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DIY Install of a Eaton Detroit Truetrac and Rear End Rebuild

16K views 52 replies 21 participants last post by  WoodButcher 
#1 ·
DIY level: Expert (due to tools required, technical skills needed, repercussion of failures and time allotted)

Run time: ~6 hours (including both wheel bearing seals and both rear brake rebuild)

Eaton Detroit Truetrac Differentials TT70P52571
https://www.summitracing.com/parts/dtl- ... /overview/
USA Standard Gear-Axle rebuild kit ZBKGM75C
http://www.rockauto.com/en/moreinfo.php ... 67&jsn=492



Installing one of these isn't for everyone, but here is why I did it.

When Eaton decided to put there lockers on sale for Christmas and free shipping, I decided that I was going to pony up and jump on that locker train. Although with the bigger K02's and the 233 t case the van was great off road, I wanted the locker for 2 reasons.

1:Our van goes off road pretty much every weekend 7-8 months of the year, and a fair amount of playing in the snow, and in our attempts to "get away from it all" we have become stuck and/or unable to get to where we really wanted to go. We don't have a G80 and used ones were just to expensive for what you were getting.

2:I am installing a LM7 V8 soon, and before doubling(ish) the horse power and torque I wanted to make sure that all of that power was making it to the ground. Not to mention, the v8 was likely able to break the stock G80 if I had decided to get one.

I did this in a shop, with air tools and a lift but the steps will be basically the same even if you were doing it on the ground. I asked a few shops around town what they charged and I got answers from "yeah right" ,"we don't do that here", and prices from $400-1200.

Step 1:Rack the vehicle and secure it. Lift at least the rear of the vehicle off of the ground as the tires will be coming off soon. Do yourself a favor now and put the transmission in neutral now.

Step 2: Remove tires, remove brake drums, and unbolt the rear drive shaft

Step 3: Remove rear diff cover. Its going to be messy. Have a oil catch can ready.


Step 4: Remove the 10mm bolt that holds the spider gear retaining pin in. Remove the retaining pin. You can toss all of these parts in this and the next step if you want. They will not be used in the new diff.




Step 5: now that the spider gears and pin are out, the axles can slide in and out about .75 of an inch. From the hub flange side, push the axle further into the diff. There is a C shaped clip in there that holds the axle in the diff. Once the axle is pushed in, if it didn't fall off already when you pushed the axle in, you will now be able to remove the clip. Remove axle and set aside.







Step 5a: Since I was in there, and I knew my seals were basically toast, and it wouldn't be a rear end rebuild if I wasn't going to do wheel bearings too, I did that too at this point. A pry bar got the seal out. And a slide hammer with a "internal" 3 jaw puller pulled the bearing out. (Before I put the tires back on, I did replace drums, shoes, and all of the components. But since that isn't relevant to this thread, it is being skipped)







Step 6: Mark your end caps. It is important that they go back in exactly the same way they came out. I used a punch to mark them. Once they are off, the diff can come out. It took some prying with a pry bar and a couple of good whacks with a brass hammer. Keep a close eye on the shims that come out. The big ones are directional (and very fragile. DO NOT DROP THEM). Some, if not all of the shims will be reused and it is important that they stay on the side that they came from.









Step 7: Remove the pinion and its bearings. These pictures came out blurry since I had touched the camera lense with gear oil. But basically. Remove the pinion nut, and then beat the pinion into the diff. It will leave the outter races of the bearings in the diff. Use a punch and a hammer to bang these out. There is a shim under the big bearing. Make sure you get it.

Step 8: Now that all of the moving parts are out of the diff. Clean the ever living crap out of the diff housing and don't forget about the axle tubes. I used like 6 cans of brake clean and compressed air to clean everything.

Step 9: Now is a good point to remove your ring gear from the old carrier and install it onto your locker. Press your big bearing onto your pinion(with the shim) and press the diff carrier bearings. Don't forget about locktite for these bolts. Torque is 90ft lbs.




Step 10: Install the outter races of the pinion into the diff and reinstall the pinion. The rebuild kit I got came with 1 new crush sleeve. I got a second one just in case this part got messed up. Also something worth noting, the pinion seal I got in my kit was incorrect. It fit the diff and seals on the yoke, but the outter diameter was to large and prevented the yoke from seating properly. I tried bending the metal part back, but it didn't work. Luckily Napa is only a couple of blocks from here and they had the right seal(glad I brought my old one in since they had 6 different options. Besides... it was lunch time anyways. Once everything was in there came the time to crush the crush sleeve. A dial wrench is needed to do this correctly. Spec for a new setup is 12-15 inch pounds.





Step 11: Install your shiny new locker (don't forget about the shims). Install your end caps and torque to 55 ft lbs. Now comes the tricky part. Setting up of backlash and finding a good wear pattern. The rebuild kit I got from USA Standard Gear came with excellent instructions and provided me with more then enough info figure out how to properly setup these things. Backlash spec is .003-.010. I ended up with a little more then .008 I am ok with that. Now time for painting and finding out the wear pattern. Woot! First try and she looks great! Really wasn't looking forward to taking it all apart again.










Step 12: (if performing step 5a, install new axle bearings and axle seals now)Reinstall the axles in reverse order that they came out. Once the axles are in, the locker comes with 3 pieces that are used to replace the spider gear and retaining pin. Those pictures turned out blurry again so I took pictures of the instruction. Basically, push the axles "out" away from the diff and install the metal cylinder sideways in there. That will keep the axles from being able to move in and drop the c clip. Then install the retainer cap and install the snap ring.




Step 13: Put your drums and tires back on. Install the drive shaft. And install your rear diff cover at 22 ft lbs. Top her off with fluid. Make SURE your fill plug comes out before doing all of this! Would be a lot of wasted time only to find out that you cant fill your basically brand new diff.

Step 14: Verify that all of the time, hard work, and money wasn't wasted and try it out. I opted for dirt, since I wasn't able to rip the tires loose on asphalt. Yup, works!
 
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#52 ·
Wood,yes,no and maybe! Had to get a cup of java, this will take a bit.The 2 proper ways are 1- gut the diff and replace the crush sleeve,2-use the special puller and remove the outer bearing,to replace the sleeve.These rarely worked, and usually get broken easily,to the point dealers would not replace them.I personally have replaced probably close to 300( or maybe more) crush sleeve type diffs front seals without doing either.The key is,be gentle.Many mechanics zip them off and back on with an air gun,giving them a bit more of "crush".This can work,if careful,most are not, and the pinion bearings fail within sometimes a short time.The way I have done it for years-mark the yoke,shaft and nut with a center punch,does not have to be big.Doing all 3 tells you where the nut originally was.Remove yoke and replace seal.Install yoke,nut and washer-install washer same way,and never hurts to put some silicone sealer on washer.Tighten up nut right to the dots,then add a teeny bit more,not really crushing the sleeve more, but adding tension.I could do it easily with an air gun, but if you have doubts,hold the yoke and use long breaker bar.As you are not using a new lock nut,as recommended,make sure the threads are clean and dry,and use red locktite on them.Mechanics have done this many hundreds of thousands of times without problems.What some mechanics do,(I used to) was use an inch pound torque wrench,measure the load,as if you are setting up the diff, then, when putting back together,take it just a little bit more.If you do it that way,can use a new lock nut.But I found nothing gained there,but is better way for inexperienced mechanics.OK,anybody here feel free to offer up.Good luck.
 
#53 ·
Thanks Bob, something along those lines is what I was thinking but not being a wrench I don't know for sure. I may not even replace the seal and just wait to see if it does leak. The van I had this rear in prior was such a leaker it's hard to be certain where the oil came from. At 300,000 when I went out to the van if I didn't see a fresh puddle under it I new it was time to add more.
 
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