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8.25 Rear End Help

LaredoBucket

NAXJA Forum User
Hey all,

My Pinion bearings in my 97 29 spline 3.07 gear 8.25 rear went belly up. I found a 98 29 spline 3.55 gear 8.25 rear end at the junk yard, it was missing the axles and the spider gears and shims fell out. Can I use my existing axles & carrier in the new rear end, if i swap the ring gears to use in the new axle?? Is this an easy fix??
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my XJ is a 92, 5 speed 2WD with 97 8.25 rear end 3.07 gears, 4.5" lift, running 32 BFGs
 
You cannot mix a 3.07 ring gear with a 3.55 pinion gear. They won't mesh right. Ring and pinion gears even of the same gear ratio are machined as a matched set so they must be kept together. A ring gear without a matching pinion gear or vice versa is junk. A 3.55 junk yard axle won't do you much good. You need to find a junk yard 3.07 axle or have your existing 3.07 axle rebuilt. Changing pinion bearings is not as hard as regearing but still requires enough tools to R/R the existing bearings and set it up right.
 
You cannot mix a 3.07 ring gear with a 3.55 pinion gear. They won't mesh right. Ring and pinion gears even of the same gear ratio are machined as a matched set so they must be kept together. A ring gear without a matching pinion gear or vice versa is junk. A 3.55 junk yard axle won't do you much good. You need to find a junk yard 3.07 axle or have your existing 3.07 axle rebuilt. Changing pinion bearings is not as hard as regearing but still requires enough tools to R/R the existing bearings and set it up right.

ok, so I went to the JY and bought an 8.25 27 spline with 3.55 gears. Would I be able to swap my in my 29 spline axles, carrier and swap the ring gear so it all matches up to the pinion?
 
ok, so I went to the JY and bought an 8.25 27 spline with 3.55 gears. Would I be able to swap my in my 29 spline axles, carrier and swap the ring gear so it all matches up to the pinion?

no.

as was explained to you, the pinion and ring gear are a matched set.

You can't simply swap carriers without setting up gears anyway.

If you are incapable of setting up gears your best bet is to go get a matching pair of 3.55 auto axles and simply swap the pair.

with your 32's that will put you back to nearly stock gearing anyway.
FWIW 3.55's and 30's is stock gearing with a 5 speed.
There is 0 reason to want to stay with 3.07s with your current setup.
4.10's would actually be more appropriate, but you can't just go and grab those out of nearly every auto XJ on the planet.
 
You would still have to swap the pinion. Why didn't you just get new pinion bearings?

Well to tell you the truth I wanted an 8.25 with better gears than 3.07. It only cost me $180. My old 8.25 is a 29 spline with 3.07 gears. I'd like to upgrade the axles in the NEW 8.25 27 spline to my 29 spline axles. I thought maybe if I swapped in my old 29 spline carrier, reusing the NEW Rear end and ring & pinion gears, I thought I could probably have an 8.25 with 29 spline and 3.55 gears. I'm fine with running the NEW rear end as is. (8.25, 27 spline, 3.55 gears)
 
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Leave the ring gears alone. AFAIK you should be able to swap the axles/spider gears from the 29 spline with the 27 spline parts.
 
no.

as was explained to you, the pinion and ring gear are a matched set.

You can't simply swap carriers without setting up gears anyway.

If you are incapable of setting up gears your best bet is to go get a matching pair of 3.55 auto axles and simply swap the pair.

with your 32's that will put you back to nearly stock gearing anyway.
FWIW 3.55's and 30's is stock gearing with a 5 speed.
There is 0 reason to want to stay with 3.07s with your current setup.
4.10's would actually be more appropriate, but you can't just go and grab those out of nearly every auto XJ on the planet.

Yeah, I know the ring and pinion must be matched. I don't think my question was clear enough.

Ok, I figured it might have to be set up properly with the right tools and such... wasn't too sure if it was simple or not, just thought I'd ask.

Maybe I will keep my 29 spline axle shafts for up grade in the future. I also saw a Limited slip carrier for sale that I may pick up. it would be cool to have better traction off-road.

Thank for your you help and advice! Cheers!
 
You don't need to remove the ring and pinion from the axle housing to change to 29 spline axles. The new axle assembly has the ring & pinion ratio you want so leave the ring, pinion, and differential carrier alone. All you should have to do is remove the axles and spider gears from your old axle housing and swap them into your new axle housing. Then remove the old axle assembly from your Jeep and install the new one.
 
if my recollection is correct the 29 spline carrier is different. The side gear area is bored larger to accommodate the 29 spline shafts and side gears.

so no, you can't just swap the spiders. The carrier is different.
 
if my recollection is correct the 29 spline carrier is different. The side gear area is bored larger to accommodate the 29 spline shafts and side gears.

so no, you can't just swap the spiders. The carrier is different.

Okay. That was the only part I wasn't sure of.
 
just swap that 27 spline in and run it. They're not terrible. Still miles better than a D35 housing.

keep your eyes open for a 29 to replace it with, or rebuild yours after it's out of the jeep.
 
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