We discovered that the rear diff in my son's '85 was shot (a lot of metal chunks and next to no teeth), so we're getting ready to order some parts for it to have it rebuilt and I have a few questions.

Does this look normal on the ring gear case? I'm not sure if it was damaged or if it was manufactured that way. Do you think it sould be replaced?



Here's a pic of the pinion gear.



Thanks.

 

Thats pretty bad dude! Does this truck have a lift on it that it came out of? This can be caused by the wrong size driveshaft

I had similar marks on the carrier but not on the pinion.

 

I'm about to remove both diffs from my 85. The rear has about 150k on it but the front must have less than 2k (rarely used 4WD). I'm installing TRD elockers front and rear.

If you want one or both of these (stock 4.10 gears) then send me a PM. I wouldn't rebuild what you have as used diffs are pretty reasonable.

 

yeah that carrier looks pretty munched. If you or a friend have a dial indicator set it up with the thimble against the carrier without the ring on it and spin it, runout should not exceed 3-5 thousands difference.

if i were you i would listen to wardamneagle and just look for a used diff, it will be much cheaper than rebuilding that one. If you do rebuild that one you will need to get bearings, shims, ring and pinion, and the carrier. usually the spiders and sides are pretty hard to break.

 

Yes, it has a lift and 35 inch tires. What do you mean by the wrong size drive shaft? I'm guessing it's a factory drive shaft. It has 5:71 gears in it now. Well, at least in the front; the rear is empty.

We have the factory the original differential complete with the factory 4:10 gears. I'm thinking of getting a new 5:71 ring and pinion and a rebuild kit from 4wheelparts.com and swapping over all the 4:10 stuff to 5:71. The one that is broke has a locker in it, but it's messed up too I believe because we found a small spring in with the metal and crap that was cleaned out of the housing.

 

I think the 5:71 is your problem. I thought they were described as being "weak". With 35's you should be running 5:29. Anyone care to correct me?

 

35's and 5:29's are perfect

and from what ive been hearing/seing is that 571's are weak.

 

Here is a good article discussing the strength of 5.71's:
http://www.gearinstalls.com/410suck.htm

Also I am wondering, is that corrosion in there? You guys using a diff breather extension? Swamp water and/or mud getting drawn into the third through the stock diff breather could cause hell in any diff. That pinion looks mangled.

The carrier does look a little beat. I'd take the 4.10 third you have and like you said rebuild it with 5.71's. That locker may be rebuildable too.

Good luck to you.