84-86 GN Posi

[skylarkstage1]

The posi option offered by Buick in the 84-86 GN, was the unit Eaton or GM made? If Eaton made, are rebuild kits or upgrades available from the company?

 

[Ormand]

The diff was a GM "corporate" differential, which means it's not a chevy/olds/pontiac/buick diff. Maybe made by Eaton, not sure about that. The discs are available, though, both from GM and from aftermarket. I have no idea whether the same discs will fit the corporate that fit an Eaton. I know that the GM differential uses "S" shaped springs to preload the clutch packs, while the Eatons use little coil springs, about the size of valve springs. When you rebuild one, it is possible to put an extra disc or two on each side, and that makes them lock up sooner, and last longer. Or so I am told.

 

[GNeric]

All of the non-factory Eaton ones we've installed at work are paper or composite clutches. The old GM units are steel discs that have little circular patterns machined into them for bite. The tighter you make them with more clutches or spacers, the sooner they will wear out if you do lots of city driving since the preload puts more clamping on them all the time even with additive. (not talking months time tho) Straight line driving they are "locked" together by the force of the side gears on the spider gears anyway.

 

[buickman68]

call RANDYS RING AND PINION.
they have the best tech advice all the parts in stock as well for your rebuild.
EATON or GM.

 

[Ormand]

I guess it's a trade off. Adding extra discs, and removing shims so that preload stays about the same, would lengthen life, without making the differential slip less easlily. If you add discs, and increase preload, then you will start to lose some of that extra life, until you have less than stock, whatever that might be.