I agree with the others: Get the drive-side contact pattern correct, and backlash correct. That will seal the future of your gears.
I've set up dozens of rear ends since the 70's. Sometimes you just can't get that bitchen pattern, no matter what you do. I believe sometimes it's the gears, sometimes its the housing/carrier. I think your very first pattern was amongst the best, just didn't like the sharp edge at the root of the patterns. More backlash might help that. On the off-road race cars we sand the edges of the teeth with a small drum sander laid parallel to edge of the teeth to round off any sharp edges on both the ring and the pinion gear teeth. On the high end trophy truck 9/10" diffs, the custom Christman gear set is totally polished, mirror finish.
.055" shim and .008" backlash. Definitely too much shim, coast still has not moved. I'm going to try going to .045" shim, but not tonight. Do you really care what I used to post this message?
I think at .035 is pretty close..Might get a whine on deceleration..Drive side looks like it would like pinion to be deeper but the coast side is already deep..As previous post tltony said sometimes its not going to happen, whether your chuck pinion center line is high or low than ideal or the gears were cut off or the housing and the gears are at the opposite end of acceptable tolerances..You are trying though, so do the more shim and see what happens..Just a note: remove all pattern checker grease [can't think of right name!] and reapply for each check, set [adj] back lash where there is no grease, picky I know...
Pics might be nice. Again, .055" ps and .008" bl Do you really care what I used to post this message?
Put BL to .012..Did you check ring gear for run out at mounting surface? Pattern looks better outside of checking area?
Fabcraft has a nice manual for the Olds/Pont differentials. You might check on getting a copy of it. Has a lot of good history and set up info. IIRC there is a sequence for setting the bearing preload on the carrier bearings. jerry
Thanks Jerry. I do have the Fabcraft book and it is excellent, I just think I got that one gear set that won't cooperate. Then again, it could be the moron interpreting the instructions! Do you really care what I used to post this message?
I just installed a set of fab craft gears in a 9.2 over the winter for my coupe 3.43 I beleive and it took a bit. You said you have a set up bearing,did you hone it to slip on? When you press the actual one one the center race expands about .002-.003 thou and pushes the rollers out changing your depth inward a bit. How much preload are you setting on the carrier bearings? Just a suggestion but whenever I set up a hotchkiss style rear I set the pinion turning torque to recommended specs for a new or used bearing,15-20 pounds inch then with a spanner wrench,not a screwdriver and hammer set the carrier to 30 pounds inch so a combination turning torque at the pinion is 50 pounds inch. The way I was thought at diff school when I worked for chrysler,a gear should respond to shim either hi one one side and low on the other. A backlash issue is either both sides hi or both sides low. If a pattern is perfect on one side and hi or low on the other,there is a problem with the gear. Set the drive she as well as you can and get the coast close. I have done rears where I would bet the farm they would be noisy but was pleasantly surprised. Sticking a pry bar behind the ring gear to put a load while turning can cause a much different pattern than just freewheeling it,as you found. The fabcraft stuff is pricy but it is pretty much the only game in town for 3 series gears. There at least usa made and seem to hold up pretty well.......2 driveshafts later for me at least. Good luck you should be fine. Gary
The Jalopy Journal
