I just switched out my 4.10 disc rear for a 3.23 limited slip disc brake rear out of an 86. after I got it all together I added the limited slip gear oil as needed. (it was almost empty) I went for a ride and everything seemed fine. then after parked a day, I noticed a pool of gear oil under the rear, about the size of a dinner plate. ive known these to have leaks, but this seems like a lot. I didn't feel any play in the yoke or axles before I put it in.

could this simply just be a pinion seal leak? should I be checking something else ? I plan to pull the cover and look inside.

I read the thread on the pinion seal replacement, and will do it this weekend.

Check the diff again and check to see if it is actually leaking from the pinion seal or is just leaking from the cover which is a much easier fix. Are you using an aftermarket girdle/cover or is it stock?

Yea, find out where it is coming from first.

im sure its coming from the pinion. ive seen it driping from under the yoke. the rear cover is stock and dry.

Is it leaking from the seal or is it leaking around the pinion nut?

as best as i can see its coming from the seal. its slowly dripping from the edge where the seal would be. i dont see any fluid n the nut.

I guess you know what you have to do.

here is the latest on this.
the pinion nut was loose. after getting the yoke off I found pieces of the pinion bearing cage. the seal was good but I removed it anyway. I took the rear cover off and found more pieces of the bearing. it seems I need to replace the bearing, crush sleeve and so on.
i have mechanical skills and access to a machine shop to press and remove bearings. ive never taken apart a rear end before. ive read a few threads here especially big gear heads threads.
1. can i just replace the bearing shims sleeves and seals on the pinion or do i need to replace everything in the assembly?
2. what is the estimated cost to fix this?

i would like to fix this rear because it is a gu5, posi unit and ive never done one before. is it worth it or is it cheaper to find another rear? i may know where a posi 9 bolt is for around 200

Contact Randy's Ring & Pinion and get a pinion bearing kit. It will have Timken bearings, 2 crush spacers, a pinion seal and a new nut. This is your cheapest way to go. I think you can get the kit with a solid spacer if you want.

Don't just replace one pinion bearing. The preload is different for new and used bearings, so if you mix them then the preload is screwed up. There is a chance that the differential bearings will need to be replaced too, so you might wnat to get the complete installation kit.

I would recommend doing a backlash and contact pattern check before disassembling the rear end. That way you know what you need to shoot for when you put it back together. Take pictures of the pattern on the drive and coast side so you will know what they looked like. There is a chance that the pinion bearing is too far gone to get a good pattern check, but it would be a good idea to have it anyway. Check the backlash in several different places to get an average.

I do appreciate the help.
I talk to a good friend of mine that owns a transmission shop. he recommended that if im going to replace the bearings and all, do the whole rear. im going to drop out the rear, and take it to the shop on a day off this week sometime and tear it apart and rebuild it. he will be there to help me through it. ive never taken a differential apart and assembled it so im looking forward to this.

as for a kit I was advised this is what I need to get:
http://www.jegs.com/i/JEGS+Performan...61223/10002/-1



thoughts or suggestions?

NO. As I've said many time before, do not go to Jeg's or Summit for rear end parts. That kit is just a reboxed Ratech kit, which is one of the worst that you can get. Go to Tom's Differentials or Randy's Ring & Pinion for rear end parts. Their installation kits are much better quality, which will make your job a lot easier.

I was using the link as an example. The kit I found from randys is listed below.

USA Standard Master Overhaul kit for the '82-'99 GM 7.5" and 7.625" differential - ZK GM7.5-B
R1563TAV axle bearing and seal kit, TorringtonBrand, 2.250" OD, 1.400" ID.

I guess I would need two axle kits? it doesn't specify

Go ahead and get the Yukon kit from Randy's. The USA Standard kit has Koyo bearings and the Yukon kit has Timken bearings. The Yukon kit is YK-GM7.5B. The axle bearings that I got from them came 2 to a card. Better check with them to be sure.