Rear question

[ScottH]

Can anyone tell me if a 12 bolt posi unit from a 72 leaf spring truck be swapped into a 12 bolt coil rear in a 68?

Thanks.

[gonebad2]

I think you ccan do it by swapping the perches from the 68 to the 72

[Longhorn Man]

I think Classic Enterprises sells a kit of sorts for the panhard bar.

[ScottH]

Thanks for the info.

I was thinking more of just swapping the "guts" rather than the entire rear.

Would this work?

[Mike C]

Yes, it will work. Probably. What gear ratio is in the 68? What gear ratio is in the '72? If I had to guess, I'd say 3.73 were in the '68 and 3.07 in the 72 in which case NO. The Pickup 12 bolt uses 2 different carriers, one for 3.42 and smaller numeric gear sets and the other for 3.73 and higher numeric gear sets. You can run a ring gear spacer to go from the 3.07 gear set to 3.73, but not the other way. This is an adequate solution for a moderate to low power application. I have a 2.73-3.42 posi in the back of my Jimmy with a set of Richmond "thick" 4.10 gears. Basically the gear is built with extra material the thickness of the spacer. But if you buy a gear set, it will need to be professionally installed to get the correct pinion depth. If you just swap the carrier into your other axle, a cheap magnetic base and dial indicator can be used along with an aftermarket shim set to restore backlash to its proper setting. Just measure the backlash in the 68 gear set, and then when the posi is swapped in, adjust the shim sets to restore backlash. You should be able to find some internet info on setting up backlash, or it is covered in the GM overhaul manual. FWIW, the overhaul manual is the best book I ever bought.