More gear pattern opioins. Long post

[TheBandit]

JRouche - I've setup a few diffs in the past with success, but I'm no expert either, so take my advise for what it's worth.



First, the pattern looks good to me. It's well centered on the tooth. You might be able to get a clearer pattern by applying more pinion load as you turn the ring gear, but I don't think it will change the results. You mentioned one place having a backlash of 0.095 and if that's really true, you have a problem! I think a chipped tooth on the pinion may cause that sort of backlash.

The wear pattern from actual use you showed in the very first picture may tell a story. The pattern going out toward the heel suggests to me that under load you're getting some movement that you can't produce on the bench. I've read that some people setup pinions deep so that under high loads, the tooth will ride more centered. At any rate, this can happen for a few different reasons. Bearings and bearing preload are the first things I would check. If you don't have a small inch-lb torque wrench, let me know and you can borrow mine (picture here). I don't know the specs on a 9" Ford, but for the 8" Toyota diffs I've setup in the past, you want to see something in the neighborhood of 10in-lb resistance on the pinion without seals or the ring gear in place. In the Toyota diff, bearing preload is a function of the crush sleeve or solid spacer bushings, but I don't know about the 9" so check into it. You also want to see good preload on the carrier bearings, which is harder to measure or produce. I made a large spanner wrench for Toyota diffs and I have cranked on it around 150ft-lb on the carrier retainers to get as much preload as possible. My application was rock crawling and I put my diff through some serious abuse with never a problem. Rereading your post, it looks like you've done this.

That all said, most of the problems with a bad pattern are going to show as gear whine and not "clunk" or "knock" as you've described. You said the diff was whining from the get-go and you've been driving it this way for a while before the knock sound kicked in. Have you been able to inspect the pinion? Are all the teeth intact? Do any of the bearings or gear surfaces show heat discoloration? Is the input yoke/flange tight?