Help rebuild 8.5 posi

[Newman434]

My rear from my Grand National had been slipping and making noises so I took the differential apart and found my pinon shaft and spider gears worn and my clutch discs are pretty worn out. I want to rebuild it but the GM dealer says the parts are discontinued.

How do I get the parts to rebuild my posi or do I just have to buy an entire unit new?

Also I have already changed the pinion seal and pinion bearing but not quite sure I re-torqued correctly. Whats the proper step to secure the pinion nut?

 

[SSedan64]

My rear from my Grand National had been slipping and making noises so I took the differential apart and found my pinon shaft and spider gears worn and my clutch discs are pretty worn out. I want to rebuild it but the GM dealer says the parts are discontinued.

How do I get the parts to rebuild my posi or do I just have to buy an entire unit new?

Also I have already changed the pinion seal and pinion bearing but not quite sure I re-torqued correctly. Whats the proper step to secure the pinion nut?

GM parts are probably discontinued for the 28 Spline Diff, I think there all 30 Spline now. By the time you buy the Spiders, clutches etc.. you wont be for off the price of a New Diff carrier. Eaton Posi, Yukon Dura-Grip, Detriot/Eaton TrueTrac.
What are your plans for the car? Street, Street/Strip, Strip? You could upgrade to a 30 Spline Carrier & axles for more strength if needed.
8.5" Parts are still available, shop around for best price, ask about package deals, many will meat or beat others prices.
Here's a few places below.
http://completeoffroad.com/
http://www.tomsdifferentials.com/
http://www.drivetrainspecialists.com/index.html
http://www.ringpinion.com/#
http://www.riversidegear.com/

Here's a Diff/Ring & Pinion install Pdf.>> http://www.yukongear.com/Downloads/Technical_Help/Installation_Kit_Instructions.pdf
Pinion Nut, Crush Sleeve & Pinion Bearing Preload Info on Page 10.

 

[Newman434]

This car was meant to be kept completely stock. Was hoping to simply find a rebuild kit but it seems a little harder than I thought. Thanks for the links I will start researching them. If the $ amount is not far off from parts to fix vs new unit I guess I'll just fess up the amount and save some labor.

 

[monzaz]

You will not find stock clutches at any of the aftermarket places anymore either. They bought up almost all the GM stock and now it is gobbled up and gone. The 410409 410408 units are dinosaurs.

You can find a 2 series unit and grab the parts from it to put into your 3 series unit Spider gears (pinion pin gears/ small ones) are the same as the open diffs...Thank goodness. BUT if the side gears are gone junk it. The spider gears kits AGAIN if you can find them are 300+ dollars. 5 years agao I called around and found 3 sets all were 300 + in price. New unit I can get you for 389.00
REconditioned GM unit 259.00

On the pinion nut- if you replaced the bearings then you should have also had to replace the crush sleeve with a new. IF you did not you will have a failure.

The pinion crush sleeve is what helps lock the nut in place along with keeping the bearings seated correctly in their cone races. The preload is set by tightening the pinion nut and crushing the crush sleeve until the bearings are seated at the drag preload listed inthe manual of each rear diff. USually 15-25 INCH POUNDS NOT foot pounds. That is a constant turning drag WITH OUT a carrier in the housing.
Now we do not use a inch pound wrench and after you do so many you get a good feel for the correct drag... This is kind of critical as it is what keep the rear bearings life the longest it can be so do it correct.

TOO loose and you will have noise and ring and pinion failure along with seal failure etc. too tight you will burn the bearings up because of the friction and excessive pressure into the races the bearing are seated in.

Lastly when and if you get all this correct ...STAKE the pinion nut into the thread of the pinion this way the nut will NOT back off uder quick torque stabs on the gas pedal drag racing etc.

Good luck and if you need more help give a call PM me for a number. Jim