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Differential gears/bearing. How to check?

894 views 7 replies 5 participants last post by  LumpyGrits 
#1 ·
Long story short I am thinking of swapping out my stock AMC 20 and Dana 30 ('78 CJ-5) with a Dana 44 and Dana 30 out of another CJ ('74) I picked up cheap (they are correct width). I want the 4.27 gears that the other axles have instead of my 3.73 or 3.54 (I forget which). So, if I do choose to switch them over all I need to do is weld on the correct perches and slap them in (I believe). What I don't know is what shape the "new" axles are in. The previous owner told me they have new ring/pinion with lockers and should be good to go but with no engine in the Jeep I can't test them. I don't know that I could look at bearings or gears and visually know they good. How can I tell if the gears are setup correctly and the bearings are good?

Thanks in advance.

P.S. I would end up removing the lockers in both axles and going back to open rear ends or limited slip.
 
#2 ·
Easy to tell if gears are set up correctly by using the yellow gear marking compound. Look at the pattern in several places around the ring gear. If the gears are not set up correct, it will show you plain and simple. Measure backlash with a dial indicator to see if in spec.

Bearing condition: if you are pulling out the lockers, then just pull everything completely apart and inspect the bearings. Don't wanna pull it apart, then you can do a spin check of the pinion with the diff removed. See how it feels. Should spin smooth as glass, no noise, no rough feeling at all. Should have slight resistance to turning (bearing preload).

When you put everything back together you must get a great pattern, checked in several places, proper backlash and last but not least, .015" preload on the carrier bearings. Do all that and it'll run another 100K miles no sweat.
 
#3 ·
Thanks for the info!

If I take the carrier out to remove the lockers and check the bearings can I put it back in without any additional 'set-up'? Also, if I go one step further and remove the ring gear do I have to do any additional 'set-up' or just bolt it back in and go?

Yep, you guessed it, I'm new to working on rearends.
 
#5 ·
gtx6pack said:
Thanks for the info! If I take the carrier out to remove the lockers and check the bearings can I put it back in without any additional 'set-up'? Also, if I go one step further and remove the ring gear do I have to do any additional 'set-up' or just bolt it back in and go? Yep, you guessed it, I'm new to working on rearends.
It depends entirely on what kind of locker it is. A lunchbox locker replaces the differential spider gears and can be removed without additional set up. A full case locker like a Detroit or arb is a full case locker which means you have to get a new differential carrier to replace the locker with......which requires complete set up.
 
#7 ·
The lockers are the lunch box style, lock-rite I believe. I need to take them out because I use the Jeep almost exclusively for hunting which means I'm on ice and snow a lot and I don't think lockers are right for me.

As far as tire size, I actually have 31" tires. Again, I use the Jeep for hunting and would like the extra gear for steep hills or crawling over logs.

I believe I have to remove the ring gear to get the cross shaft out, if I do that can I just bolt it back on without having to set it up again?
 
#8 ·
If you have never done ring and pinion work before. Let a pro do it and watch what he does, and how he does it.
You need a good amount of special tools from a bearing press to a dial indicator that reads to .001", add in a 1" micrometer too to confirm shim thickness. Along with a inch & foot pound torque wrenches.
I say this as someone who has done R&P work for more than 50 yrs.
OH-BTW, Stay away from 'crush-sleeves' and use a solid spacer on the pinion with shims.
LG
 
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