The last couple of times at the track my drivers side wheel is not spinning during the burnout (stock 10 bolt, 4.10 gears).

Last time out it would not spin when I drove through the water to do my burnout (4500 rpm).

I had to keep it in the water and below 3500 rpm for it to spin on subsequent burnouts.

On the street it will leave tire marks on both sides when I get on it. So it seems like it is beginning to fail. No noise to speak of.

Is it worth changing the posi unit? If so, is it the same process as changing the ring and pinion? Or can I replace it without having to set all of the backlash, spacing etc. I do all of my own work but it seems like this is a specialty install.

Or, do I just replace it with a Moser Ford 9" and a detroit locker?

 

If you are going to keep the stock 7.5 rear end, changing out the differential is relatively simple. If you are keeping your ring and pinion then it's a matter of removing the differential cover, removing the pin and clips that hold the axles out and unbolting four the differential caps. The ring gear has to come off the old differential and put on the new unit so unbolt it before removing the caps. You have to use an indicator to check for coast and drive lash and you will probably need to adjust the side shims to get that correct but it is a simple process. You only need moderate mechanical knowledge and ability to do this. Just be sure to get a 3 series differential. I wasn't careful enough and ended up with a 2 series and spacer.

 

Thanks!

I had heard it was relatively simple, but after looking at the shop manual, I was getting concerned.

I appreciate the response.