Axle 3.54 Gear Change Front and Rear from 2:35. I have a Plan

[Beaverseagle]

Hi Everyone,

I've got an 82 SX4 front disco with 2:35s front and rear.  I want to change to a 3.54 or 3:72(?)

I've read a bunch of good info on here about the craziness about how to switch the axle ratios front and rear for those of us with the 2:35 ratio. 

So I think I have a plan.  The rear seems straight forward. I'll probably go with the Chrysler 8.25. I'd like to go with the Ford 8.8, but a bit out of my budget.

The front is going to be a bit harder to figure out. I have a couple of questions about the front:

1. There seems to be a possibility of going to a 3:54 with the 2:35 stock carrier in the front differential on an 82 with a disco.  Has anyone actually done this?  Where did you buy your parts?  Will I need to replace all the bearings if i put in a new ring and pinion set?

2. I have found a couple of sources for just the front differential with a 3:54 but the years don't match.  Can I swap out front differentials from different years?

3.  How critical is it to exactly match up the front and rear ratios.  Would a 3:55 rear and a front 3:54 work?  I also read that not all 3:54 ring and pinion gears are created equally. Some have a different number of teeth.   How closely to I have to pay attention to this when trying to match front and rear?


Questions about the Chrysler 8.25: I have stock wheel bolt pattern. Will my rear wheels mount on to the stock lugs on the Chrysler 8.25 ?

thanks!

[Draekon]

You can swap any year front diff/axle in, but you may need the axle hanger for the axle you are swapping in. There were a few different lengths, so you need to be sure to have the correct one.

3.54/3.55 should work fine. Its close enough to the same and plenty of people run that combo.

[amcfool1]

my take, sorry, keep the Eagle as it is, you want a rock crawler, buy a Jeep, god#$%it, good luck, gz

[Beaverseagle]

Not sure what you mean. Eagles came stock with a 3.54 if you got tge the towing package. Thanks for taking the time to chime in though.

[amcfool1]

hi, not trying to crack on you, you're right, , the 3;54 gears were an option, though personally I have never seen a set, in over 25 years of AMC/Eagle ownership. They came mostly on the 4 cyl. cars, and were no longer available after that, ie, 1983. but, I'm sure there's a few out there still, good luck, gz
Happy Thanksgiving!

[85AmCfreak]

I have a set of 3.54 diffs in my 83 sx-4. Yes they are from a 4 cylinder and yes they are quit rare. Considering the time these cars were produced we were just coming out of a fuel crisis and everything was about economy. I wanna say I've seen and worked on a hundred Eagles in my travels and 80% of them were 2.35 gear ratios. The Eagles towing package if I recall is a 3.08 gear. I'm pretty sure the 2.35 ratio front diff housing will not accept the needed larger carrier assembly to put 3.54 gears in. If you do find the larger carrier assembly Diff housing,what are your intentions with the transmission? The torque flight was the only available automatic and it was only  a 3 speed. I drove my 83 with the 3.54 gears and the 3 speed and needless to say it wasn't fun. You top out at around 60 mph and the motor is screaming. The 6cyl does not have a very high rev limit.

[Beaverseagle]

Thanks for the info.  I haven't given much thought to it. I was thinking about going to a 727 but i understand it eats a lot of  horse power.  I honestly didn't think it would be a huge problem.  I haven't read about people that have done it complaining about that big of top end speed reduction.  I figured I'd loose a bit.  I'm planning to move cross country and i need to be able to tow my VW bus. That's why I'm trying to do this.  I've used some of these gear calculators and they aren't giving me that bad of numbers with a 3.54. Maybe i should go with a 3.08.

I got the tow package info off Wikipedia.

Right now with a 2 inch lift and 235 75 15 tires on a open highway and a head wind i have issues maintaining 65 mph. I figured i need a new gear setup anyway.  However when im on the highway with traffic she does 75 no problems.  If hit any kind of hill that's a different story. 

This kind of unfo really helps.

[amcfool1]

hi, Eagle 258 gears were 2:35, 2:73, and 3:08 for the High Altitude, and trailer towing packages. 3:54 was 4 cyl only, EXCEPT in 1980. There was also a 2year 258 option for HA/auto cars, at 3:31, for 81/82. I think a 3:08 would work better for you than the 3:54. good luck, gz

um why not tow the Eagle with the VW bus?  those things are geared way up there! 'course they also won't break 50mph, lol, again, good luck!