rear axle swap

[warlordxx]

I have a 85 GMC 2wd 10 bolt 3.08 and I found a rear out of a 72 2wd with I think a 12 bolt with 3.45? and a posi will this drop right in? what style posi would this be? its a stock gm posi so a cluch or cone style? will my backing plates bolt on the 12 bolt or do I need to buy new brakes... mine have about 200 miles on them.
I can pick this rear up for 75 bucks so even if it wont fit I can get my cash back just for the posi
if this wont fit what years use the same axle I know the 88 up the springs are set out wider

Thanks

[mrjohnwayne]

hmm not sure if 72 will fit under 85 or not. anything 73-87 will fit though. and not sure but 72 and prior all used dana rearends (i believe...)

[dunebound69]

I think the 72 is set up for the coil spring rear so you would need to cut off mounts, weld on new ones. That is no big deal though. The bold pattern could be different at the hub. When all else fails use a tape measure. The other thing is the u-joint.

[gmctrucks]

Originally Posted by dunebound69

I think the 72 is set up for the coil spring rear so you would need to cut off mounts, weld on new ones. That is no big deal though. The bold pattern could be different at the hub. When all else fails use a tape measure. The other thing is the u-joint.

I had my front spindles re-machined on my 57 F100 so that the front bolt pattern would fit the newer rearend that I placed on it also Napa should be able to find you the correct U-Joint first check everything first the way your doing. Or get a rearend off a 73-87 Suburban.
Good luck! GMC

[lifted84k10]

the 2wd rearend is set up with trailering arms and coil springs like mrjohnwayne said

[hotrodpc]

As Lifted and Johnwayne said, those are coil spring trucks as standard equipment, but I have also seen them in leaf spring suspension. I had a 64 GMC that was leaf, and a neighbor had a 72 that was leaf. We thought we were special because everyone else had coils.