Finally got a posi

[BIGBLU 72]

I picked up a posi rear end out of a 68 today with 373 gears! It turned super easy and the springs in the posi unit still have the yellow paint on them! I paid 250 for the whole setup! The rearend is leaf but my truck is coil so will it be easier to swap the guts or modify the rearend the fit in the truck?

[Mike C]

Swap the guts. If I was in your situation, I would buy a universal pinion depth checker from Summit or Jegs. About $100. Then I would measure the new rear for pinion depth and backlash. You then need to re-create those numbers in your existing housing when you swap the gears. This is the way to do it correctly.

You can run a pattern with marking compund and then swap guts and try to run it again and match it, but that is sketchy at best IMO, and I have setup probably 25 different diffs. I still find reading the pattern is tough, even after applying a load to the axles when rotating the pinion.

The third option is just swap and hope. I did this early on in my rear axle career and found that the housings are pretty close. Close enough? Can't answer that, but it worked for me in a couple of instances.

[dhaymaker]

There is significantly more work in making a leaf-to-coil swap than using the pinion depth and backlash method, IMO. But, then again, I'm kind of a numbers guy, even though we've used the marking compound and pattern method before. Just take your time, get some good measurements and transfer to the new parts to the original housing! Good luck!!