231/300 Doubler..

[cajun_lad]

Has anyone tired running the np231/dana 300 doubler setup in these big rigs? I was just playing around with the gear ratio calculator and got some mad numbers. And the adapter is way cheaper than a 203/205 adapter. Plus, unless I am mistaken, won't most trannys that are in front of a 231 bolt to our engines? Thoughts?

[misfittom138]

You talking about that box for rocks set up? I was thinking about using that with the 208 I have. Would be nice. I hear it works great.

[cajun_lad]

Yeah, with the 2.72:1 low range from a np231, that beats the 2:1 from a 203. Plus you don't have all the hassle of mating the 203 to a tranny that will bolt to the amc v8. If you upgrade the d300 to HD 32 spline front and rear o/p's, I don't see why this wouldn't be a very doable option. Has anybody even tried this setup in an FSJ?

[JeepsAndGuns]

If I was gonna run this in a FSJ, I would probably find a 231HD. That way you get the stronger 6 pinion planatary gear set. IIRC, the standard 231 uses a 4 pinion. I think the 231HD comes in some later model dodge 1/2 ton's.

[misfittom138]

I have a 231 not being used. I'm really thinking about trying it. Going super low and keeping highway gears sounds lik the best part of the whole set up! :D

[cajun_lad]

What trans would you use with the 231?

[rustywagoneers_com]

Just to get the info in the hands of those who might care....

stick a GM (slip-yoke style) output shaft into an FSJ 208 (or swap GM trans and 208 / 241)

GM 32 spline NP205 (TH400 or SM465) slides right onto the output shaft.

http://www.ifsja.org/forums/vb/showthread.php?t=75260&highlight=32+spline

peace
Dave

[cajun_lad]

Are you saying use the whole 208 case mated to an entire 205 case? So basically you would have a front O/P on both pass and driver's sides? If you have done this, show me a pic please, cause I am :confused: !!

[addicted]

Just to get the info in the hands of those who might care....

stick a GM (slip-yoke style) output shaft into an FSJ 208 (or swap GM trans and 208 / 241)

GM 32 spline NP205 (TH400 or SM465) slides right onto the output shaft.

http://www.ifsja.org/forums/vb/showthread.php?t=75260&highlight=32+spline

peace
Dave

That is a pretty sweet idea for a pretty easy doubler. THe hardest part would have to be fabbing up a spacer between the two cases. Then you would neen one big cross member or two of them conected by a smooth skid plate. My only concern would be the two torqueing against each other and possibly breaking the aluminum 208 case.

[rustywagoneers_com]

You would cut and plate the 208.
(or, run a driver drop 208, and a pass drop 205, if you wanted to go cheap)

Ford and TH400 / SM465 205's all use the big input bearing, so pass drop / driver drop is pretty easy to shange, if necessary.

[rustywagoneers_com]

Also... Ford slip-yoke 208's (slightly rare) are 31-spline out, and the exact same spline as the Ford 205 input


further... GM (from TH350 and 700 applications) and XJ 231's and 207's use a 27-spline output, which is the same as the GM TH350 / 700 27 spline input. Which means... a GM 208, 241, 231, or 205 (with 27 spline input - as in, from behind a TH350, or a 700) will spline right onto the back of an XJ or GM 231 or 207.

[cajun_lad]

Maybe I should have entitled this thead, what are all the easy ways to make a doubler?
Back to the point though, if you have a dana 300 on hand and want to double it out, will the cheaper route of np231 crawl box work on our FSJ's? The crawl ratio is way better than putting a np203 in front, and the setup is cheaper. But would it hold up in a full size rig is my main concern?

[rustywagoneers_com]

Sorry for the confusion. Last post here and I will stop messing up your thread. HONEST

Apparently Duffy is harder to get a hold of than ever before, so getting a 'Box 4 Rocks' kit is probably going to be iimpossible from now on. It also appears that Mad Rooster is done (or might be done) making parts for the 231 / 300 doubler kits. SO. If you are going to do it, you will have to do what lots of guys do, and get the output shaft of the 231 cut and resplined to go into the 300.

Personally, I think a 300 is gonna be taxed pretty hard in an FSJ, in a non-doubler application. So when you put 2.6 or 2.7 TIMES as much torque into it, I think a 300 is even less likely to live. 300 and 20 are fairly equal strength wise. And 20's are fairly quick to go bang when an FSJ gets big axles, big motor and big tires...

If you found a 6 pinion planetary for the 231, or used a 241 planetary in the 231 front half, I think those parts would live nearly forever as the front half of a doubler... it becomes a question of your cut /splined stock shaft, or your welded doubler shaft, or your D300 going nuke.

Personally, I would sell the 300 for a few bucks and use that to do a 208-into 205 or 231 into 205. Especially in a rig with a little WB to play with.

Cheapest setup I can think of off hand would be 23 spline 231, into a 27 spline (small input - TH350) NP205. Since the 27 spline only fits Th350's (stock) it will be one of the cheaper 205's to buy. It will last pretty much forever. Costs the same to upgrade as a 300 (big shafts and yokes anyway).


I do need to clarify some info I posted above on the GM 231 / 207 where I was a little fuzzy. I apologize for doing it here, but I figure I better fix it where I made it confusing.... The GM231 and 207 cases have the same 27 spline output as the XJ 231 and 207 (slip-yoke style) cases.

A T-case (208, 203, 205) from BEHIND a TH350 or TH700 will go BEHIND an XJ231, XJ207 GM207 or a GM231

[misfittom138]

I can't think of a single reason why it wouldn't. And if I do it, I'm keeping my 727. It will work with it and after how much money and time I spent rebuilding it, no way am I swapping it. Guys on pirate run the 231 doubler with chevy 350s and what not from what I saw. So why wouldn't it hold up? It's just the front half of the 231 and only adds 6to6.5 inches to driveline. I would love to try it out.