What gear ratio should I get??

[Big Blue J-10]

Right now I have 35X12.50's on it.i am not sure what the ratio is now but Iknow I will have to re-gear before going with any larger tires.I would like to this if it will not be to expensive.
Danna 44 (front)
AMC 20 (rear)

Adam

[netbear]

I would stick with the 35" tires with the axles
you have. If you drive the truck on the highway
much I would go with 4.11 gears. If this truck is
mostly for around town and off-road with very
limited highway then I would go with 4.56 gears.
Both of these gears sets hold up well if installed
correctly. The 4.89 gears seem to be a bit weak
(tiny pinion) so I would avoid going that low.

If you are doing the gears it is a good time to
install your choice of traction differential
be it Detroit rear/ ARB front (My favorite
combo) or at least limited slip diffs front and
rear to get the most out of your tires and
gears.

[Big Blue J-10]

It sees alot of highway time.do you have to change the axles to or just the ring and pinion? I dont want to upgrade to much until I figuer out if I want to go with the dana 60 and GM 14 bolt.

Adam

[Tad]

You will not be changing the axles, but might be changing the carrier if you have 2.73's in there.
If you have 3.54's, and decide to change them out, I might be interested in your used rear AMC 20 gears.

AMC 20 Gears (http://www.drivetrain.com/amc20.html)

AMC 20 Axle/Gear ID (http://www.ifsja.org/tech/axle/axleid.shtml)

[Big Blue J-10]

thanks for all the info!!!!it might be acouple of weeks before I get the funds(just killed my acount on NEW ball joints this weekend) to even get this started but I will keep you in mind tadsal!

Adam

[Tad]

Cool Adam,
Are you planning to go to Ouray in July?
We are coming right thru Show Low on our way up.

Actually if you find you have 3.73's (which I am not sure were even offered in a J10 in 1980) I would be interested in both the front and rear.
Right now I have a front Dana 44 with 3.54's and a rear AMC 20 with 3.07's (not sure, still covered in grease) one or both are getting changed at some point.

[Big Blue J-10]

Don't know if I will make it, i would really love to though!!!

Adam

[Max Power]

you've got 3.31 if you'vr got a manual tranny, w/ auto tranny 2.73 was standard, 3.31 was an option. If yer runnin 35s you must have 3.31.

good luck with the upgrade... I know you're on a budget like we all are, but if you goto a 37 inch tire and like to 'wheel.. you might want to consider the new stronger axles too, better than fixing it on the trail.

good luck,
Robert

[River Beast]

I would go with a 4.27 to a 4.56.... the carrier in the 44 will have to be changed for sure... not sure where the break is for the 20....

IF ball joints broke the pocketbook... you may need bigger pockets for the gear upgrade..... ;)

Gears will run you around $300 plus master overhaul kits..... then you have to think of the carrier upgrade as well..... on top of that... who will install them....$$$$$$$$$$$$$$$

I spent almost $2K on upgrading my 44's with Detroit lockers and 4.89 gears only to bend them in Ouray.....

My advice.... use what you got... get you a 14FF and D60 and and build them the way you want.....

I have less money in my 14FF and D60 than I spent upgrading my 44's...

[Brown Bear]

Break for the 20 was 3.08 and higher, 2.73 and lower. 44 carrier will def. have to be replaced, and if you've got 3.31 then the 20 will be ok. I figured about $650 for new dana gears, kits, and carrier. Not cheap, by any means.

[Midnightwagon]

id go with the 4.27's they are good for leverage with the 35's and correct the overall ratio to turn those tires to speed and not over speed your motor. but personally ill be going with 4.88-5.13 maybe 5.38 in the new axles for my uses.

[ May 19, 2003, 04:55 AM: Message edited by: Midnightwagon ]

[Big Blue J-10]

The ball joints really broke me because I had a shop do them.I have some friends that should be able to handle the swap for me.save some$$$$.So the 4.27 is my best bet.Is it avalible for the AMC 20?Since all I want to do is swap the gears will I need the master over haul kit?

Adam :confused:

[ May 19, 2003, 12:36 PM: Message edited by: Big Blue J-10 ]

[Brown Bear]

Yes, the kit is necessary. You'll need to bearings and crush sleave and other stuff. Really shouldn't ever do a swap without one.

[Big Blue J-10]

Are the bearings and crush sleave very $$$$??

Adam

[SAustinwag]

nah,
the whole 4.10 kit for my AMC 20 rear was like 400$ including everything. I went ahead and installed positrac while I was in there, I think it cost me an additional 400 er something. But it was well worth it!

[Big Blue J-10]

Did the 4.11s work out good for you or would I be better off with 4.27s??

Adam

[SAustinwag]

I think the 4.10's with 33's are optimal but they do better with the 35's than the 2:70's did this the stock tires. Lots better. I'd prolly go with 4.56's with 35's for serious muddy playing, but for 90% of the time, 4.10's are great. 4.27's might be a happy medium

[Big Blue J-10]

Thanks

Adam

[imported_Big Red]

I am running 4.27s with 35s. Love em. Great on the trails and still cruises at 70 without stressing the engine too much.

[River Beast]

go 4.27's you'll be happier... just like Big Red said....

[Heimeken]

I'll be running 36 or 37" tires. I did the math and on my rig 4.10 will put me back at stock rpms with 37" tires. 36" will give me a bit more power. I have to drive hours to do some good wheeling so I don't want to get too low. I also think it makes a difference if you have an auto or manual tranny.

[Stuka]

Originally posted by Colonel Angus:
you've got 3.31 if you'vr got a manual tranny, w/ auto tranny 2.73 was standard, 3.31 was an option. If yer runnin 35s you must have 3.31.

good luck with the upgrade... I know you're on a budget like we all are, but if you goto a 37 inch tire and like to 'wheel.. you might want to consider the new stronger axles too, better than fixing it on the trail.

good luck,
RobertI didnt read through everything here, but 3.31's were not standard with manuals. My 81 J10 with a T176 has 2.73's.

[River Beast]

Here is a link to a RPM chart I did for manuals and autos.... you can use this to determine where you want to be at 65MPH

RPM Chart (http://home.earthlink.net/~tjnkk/RPMChart.htm)

[ May 21, 2003, 09:46 AM: Message edited by: River Beast ]

[Max Power]

heres the '80 tsm spec page for anyone that cares... my chero is marked in green, the j-10 is lower on the page, J-10s w/ Manual tranny w/ np-208 had 3.31 standard. Not sure what gears were in an '81.

http://www.rbk3.com/fsj/tsm/DSC00004.jpg

additionally heres an interesting rpm grearing chart thats nowhere near as in depth as RBs. But its pretty good

http://www.4wheelparts.com/Tirel_Gear_Ratio.asp

good luck,
Robert

[derf]

I did my own gear ratio calculator (http://www.dfw-tx4wd.org/gears.html) that you can use to figure out what will work best.

4.27's are not available for the AMC20. It goes right from 4.10's to 4.56's.

Stepping up above 3.73's will require a carrier change in the front D44. 2.73's in the AMC 20 required a special carrier. All others (3.08's to 4.88's) use a common carrier.

[Big Blue J-10]

Thanks for all the links and info they have been very helpful!!!

Adam

[Midnightwagon]

looks like the 4.27's are out.

[Hammerx]

http://www.4wheelparts.com/tire_gear_ratio.asp
1 more gear ratio guide.