Differential

[m-11]

Curious to know if its worth the pain and $$ to rebuild the diffs. The truck I'm re-doing sat in a field for quite a few years. I removed the carrier and there was oil in the rear end. Dirty oil but no water or chunks of metal were present. I'm thinking a good inspection and if I don't see anything obvious, I'll put it back together and run with it. I will need to reseal the yoke so I'll have to read up on that process. I've read about the special tools and things that aren't covered in the manuals. Is this going to be one of those items I will run into troubles doing? I can post some photos of the carrier later.

[isaac_alaska]

sounds like just do the seals and call it good. rebuilding the diff will run you somewhere around $800 these days with new bearings and seals and oil, at least from what i've seen

[ashyers]

I don't know if there's any way to check the fiber thrust washers in the diff with it assembled, but I do know they tend to fail and take out the side and spider gears when things are allowed to rock around in the carrier.

[w30bob]

Hi m-11,

With the diff out I'd get it in the parts washer and clean off all the old gunk. Then you'll want to do a thorough inspection of the bearings. You can't see much, but any signs of rust or pitting on any of the rolling elements is BAD. Rust or pitting will cause stress risers that will destroy the roller in short order. Does the same thing if the races have rust pits, as well as to splines, so check your axles when you pull them out too. The axle housing is vented to the atmosphere, so don't assume just because the differential was in the axle housing that it was protected. When you grab the pinion flange and rotate you should not feel anything other than smooth rotation. Roughness or grinding is bad. Not trying to be a downer with all this stuff, but you've got a great opportunity with the diff out to get yourself some piece of mind if it looks good. You should also be able to see the pinion contact patch on the ring gear......make sure that looks good, and check the backlash while you're at it. If you can't really determine the contact patch you can get some yellow or blue contact patch marker grease at any NAPA for a few bucks and then check it out. Differentials are strange animals.........set up correctly they're practically bullet proof. But if they're just a bit off they'll self destruct if you just look at them funny. Grab some pics for us while you're having fun.............and keep that awful smelling differential lube off your hands!! I would think the lube manufacturers have to work hard at getting something to smell so bad!!



regards,
bob

[MSeriesRebuild]

Half way looking it over and calling it good is bad advice. The post about going through it for $800 is also someone's dream from yesteryear. New bearings of good quality will cost that much. I'll put the facts straight up and out front. Until you disassemble EVERYTHING, you can't do a good inspection. That includes going into the spider gears, side gears, and all thrust washers. This will require breaking open the center section, which does require special tooling. If you see anything that even suggest abnormal wear on teeth, rust pitting anywhere, (gear teeth, bearings, yoke seal surface, etc.,); you have issues that need attention. A differential is far and away the most costly component on the truck to rebuild and set up correctly; if you aren't equipped with proper tooling and know how, then you are in a bad spot for tackling it yourself. All the time, we hear about axle breaking issues. Now there are those who put trucks in abusive situations that will break axle shafts regardless. However in typical applications where breaking axles seems like a plague; the most common cause is worn out side gear and spider gear thrust washers that allow extreme loose motion in the gear set up. Look closely at drive shaft u-joints as well. This excess motion transfers a slapping action to axles causing breakage to become a real issue. Another common complaint is oil leakage at the pinion seal. We have a sealing system that eliminates that issue, so it is much easier to get a positive result with that. Replacing the seal with an NOS one is in 99.9% of cases useless and a waste of time and money.