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Rebuilt My Front Differential (Sort of a How-To)


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****Warning this is by no means a how to but just a diary of the information I learned from my experience rebuilding my front differential and the basic steps of how I did it*****

 

This Saturday I got my friend who is a ASE tech to show me how to rebuild the 8.25 front differential in the SS. Make sure you get a full rebuild kit before starting this job along with pipe thread sealant, and GM anaerobic sealant for the case halfs and new lock tabs. Also you will need a bearing splitter, access to a press, a GM 8.25 side lock adjuster tool, and a carrier bearing puller. Mine has just over 170k on it and its showing its age, its been leaking out of the pinion shaft seal for about a year and the drivers side axle seal since I've owned the truck. Anyways its been making lots and lots of noise and gotten bad enough in the past six months or so that it was way overdue for a rebuild so out it came...

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After the differential was on the floor, I decided to pull it apart of course, this is the part I forgot to take pics because my hands got covered in gear oil. So I'll walk you through it, first drain the oil, next pop the passenger side long axle shaft out with some taps from a hammer. It should pop right out, then remove the bolts holding the extension housing onto the axle, next turn over the axle and pop out the driver side axle shaft with a pry bar or tap it out either way should work. Then remove the bolts holding the case halfs together. The case has two dowel pins which lock it together so to separate the half you have to carefully tap it apart, do not try and pry in the sealing areas unless you want a leak. Once separated you will see the carrier with the ring gear and such. Go ahead and pull the carrier and put it on a work bench. My friend and I first started by using a carrier bearing puller to remove the old carrier bearings. Here you can see how trashed the rollers where on mine and the entire bearing was super super loose.

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After the carrier bearings are removed with the puller, go ahead and reinstall the new ones onto the carrier assembly. Once installed place this to the side in a clean area.

 

Next pop out the side locks, on my diff the drivers side side lock tab was broken off and the adjuster was free to adjust as it felt which is not good!! This should also pop out the bearing races for the carrier bearings.

After you get those out, we can move to the pinion. This is a little more tricky, impact gun off the nut holding on the yoke, then use a puller of your choice to pull the yoke off, then pop out the pinion shaft with a hammer (I think that is what we did at least), once the pinion shaft is removed use a brass punch or a large socket to remove the bearing races. We found these to be really stuck into the case and it took a lot of careful hammering on them to get them to come out. Once removed install the new races for the pinion bearings.

 

This is where the bearing splitter comes into play, install it under the bearing that is left on the pinion shaft and take the setup over to the press. Use the press to press off the bearing on the pinion shaft its pretty straight forward. We used the press again to reinstall the new bearing onto the pinion shaft by dismantling the old bearing of its rollers and outer case to make a nice piece to press the new bearing back onto the shaft. Now you can put the pinion shaft back into the case so that the pressed on bearing is into the new race. Then install a new crush sleeve and install the outer bearing. Install a new pinion seal and make sure the grooves of the area of the yoke splines is clean and free of pipe thread sealant and apply new thread sealant onto the splines. Now install the yoke, washer and nut and snug it down. Next you need to crush the crush sleeve. Use an impact to tighten the nut down in increments and an inch lb gauge to feel the resistance of the spinning of the pinion shaft. You want to achieve 20 in lbs when spinning the pinion with nothing else touching it.

 

Now install the new side lock tabs, reset the lock adjusters, and install the new carrier bearing races into the case halfs. Install the carrier unit with the new bearings into the pinion side case half. Next make sure you case half sealing surfaces are clean and apply a new bead of GM sealant (the red stuff) and put the case halfs back together and bolt them down. This is where the fun begins use the side lock adjusters to set up the lash, it is done by feel on these differentials and by adjusting the side locks you move the ring gear in closer or farther away from the pinion. You want to get this setup just right if not you will wear out the ring and pinion very quick. When you are done adjusting it you want to feel almost no play when spinning the yoke to turn the differential just a very slight bit of a "clunk" just barely. When set correctly you should end up with about 30 in lbs with everything setup correctly. We ended up with 25 in lbs with just the pinion installed and 35 in lbs with everything back together which we where happy with.

 

Finally install the new driver side axle seal and axle shaft, install the extension housing with the GM red sealant and the new passenger axle shaft seal and finally the passenger side axle shaft goes back in.

 

Congrats if you followed by long story of how to rebuild the front differential in your SS you will end up with a great working differential that will make no noise as you drive down the road and turn in parking lots! I am really glad I finally got to do this to my truck it makes it feel like driving a new truck again. I also installed new rear window arms from ebay that pull the windows in more so they seal up better and eliminate the wind noise issue, totally worth it!

 

Good luck if you attempt this rebuild and make sure you have all the parts and tools on hand!

 

 

This is the side lock adjuster we used.

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  • 2 weeks later...

I'm going to be doing this in the near future as well. I was looking under the truck the other day and noticed i had a lot of play in the short driver side axle shaft. I could grab the CV shaft and wiggle the actual axle shaft. Just wondered if that was normal or at least if that how yours was Matt.

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