final drive re-assembly

[XJkid]

I was trying to locate the cause of some jerkiness at acceleration and separated the final drive ring gear from the case to inspect the ring and pinion. The final drive turned smoothly by hand before disassembly, but when I put the ring gear half back on, it turns herky-jerky, like it is working to get past each individual tooth. I printed off the shaft drive manual from Catatonic Bug's site, but it does not show any special instructions for reassembling the two halves. Did I just screw up a special factory alignment?

[DiverRay]

Yes, you did. The final drive is the same as a differential on a car, and needs to be set up every time it comes apart. I think the instructions are in the 750 final drive Lit. IIRC the 1100 used a modified version of the Lit, but I've not looked in about 8 years. I know I have one good FD in the garage, I just need to look to see if it's a 750 or 1100. They both work, you just need to do a little mod to use the 750. Oh, and the 750 has higher gear ratio, so you turn less RPM's at 75mph.
PM me if you need it.

[XJkid]

But why??

I can accept that I messed something up, nuthin' new to me. I would like to know what I did. I did not remove any shims, the pinion, or anything else. I pulled it apart, looked at the gears, and put it back on with the proper torque. There is only one way for the ring gear side to go back on. Did I not hold my tongue just right as I was putting it back on?

[DiverRay]

Because even though you just pulled the gear and re-installed it "like it was", pulling the gear and re-installing it DOES change the way it mates with the pinion gear. You end up at least 2 thou. off from where it was, and so you need to re-align everything. The gear teeth need to meet just so, or as you now know things will not work well.
That is why I do NOT play with final drives, I just swap if needed. Some people are good at setting them up, but they usually have practice and a lot of time doing it.

[XJkid]

Thanks, Ray!