• Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

changing front and rear ends


NAXJA Forum User
Hello all I have a 92 xj with 4.0 hp 5 speed that has 3.07 gears and and a 85 xj with 2.5 5 speed with 3.73 gears.the 85 hs a bad motor but the whole front end was rebuilt .and has about 10,000 miles on it will they interchange the 85 to 92 and what diff are there.would like to have the 3.73 .
Pretty sure they will bolt into place, but........ you would lose the Chrysler 8.25 rear to the weaker D35. Also, the front axle (D30) on the '85 would be vacuum operated, unlike the '92. Your '92 will have 3.07 gears, so that would be an upgrade.
I fogot the 85 has 10in rear brakes and the 92 has 9 in dont know if that will a upgrade or not

Swap the passenger axle shaft from the 92 d30 (front) after getting the correct seals from somewhere online and your front will be good, but that may be as much work as simply swapping the gears/carrier.

The 85 shouldn't have 3.73 unless you have the "gas" package or whatever, which is SUPER rare. It's most likely 4.10's from that combination.

Your 92 has a d35, not d30... but anyways, some info: the 92 d35 should be c-clip, while the 85 is the "traditional" style. If what you say about the brakes is true (the older are larger), then the older axle is an upgrade in every way (stronger, easier to repair, more braking power, and deeper gears)!

Everything should swap directly in, but there are three options for the front end (axle shaft) problem:

1. Steal the 92 shaft and get new seals and vac-disco cover plate.
2. Swap gear/carrier from 85 to 92.
3. Posi lock the 85, either with the "perma-lock" or selectable one.

If you're lucky, the 85 has part-time 4wd, then the whole issue is nulled...
swap both axle shafts from the newer one... the 85 likely has cv joints
the 85 I pulled the tag off the read end a fu years ago and it had 3.73 stamped on it .looked it up and said 85 with tow pacage had 3.73 with 2.5. It has ujoints in the front axle i replaced them when it was running about 10.000 on them. the 85 was part time with vac disco. the brakes are 10 in i replaced them the first time they give me 9in had to go back get 10in. Wish the 85 didnt have so much rust i would have just replaced the motor that why i got the 92 had it a yr just turned over 128,600 miles on it have all the paper work from the time it was sold lookes like show room inside ,paint perfect one rust spot about the size of a dime on pass side not thru the paint .give 1500 for it .:)
The 10" brakes on the early D35 are 1 3/4" wide so it's not really an upgrade, it's more of a lateral move, it's the D44 that has the 10x2 1/2" more desireable brakes. If you have new U-joints I'd Posi-Loc the front axle. When discos work right they are a nice setup if you have a 33" or smaller tire and you can run a locker. Remember all YJs came with the disco & most are still running them. Just my opinion.