in anyway just let me know.

[Songman]

Even though the particular truck I was interested in got sold, I am still interested in this swap so will watch with interest. I'm on the lookout for an affordable donor.

[vintagetrks]

Would you have to beef up the frame for a GM 6.2 swap. I would think the only reason a fellow would have to beef the frame up for the cummins is the higher torque. Because it would seem to me that the GM 6.2 would be a heavier engine than the 6bt but I'd bet the 6.2 does'nt produce near the torque of the 6bt. Just a thought.

[HOOT]

HOOT says:
Buy a truck you like and morph it into a FSJ knock off. I finally got fustrated when after years of work my J20 got destroyed on Its maiden trip after being rebuilt. Diesel was to come later after the Honcho was back on the street. No longer with a tow rig I was at square one not to mention the money loss. So after long debate I went outside the Jeep world for a truck,something I have never done in my life and I was 45 years old. Picked up a somewhat well taken care of '95 F350 and did a refresher on it. The power and drive is unbelieveable not to mention the safety as well. Yes I could of made my J20 back to this type of tow ability and stable road manners but I didn't see that happening with the struggles the past couple of years.

My neighbors roll their eyes as the see me wire tying a razor or muscle grill to the Ford sizing it up. It can be done, like dropping in a different drive line its all just a matter of fabbing. Only in this case I'm keeping factory driveline and changing its skin as much as possible.

I have a utility bed I bought for the Jeep. It's a Reading and as anyone knows it looks nothing like a Jeep even when its on a Jeep. So I found a use for my factory fiber glass rear flares no one wanted to buy. I also have a set of rear J truck tail lights that will be grafted in place of the round Reading lights. My J truck rear bumper will most likely be installed as well, although there is a sweet after market step bumper I want also. Since I prefer the looks of a brow truck I'll most likely put a Lund visor on it for the unibrow bliss.
It's a factory crew cab so now I'll have my sleeper unit as well that I wanted. All I have to haul is me and Annie, and she prefers shotgun. I picked up a killer topper for it from a TX member on here(Thanks Jason).
This thing can pull the house of its foundation and still get me to the Dairy Queen for a sundae. Capable of hauling gooseneck or bumper pull and able to do it cross country like a Sunday drive.
I have about $3000 more into this as I had into my J20 and it was still sporting the 360 motor, dana 44/60 SRW 3:73 gears and regular cab with 8' bed.
I now have 7.3 (brace yourself Derek) Turbo !! diesel, with overdrive, crew cab, Sterling 10.25 dually,4:10 gears, with a locker and dual fuel tanks.
Soon it will have the utility bed and other Jeep stuff as I get time to work it over. It may never be a Jeep but it has an older Ford style that I like, and most of all so far very dependable after being worked fairly hard the last year or so. 20,000 miles on it in less than a year and it sits for week or more at a time as I have a different daily driver car that gets all non hauling type driving.

So turn your J trucks into diesels if you want but its my love for getting back behind the wheel of my Honcho and wanting to take it back to its homeland in the Southwest that forces me to change tow rigs, even if it means being towed by a Ford to get there.
Now if they only had a F350 site as nice as this one is.....:(

[The PIG Smith]

Would you have to beef up the frame for a GM 6.2 swap. I would think the only reason a fellow would have to beef the frame up for the cummins is the higher torque. Because it would seem to me that the GM 6.2 would be a heavier engine than the 6bt but I'd bet the 6.2 does'nt produce near the torque of the 6bt. Just a thought.
IMHO, No, you would not.

First, the GM 6.2L Diesel is about 750# fully dressed compared to the Cummins 6BT which is about 1200# dry.

You are correct, the torque from a 6.2L is nowhere near that of a Cummins 6BT.

The 6.2L is about the same size and only slightly heavier than a small block Chevy.
So, if the FSJ frame can handle the size, weight and power from a hot SBC, then the 6.2L is not a problem.

The issue as I understand it is the FSJ frame would not hold up to the excessive weight and the torque from a Cummins 6BT.

[WHSII]

Hello Hoot.

Now before you graft a good J10 bumper on a Ford, Lets talk.

If it is 5 1/2" tall, and in good shape, I might be able to make it worth your while.

Thanks,

[jMedia]

I wrote this the other night but I guess it didnt post:
For what you want to use the rig for Pig Smith, I think you would either have to box the whole frame, or swap the dodge frame underneath (which seems easier *if* you have the tools for it, big IF).
I am now looking towards the 6BT as well, but my Wagoneer would be a daily driver for me and wouldnt be towing anything.
I am anxiously waiting 76FSChiefs build thread :D
And speaking of the rig 76FSChief mentioned, it was done by overlanddiesel at overlanddiesel.com
I emailed the guys asking questions and didnt get too specific answers but this is what they emailed back:

"Hello Josh,

The frame was plated and reinforced in key areas. A crossmember plate was later installed to tie the frame rails together as well as act as a slam-guard for the front differential to oilpan. The Jeep already had a 4" lift but it sagged 2" after only a few months. 2 additional J20 leaves were added to each pack and it hasn't settled since. Hope this helps. Send us pics when you are done! Love seeing other swaps. ......."

And to vintagetrks, the frame needs to be beefed up because of the torque and the weight. The 6bt is a HEFTY engine. IIRC MUCH heavier than the 6.2, exemplified by the sag they mentioned in above email

[seamus]

My 2005 cummins goes through front end parts like crazy,
it's my daily driver spends winters on stock height tires and
summer on 35's.
145000 kms and some parts have been replaced 3 times.
Don't underestimate the forces that these big tourquy
engines produce, and don't forget there is no kill like overkill.

[uglyjeep]

Would you have to beef up the frame for a GM 6.2 swap.

I haven't and I'm not going to.

I'm only a few PS pressure lines, radiator hoses, and a couple of wires short of running my 6.2 in my jeep. My springs aren't sagging considerably more than they were before the 6.2(but they were/are sagging very bad). I have a "custom" set of spring packs (that use the jeep front main leafs and leafs from some unknown trucks rear springs) that I'll put on when I put in my HD44.

Anyway, back to the topic. IMHO, a 6BT would need, at least, some serious reinforcement to the stock frame, even if the engine isn't tuned/hopped up. I think a 6bt would probably turn a stock FSJ frame into a pretzle over time (or very quickly...).

[The PIG Smith]

I know this topic has been brought up before, so I did a search and IMHO, here is the best that I found on this topic:

FSJeeper commenting about FSJ frames:

http://www.ifsja.org/forums/vb/showthread.php?t=20184

http://www.ifsja.org/forums/vb/showthread.php?t=14326&page=2

gotmike's Cummins powered Cherokee and speaks about his frame:
http://www.ifsja.org/forums/vb/showthread.php?t=90702&page=2

[jaber]

I would also like to see where this topic goes....:cool:

[jMedia]

From reading all these threads I think that boxing atleast around the engine bay would be the smart thing to. Possibly throw in a crossmember or some gusseting and you'd be set. Now to find shop prices on frame boxing......

Someone brought up a good point on one thread, how much torque does a slightly build 401 put out? And how much does one weigh?

If only i could find a 5.9 that was under 3grand

[The PIG Smith]

Someone brought up a good point on one thread, how much torque does a slightly build 401 put out? And how much does one weigh?
Excellent point.
It's for sure that a hot 401's weight does not exceed the weight of a 6BT, however the torque is another issue.
Would the torque of a hot 401 put more (or less) stress on a FSJ frame than a stock 6BT with it's massive weight?

[seamus]

Excellent point.
It's for sure that a hot 401's weight does not exceed the weight of a 6BT, however the torque is another issue.
Would the torque of a hot 401 put more (or less) stress on a FSJ frame than a stock 6BT with it's massive weight?


My first gen will weigh over 1100lbs, it will produce over 700 ft/lbs

My daily driver makes over 800 ft/bs

[jMedia]

My first gen will weigh over 1100lbs, it will produce over 700 ft/lbs

My daily driver makes over 800 ft/bs

And your frame? I'm guessing stock. Which makes me happy:) I wonder if the "shake" of a diesel would be a factor as well

[Mikel]

And your frame? I'm guessing stock. Which makes me happy:) I wonder if the "shake" of a diesel would be a factor as well

I just returned from a 300 mile in my 4BT-powered J300. I am utterly amazed at how smooth the engine is (I did raise the idle a bit).

[jMedia]

Dang jealous of that 4bt. Wish I could, stupid CA. Next rig will be pre 76 or if first diesel craps out I'll put a 4bt next

[Hubjeep]

Mikel,
what motor mounts did you use? I have the factory liquid filled mounts in my 4BT CJ and used Benz liquid filled mounts in the Waggy swap (I have yet to start it though).

http://img.photobucket.com/albums/v222/Hubjeep/Wagoneer/DSCN0601.jpg

-John

[710 Burner]

Someone brought up a good point on one thread, how much torque does a slightly build 401 put out? And how much does one weigh?

I think the person to ask would be Ghinmi.

[Greg Taylor]

Would you have to beef up the frame for a GM 6.2 swap. I would think the only reason a fellow would have to beef the frame up for the cummins is the higher torque. Because it would seem to me that the GM 6.2 would be a heavier engine than the 6bt but I'd bet the 6.2 does'nt produce near the torque of the 6bt. Just a thought.

Here are pics of Jim Obey's FSJ buggy with a 6.2L diesel in it. I can ask him if he reinforced the frame at all, or not (guessing not).

FWIW, there have been some pretty serious 401's built for FSJ's, pushing 400+ ft/lbs torque ... and those frames probably were not reinforced.

We even have a IFSJA member (ghinmi (http://www.ifsja.org/forums/vb/member.php?u=7069)) who drag-races a Waggy with a built 500 HP 401 in it ... maybe he can chime in here on how much torque his 401 is making with 500 HP (probably in 550-600 ft/lb range) and if he did anything to the frame. Check it out at http://www.youtube.com/user/ghinmi#p/u/10/7vjJOTC5G3s and http://www.cardomain.com/ride/727760

http://i246.photobucket.com/albums/gg116/amundaza/FSJ%20Buggy/100_2037.jpg

http://i246.photobucket.com/albums/gg116/amundaza/FSJ%20Buggy/100_2038.jpg

http://i246.photobucket.com/albums/gg116/amundaza/FSJ%20Buggy/100_2039.jpg

http://i246.photobucket.com/albums/gg116/amundaza/FSJ%20Buggy/100_2040.jpg

http://i246.photobucket.com/albums/gg116/amundaza/FSJ%20Buggy/100_2041.jpg

http://i246.photobucket.com/albums/gg116/amundaza/FSJ%20Buggy/100_2042.jpg

http://i246.photobucket.com/albums/gg116/amundaza/FSJ%20Buggy/100_2043.jpg

[threepiece188]

I'm not much involved with hi torque and HP but I am interested in this thread from a durability point of view. Is actually deforming a FSJ frame from overload the issue here or is this about developing stress related cracks? Or both?
Dan

[Mikel]

Mikel,
what motor mounts did you use? I have the factory liquid filled mounts in my 4BT CJ and used Benz liquid filled mounts in the Waggy swap (I have yet to start it though).

http://img.photobucket.com/albums/v222/Hubjeep/Wagoneer/DSCN0601.jpg

-John

Hello John,
I used the Lord Fluidlastic mounts that came with the Frito Lay vans, with mounts very similar to yours. Here is an old picture:

http://i305.photobucket.com/albums/nn223/bw1339/My%20J300/DSC03964b.jpg

[Ghinmi]

We even have a IFSJA member (ghinmi (http://www.ifsja.org/forums/vb/member.php?u=7069)) who drag-races a Waggy with a built 500 HP 401 in it ... maybe he can chime in here on how much torque his 401 is making with 500 HP (probably in 550-600 ft/lb range) and if he did anything to the frame.

I still haven't done any modifications to the stock frame. It probably made 550 ft-lb with the old 401 on spray right off the line. Pulled both front tires about the same height. Very little twist.

IMO the front (boxed) part of the frame is pretty strong but the rear not so much. The body is pretty rigid and helps out a lot as long as you've got good body mounts. It's kind of like a unibody/front subframe setup but with a full frame if that makes sense. So far it's worked pretty well for me up to this point. Good luck with the diesel swap!

[CJ the noisemaker]

How about a 4bt?

[Greg Taylor]

I still haven't done any modifications to the stock frame. It probably made 550 ft-lb with the old 401 on spray right off the line. Pulled both front tires about the same height. Very little twist.


Thanks for the good feedback on your experience with the hi-po 401 in there. :thumbsup:

[mr.kowall]

in the last couple of years i drove more then 200000 km in my cummins powered cherokee chief and my brothers j20. both are daily driving cars with the stock frame and both have 6bt engines with tweaked pumps. sure, the fsj frame is not the strongest thing, but i never had probs with it. in my opinion its not necessary to upgrade the frame for a diesel conversion, if your jeep is used on-road or mild off-road.

regards from north germany

http://www.Bildermonster24.de/images/924_chief_21.jpg (http://www.Bildermonster24.de/view-924_chief_21.jpg)

[jMedia]

in the last couple of years i drove more then 200000 km in my cummins powered cherokee chief and my brothers j20. both are daily driving cars with the stock frame and both have 6bt engines with tweaked pumps. sure, the fsj frame is not the strongest thing, but i never had probs with it. in my opinion its not necessary to upgrade the frame for a diesel conversion, if your jeep is used on-road or mild off-road.

regards from north germany

http://www.Bildermonster24.de/images/924_chief_21.jpg (http://www.Bildermonster24.de/view-924_chief_21.jpg)

:D prettttyy. I like. And thank you very much for your input. And thank you Ghinmi. This thread makes me happy:) I believe if you were to do the cummins pigsmith, you would need a little beefing up though because you seem to be using it for a more heaby duty purpose

[The PIG Smith]

:D prettttyy. I like. And thank you very much for your input. And thank you Ghinmi. This thread makes me happy:)
X2

in my opinion its not necessary to upgrade the frame for a diesel conversion, if your jeep is used on-road or mild off-road.
I believe if you were to do the cummins pigsmith, you would need a little beefing up though because you seem to be using it for a more heaby duty purpose
Yes, this is where I am struggling some.
The most stressful activity that I will being doing with a Cummins powered J20 will be towing.
Maybe some light offroading for recovery work, but not hard core offroading.
My guess, it would see payment more than the dirt.
Also, with my flat bed, I feel I am an ideal candidate for a 5th wheel style auto trailer.
So, with a 5th wheel trailer and project strapped down, would be that be considered Heavy Duty Service?
I dunno.

Also, please note that while I maybe asking these questions for my own project, this topic of Frame Strength has been discussed before.
I do not know if I will ever own a 6BT powered J20, so as of today, I am just a dreamer and tire kicker.
I started this thread as an intellectual exercise to bring some focus and possible resolution to this topic.

[The PIG Smith]

in the last couple of years i drove more then 200000 km in my cummins powered cherokee chief and my brothers j20. both are daily driving cars with the stock frame and both have 6bt engines with tweaked pumps. sure, the fsj frame is not the strongest thing, but i never had probs with it. in my opinion its not necessary to upgrade the frame for a diesel conversion, if your jeep is used on-road or mild off-road.

regards from north germany
Welcome to our forum from Fort Wayne, Indiana, USA
Thank you for comments about your Cummins 6BT powered FSJs.

Is this your Cummins 6BT powered Cherokee in this Youtube Video?
http://www.youtube.com/watch?v=i8q4KPP3N2U

[jaber]

Welcome to the forums. Its great to see some feed back from across the sea.:thumbsup:
That is a great looking pic, do you have more posted somewhere for us to drool over? If not, Photobucket is free and very user friendly.

in the last couple of years i drove more then 200000 km in my cummins powered cherokee chief and my brothers j20. both are daily driving cars with the stock frame and both have 6bt engines with tweaked pumps. sure, the fsj frame is not the strongest thing, but i never had probs with it. in my opinion its not necessary to upgrade the frame for a diesel conversion, if your jeep is used on-road or mild off-road.

regards from north germany

http://www.Bildermonster24.de/images/924_chief_21.jpg (http://www.Bildermonster24.de/view-924_chief_21.jpg)

[jeepmj_tj]

I've had mine driving on the road since 07. so far i have not had any frame problems. I made frame plates that utilize 6 or 7 "can remember" of the existing sleeved holes for the engine mounts along with a few welds just to be safe. I had planned to tie these to frame mounts together with an engine crossmember but have yet to do that.

I tow my jeep behind it pretty regularly and now that its summer I will tow my 24 ft pontoon on a weekly basis.

My j20 has the 8400gvw front springs SOA. I have noticed over the last 3 years its has settled slightly but not a whole lot. The engine weight actually made those springs ride quite nice compared to when it had the stock motor.

I eventually also plan to box the rest of the frame whenever i get around to doing my own crewcab conversion.

http://i755.photobucket.com/albums/xx200/jeepmj_tj/1202071610.jpg

http://i755.photobucket.com/albums/xx200/jeepmj_tj/100_1566.jpg

[mr.kowall]

brain and jeff, thanks for the welcome.

yes that my chief on the youtoube link.

@jeepmj_tj - are you thinking what I'm thinking, that cummins jeeps are not happy without trailer??:)

http://www.Bildermonster24.de/images/896_DSC00020.jpg (http://www.Bildermonster24.de/view-896_DSC00020.jpg)

http://www.Bildermonster24.de/images/586_trailerschlampe.jpg (http://www.Bildermonster24.de/view-586_trailerschlampe.jpg)

http://www.Bildermonster24.de/images/857_holgershandy_37_.jpg
(http://www.Bildermonster24.de/view-857_holgershandy_37_.jpg)

[mr.kowall]

http://www.Bildermonster24.de/images/355_holgershandy_21_.jpg (http://www.Bildermonster24.de/view-355_holgershandy_21_.jpg)

http://www.Bildermonster24.de/images/850_DSCF3664.jpg (http://www.Bildermonster24.de/view-850_DSCF3664.jpg)

http://www.Bildermonster24.de/images/335_DSC00172.jpg (http://www.Bildermonster24.de/view-335_DSC00172.jpg)

http://www.Bildermonster24.de/images/691_DSC00164.jpg (http://www.Bildermonster24.de/view-691_DSC00164.jpg)

http://www.Bildermonster24.de/images/621_ddddd.jpg (http://www.Bildermonster24.de/view-621_ddddd.jpg)

sometimes a little bit to fast:) :

http://www.Bildermonster24.de/images/238_DSC00010.jpg (http://www.Bildermonster24.de/view-238_DSC00010.jpg)

http://www.Bildermonster24.de/images/792_mjh.jpg (http://www.Bildermonster24.de/view-792_mjh.jpg)

[jMedia]

woh woh woh ..........
cummins jeep porn overload.
my brain might explode.

Any write ups on your installs? How does the 6bt fit?

[76FSChief]

Very cool to see you on these forums Mr Kowall. When I was considering this swap it was your youtube clips that really sold me on the whole thing. Wont be long till my swap is done, and hopefully I can help people out from my experiences.

Thanks for the pics as well. Good to see that things are holding together well!! :thumbsup:

[The PIG Smith]

woh woh woh ..........
cummins jeep porn overload.
my brain might explode.
OH MY YESSS!!!

...Hmmmm...busty blonde coed or Cummins 6BT powered FSJ.
Well...at this stage of my pathetic life, I'd choose the Diesel Jeep.

Any write ups on your installs? How does the 6bt fit?
Yes, any tips, tricks or secrets to share?
Anything you would not do or would do different?

[Eugene 1]

If you are worried about the frame strength on the FSJ why not use the Ramcharger? The frame its pretty close in WB to the FSj and you would all ready have the Engine mounts there.... just a thought or reinforce the exisiting frame?

[76FSChief]

Based on the info I had gathered when I was first looking into this swap - which by the way Jp magazine lists as one of their 20 worst swaps in this months mag haha - I looked at simply moving the FSJ body to the Dodge frame, but because I had an extended cab I didnt want to cut the frame up. So I looked at the Ramcharger and it looked pretty dam close.

But in the end I decided to just go with the FSJ frame. As I mentioned MR Kowall's youtube videos and the info I got from Overlander diesel convinced me that it could be done with the Jeep frame.

Im not a hard core 4x4er so things should be all good. Time will tell I guess. And additionally sorry I havent got pictures posted for you yet Jmedia - in the middle of mine rescue competition so my time is very limited. Will get something set up soon

[Mikel]

http://www.Bildermonster24.de/images/355_holgershandy_21_.jpg (http://www.Bildermonster24.de/view-355_holgershandy_21_.jpg)

http://www.Bildermonster24.de/images/850_DSCF3664.jpg (http://www.Bildermonster24.de/view-850_DSCF3664.jpg)

http://www.Bildermonster24.de/images/335_DSC00172.jpg (http://www.Bildermonster24.de/view-335_DSC00172.jpg)

http://www.Bildermonster24.de/images/691_DSC00164.jpg (http://www.Bildermonster24.de/view-691_DSC00164.jpg)

http://www.Bildermonster24.de/images/621_ddddd.jpg (http://www.Bildermonster24.de/view-621_ddddd.jpg)

sometimes a little bit to fast:) :

http://www.Bildermonster24.de/images/238_DSC00010.jpg (http://www.Bildermonster24.de/view-238_DSC00010.jpg)

http://www.Bildermonster24.de/images/792_mjh.jpg (http://www.Bildermonster24.de/view-792_mjh.jpg)


More pictures of the two trucks! The more the better!!

PS - Try www.4btswaps.com Lots of 4 and 6BT swap stuff there.

[jMedia]

Based on the info I had gathered when I was first looking into this swap - which by the way Jp magazine lists as one of their 20 worst swaps in this months mag haha - I looked at simply moving the FSJ body to the Dodge frame, but because I had an extended cab I didnt want to cut the frame up. So I looked at the Ramcharger and it looked pretty dam close.

But in the end I decided to just go with the FSJ frame. As I mentioned MR Kowall's youtube videos and the info I got from Overlander diesel convinced me that it could be done with the Jeep frame.

Im not a hard core 4x4er so things should be all good. Time will tell I guess. And additionally sorry I havent got pictures posted for you yet Jmedia - in the middle of mine rescue competition so my time is very limited. Will get something set up soon

No need to apologize :D but wait..why did they rank it as such a bad swap

[cocurtiss]

Go with a dodge frame and drivetrain and drop the fsj body on top of it

[jMedia]

Go with a dodge frame and drivetrain and drop the fsj body on top of it

Easier said than done :p involves cutting the dodge frame and some kinda lift to move the bodies around, not really in my toolbox

[Eugene 1]

Ramcharger

[76FSChief]

I think the reason they rated it such a bad swap is that they mostly deal with the smaller Jeeps - the TJ JK etc etc. I wish they had more info on full size Jeeps, or even better yet if there was a magazine dedicated to the the FSJ!!! :thumbsup:

Back in a week and hopefully get some pictures posted.

[The PIG Smith]

Easier said than done :p involves cutting the dodge frame and some kinda lift to move the bodies around, not really in my toolbox
X2

[jMedia]

I think the reason they rated it such a bad swap is that they mostly deal with the smaller Jeeps - the TJ JK etc etc. I wish they had more info on full size Jeeps, or even better yet if there was a magazine dedicated to the the FSJ!!! :thumbsup:

Back in a week and hopefully get some pictures posted.

Oh ok makes sense, a 6bt may be a bit overkill in a TJ or JK.
Can't wait! :thumbsup: til then I'll drool over mr.kowall video and pics :D

[The PIG Smith]

While it seems from the photographic evidence that a FSJ Frame is strong enough for a Cummins 6BT.

Here is another idea for a the ultimate frame for a FSJ.

There are more than a few folks that make aftermarket frames for Baby Jeeps, CJ, and YJ
There is a custom fab shop here in town that specializes in Jeeps and hard core offroad buggies:
http://www.branikmotorsports.com/index.htm

I've spoken to them about a mandrel bent FSJ frame that will surpass the quality and strength of any OE built frame.
These folks are at all the car and Jeep shows in the area.
Their work and craftsmanship is excellent.

While I do not have an exact price, from the cost of one of there smaller Jeep frames, you need a deep pocket.
They custom build each frame and install all the mounts for engine, axles, steering, etc...so the price is based on the amount of work need for your particular application.

[AMC-J/20]

:D The 89'-93' RAM-250/350 Diesel chassie will fit under it just fine you have to make your own body mounts tho :thumbsup: . . .

That SUV-FSJ looks like its rather large rim's running 19.5's :cool: ?

We need to get some FSJ's on 19.5's :thumbsup::
http://www.ricksontruckwheels.com/customers/


Mike

[Tigger4X]

I stumbled on to this thread by shear stroke of happenstance ... I'm one happy future black smoke blower! :dancingbanana: SUBSCRIBED!!

[threepiece188]

This toppic is an ongoing delima for me as well as I am planning a rather ambitious overland camper crew-cab project although without a diesel.
I would like to know why our beloved truck frames have such a bad reputation by some. I have/had more than fifty FSJ's over the years and I have not noticed any pattern of stress related damage on them. I recall one Wagoneer with a cracked section at the left sway bar mount and a truck that was cracked at the bottom of the third cross-member attaching area but that's all I remember. I have seen several cracked second cross-members, I would not trust those. What have you people noticed?
Dan

[COLOFIREMAN]

My 2 cents here. I would just reenforce the frame if there's a concern. It's far better to not need it then to need and it and not have it. For my 4BT swap I'm not going to use the factory 4BT mounts since they are very beefy and come with there own cross-member to prevent twisting the frame.:thumbsup:

http://i226.photobucket.com/albums/dd218/COLOJEEPGUY2K/4BTmotormounts4.jpg

http://i226.photobucket.com/albums/dd218/COLOJEEPGUY2K/4BTmotormounts.jpg

http://i226.photobucket.com/albums/dd218/COLOJEEPGUY2K/4BTmotormounts3.jpg

http://i226.photobucket.com/albums/dd218/COLOJEEPGUY2K/4BTmotormounts2.jpg

All I'm going to do is cut the mount down and re-weld it to fit within the frame rails....like this.

[The PIG Smith]

My 2 cents here. I would just reenforce the frame if there's a concern. It's far better to not need it then to need and it and not have it.
Jason, this is the $64,000 question.
Is there a concern or not?
Does the FSJ frame need reinforced or replaced with a other style frame or not?
There are opinions each way.

My purpose of this posting is try to answer this very simple question.

[76FSChief]

I should have my 6bt Chief finished soon, and will give you any and all feedback to help you out. I didnt reinforce the frame at all!

[COLOFIREMAN]

Jason, this is the $64,000 question.
Is there a concern or not?
Does the FSJ frame need reinforced or replaced with a other style frame or not?
There are opinions each way.

My purpose of this posting is try to answer this very simple question.

I was agreeing with you.....I pondered this very same thing when I was wanting to swap a diesel. I agree it is a good pre-design concern if one is thinking of a 6BT. This was the main reason I made the more costly choice to go 4BT. I looked at the first gen Dodge frames prior to making this move and found they were the same thickness as a normal 3/4 ton gas truck. So I found Dodge didn't do anything extra to mount the 6Bt within the frame rails. They even tried, unsuccessfully as it turned out, to use a TF727 behind it!:eek: :D

I do believe FSJ frames are very strong, mostly in the later years, and I do think they will hold a 6BT without problems. The main thing that makes me a think this way is the amount of weight that was hauled by all Jeep makes and models since the inception of the brand. Most of them using the un-boxed back area of the frame to hold the weight. As long as a cross-member between the motor mounts and under the motor is used, the only force being exerted on the frame rails is downward when sitting still. So the only thing we all have to think about is torsional load. As you know when accelerating forward torsional load is placed on the frame in the same way as designed from Jeep, although a significant amount more.
Jeep frames are designed to flex which is why it's my opinion that a 6BT will work great in a FSJ. I bought the 4BT with every intention of getting more power to match a stock 6BT's stock output. I bought a new turbo, bigger injectors, turned the VE pump up to match. After a while I asked myself why.:huh: Was it worth the cost, loss of MPG, and sacrifice of engine life to save 400 pounds?? IMO the answer is no. If I had come to this conculsion prior buying my 4BT I would have gone for the 6BT and left it stock. and one more thing to think about. Most of us would like a deer killer front bumper on the front of our FSJ's with a winch. My custom C channel and 5/16 diamond plate bumper with 12,000 old style Ramsey winch is 325 pounds alone.....;) :D

[threepiece188]

My concern is cyclic loading and subsequent fatigue cracks. I have several frames that appear to be in reasonably good shape but I really don't know the history of them. How many miles does it have? What was the truck used for? Was it driven much on un-paved roads? All of these questions will have an effect on the service life of the frame. Reinforcing the frame, particularly boxing will reduce the amount of flex which will improve durability but at the cost of off-road handling. I don't want that if I don't have to. I would like to focus on any problem areas the frames might have. Where are they?

[COLOFIREMAN]

Reinforcing the frame, particularly boxing will reduce the amount of flex which will improve durability but at the cost of off-road handling. I don't want that if I don't have to. I would like to focus on any problem areas the frames might have. Where are they?


Agreed, if we make the frame TOO strong it will force it to crack. Which is kinda funny when that's what we we are trying to stop.... :rolleyes: :D

There are tons of converted old iron on the web with little to no modifications to the frame performed. I for one will not be adding any extra steel to my 88's frame when I install the 4BT.... :thumbsup: ....or if I ever get to it.;) :D

[gotmike]

i think it depends on what you're using it for... i had 14.5" wide tires there for a while and with the weight of the engine i would still break traction before the frame twisted up too hard... but my plan is to be yanking other guys' rigs out of stucks... and running a pto winch up front... for a hiway rig i wouldn't bother changing out the frame... though i might think about some sort of traction bars to keep from tearing up leaf springs...

[Phillips889]

Being a jeep guy I am using the stock j10 frame for my cummins 6bt conversion. I am buying a universal crossmember that has the motor mounts for the cummins fabbed in to it. Their website is avalancheengineering.com I figure with this and the crossmember I bolted to the back of the frame and boxing of course I feel it should hold up. I really don't see how using a dodge frame is easier. I got a free j10 frame and started from the ground up.

[HerrKooled]

If you used a cummins 3500 ram frame, you would essentially have a "J30" with a dana 70 rear (possibly dana 80 if was dually) with a 60 up front, and HD transfer case, suspension and such.

[Tigger4X]

What about the earlier J-truck/Gladiator frames? I'm talking about '64-'74 time spanse.

[COLOFIREMAN]

Wasn't there a company called Avanced Frame Works that would build a FSJ frame that was mandrel bent one piece rails?
I tried to google them but this page comes up ------> http://www.montanajeepframes.com/

I do remember that was the web site but it had alot of picture of FSJ, CJ, and FJ40 frames for sale. Of course this was almost 7 years ago since I looked for them.:rolleyes: :D

[shimniok]

I too remember a company advertising FSJ frames... had various levels of strength up to taller frame rails and fully boxed...

[COLOFIREMAN]

I too remember a company advertising FSJ frames... had various levels of strength up to taller frame rails and fully boxed...

That's the one.:thumbsup: Guess they went out of business.

[bronco23]

i guees its time to kick this thread back up i have a 1990 wogoneer and pulling a 1990 6bt with 66k from a buddy of mine today for 700 bucks so i am going to be starting the build here in the next couple of days would like some advice on where to start on the build cummins is matted to its th727 but i am hoping to just swap tails on them to keep the 4wheel drive from what i can see i need to flip the spring perch and add a few leafs for the load

[gotmike]

or get a divorced t-case...

[bronco23]

i wish i could afford to do full conversion like you did the 1 ton running gear but that can come later as upgrades for now it getting 6bt in and running then to the paint shop body is perfect for now but most of the clear is gone so need to move fast

[bronco23]

or get a divorced t-case... do you have detailed photos on how you mounted the 6bt to the frame :fsj:

[gotmike]

it's the factory dodge mounts... if you want i can take pic's of them... but they should be the same as the one's in the truck you took the engine out of...

[bronco23]

it's the factory dodge mounts... if you want i can take pic's of them... but they should be the same as the one's in the truck you took the engine out of... the motor has actually been mounted to a chevy 3500 dually buddy never finished it i am getting the whole truck for 1500 and pulling motor and selling the rest mabe he used stock dodge mounts ill find out today having problems finding big enough truck to tow it home