8.5 posi unit, what works???

[rosewood turbo]

Will any GM 10bolt 8.5 posit unit work in our cars or is it G body specific???

[1Badelky]

spline count has to be correct. I think that's all.

[Trbobuick]

Originally Posted by rosewood turbo

Will any GM 10bolt 8.5 posit unit work in our cars or is it G body specific???

any 70-81 f car or 84-87 g car 8.5 posi will work.

[pacecarta]

doesnt matter if its from a 2nd gen F body or a van/truck but to say any 70-81 fbody is wrong
one consideration is 'series' which is based on gear ratio, most second gen Fbodies (birds and TAs) came with 2.56 gears, only the performance optioned TAs got the good ratios (3.08,3.23 and 3.42)
to use your 3.42 ring you need a 3 series carrier , you need to find a carrier that had a 2.73 and up gear, if its lower than 2.73 it is a two series carrier and to use it all you would need a ring gear spacer kit (30bucks at summit) , i wouldnt reccomend a spacer for our turbo cars unless all you are doing is driving it .

spline count is another thing that varies
stock G body is 28
axle spline count on differential units before 1989 were 28,then they went to 30 spline axles. so if you have stock axles (28spline) the newer carriers wont work for you , but they will be great if you racing alot and plan to upgrade to 30 spline axles , if you find a newer 8.5 stay away from gov-loc units




aftermarket eaton carriers use the larger journal side bearings so if you find one of those you need the bearings and races for it

heres a link to clear things up and help in your search
Auburn Positractions Limited-Slip Differentials, don't pay retail!
Automotive Parts Guide for GM 8.5 inch Differentials, Ring & Pinions - Save Money



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[Trbobuick]

The 8.5 out of the trucks is not the same as the 2nd gen f car and the g car 8.5.