What to do with my stock rear end....

[Oakmtnbody]

Ill be ordering the 28 spline Eaton unit and the 8.5 Eaton Posi Ring and Pinion Installation Kit from gbodyparts this week. Im going to wait on the ta girdle cover and reuse stock axles for now.

What's the opinions on being able to reuse the stock 3.42 ring gear and pinion with 21k miles on them with the new posi unit. I mean do you have to worry about a wear pattern being established and having a roar or whine when reassembled. Mine has g87 and no g80 like you guys so what I gather is I need a posi unit , bearings and shims and someone who knows how to set it up?

 

[coach]

What's the opinions on being able to reuse the stock 3.42 ring gear and pinion with 21k miles on them with the new posi unit. I mean do you have to worry about a wear pattern being established and having a roar or whine when reassembled. Mine has g87 and no g80 like you guys so what I gather is I need a posi unit , bearings and shims and someone who knows how to set it up?

The stock gears are very good. You can reuse them.

 

[Tom87GNX]

I was blessed without having the G80 option on my GN.
What have you guys done in this situation? Just get an Eaton unit or should I invest more in building a stronger rear end, axles, etc.
Goals are to eventually have a high 10 second car.

What do you mean by being blessed without the G80 option? How is that a blessing? G80 is merely GM's RPO code for a locking differential. In this car it's not to be confused with the G80 or "grenade 80" associated with S10, and Tahoe units. The GN G80 diffs are clutch type units not factory lockers. Note: not all TR's were equipped with the G80 option, however all 84-87 TR's were in fact equipped with the G87 option, the G87 RPO code is important since that signifies it was equipped with the 8.5 ring gear. The G87 option was only offered on 84-87 TR's and I believe 86-87 Olds 442 models ( not available from the factory in the Hurst Olds). Also the G87 rear in TR's was 3.42 ratio, and the olds G87 has a 3.73 ratio.

 

[Tom87GNX]

The stock gears are very good. You can reuse them.

Just installing a posi unit is easy since you won't have to remove the pinion gear. You simply remove your old unit, install ring gear on posi unit and reinstall. Make sure you install the side shims in the same side they were originally in, this will give you basically the same backlash as before. After bearing caps are torqued I usually apply Prussian blue or similar marking compound to recheck the contact pattern. I've been doing it this way for years, an have assembled about 100 or so rears without any issues.

 

[Oakmtnbody]

Just installing a posi unit is easy since you won't have to remove the pinion gear. You simply remove your old unit, install ring gear on posi unit and reinstall. Make sure you install the side shims in the same side they were originally in, this will give you basically the same backlash as before. After bearing caps are torqued I usually apply Prussian blue or similar marking compound to recheck the contact pattern. I've been doing it this way for years, an have assembled about 100 or so rears without any issues.

Tom if you don't have a OE Posi unit what aftermarket unit would be your choice? The OE units on here go pretty quick where else would be a good place to find used one one. Thanks

 

[SCOOBY DOO]

Eaton are a favorite. I'm running an Auburn Pro Series...and have been beating on it for years.

 

[chopped39]

The Eaton is rebuildable if needed down the road. I usually replace all the bearings and get rid of the crush sleeve and use spacers instead. That way is pinion seal leaks you can just pull off yolk and dont have to worry about changing anything. I went with the Eaton with 30 spline axles and lpw cover with tube braces.The tubes are also welded to housing

 

[Tom87GNX]

Tom if you don't have a OE Posi unit what aftermarket unit would be your choice? The OE units on here go pretty quick where else would be a good place to find used one one. Thanks

I would have to agree that Eaton is the best way to go since it is rebuildable. However the Auburn units seem to hold up well too. All in all I have had very good luck with factory posi's too, of course with that being said they weren't behind a turbo buick either, usually 400-500 HP NA engines.

 

[Tom87GNX]

I would have to agree that Eaton is the best way to go since it is rebuildable. However the Auburn units seem to hold up well too. All in all I have had very good luck with factory posi's too, of course with that being said they weren't behind a turbo buick either, usually 400-500 HP NA engines.

I would probably go with the eaton if you don't have an OE posi. At least you know it will hold up, it is very frustrating to buy a GOOD USED posi to find out its actually worn or already abused to the point it doesn't perform as expected. Eaton is definitely my choice.

 

[Oakmtnbody]

Thanks for all the info I got here. Installed my Eaton posi this weekend and it works great. Did have one problem though, couldn't get all the factory shims back in like you said Tom87. Finally figured out the guy that pressed my carrier bearings on did not seat them all the way down. Quick trip to Harbor Freight, needed a shop press anyway, problem fixed.Thanks again yall.