flash_xx

Short story. Switched to 4:10's, shop made a disaster, rear end sounded like grinding stones, took it to another shop, it was a little better but still whined like crazy. Finally after taking the car to two shops I decided to fix the rear end myself.

Upon disassembly, the first thing I noticed was that the pinion nut was so loose It came out by hand, not a good sign. Surprisingly the rear end was fine, nothing broken. Everything is now disassembled and clean.

My only issue is that everything I've read assumes you have a sound starting point for pinion depth and backlash. In my case I can't trust what was in there so I'm basically starting from zero.

I bought the ratech tool for setting the pinion depth and the new gears are Ford Racing (the 4:10's were Motive) How should I proceed with the assembly considering I have no previous point to start from?

tx_zstang

Find the Ford procedures for installing ring and pinion gears.

You say you have the depth too, so with that you should be able to get pinion depth correct. First of all, assume you need to change all 4 bearings (the 2 pinion and the 2 carrier); any or all of them could be messed up now, especially the 2 pinion bearings.
Let's start there, on the pinion. Replace the races with new races, and replace the large pinion bearing on the pinion. The shim under the bearing could be the right one, so you should start from there. Install the pinion and see if the depth is proper.
When you put the pinion nut on, be sure to put some red loctite on the shaft ad tighten to proper pre-loas settings (for new bearings, that's 16-29 inch-pounds of rotation).

For ring gear, replace the bearings, and install and check backlash, adjusting as needed. This can be a time-consuming task, but having a set of digital calipers helps to make equal and proper shim adjustments.
Once the ring gear is in and backlash is right, check the tooth contact pattern (both, simulating 'drive' and 'coast'). If the pattern is good, you're all set! But, the contact pattern may indicate pinion depth issues, and then you have to take it back apart and change the pinion shim under the pinion bearing. PITA, but it gets it done right.

Hope that helps some. It's a bad situation, but, fixable.

flash_xx

Thanks. I bought an extra inner pinion bearing and hollowed it on a lathe so it slip fits on the pinion, I'll use that to try out the different shims before press fitting the new bearing that came with the install kit. Now that I have the slip on bearing it should be much easier to find the pinion depth. Thanks again for the help.