Putting in 3.73s in a couple of weeks. Few questions...
- Thread starter jchristena
- Start date
Well, I do believe I have this solved. I tore it down the night of my followup post(Tuesday I think?) and re-measured the backlash. It had opened up to .012. So, either I ****ed up and read the dial back indicator wrong the first time, or it opened up(which shouldn't happen w/ the already broken-in/worn bearings you'd think). Either way, here's the deal.
My factory shims were really close. .275 driver's and .277 passenger's. I swapped these to be .277 driver's and .275 passenger's to achieve what I THOUGHT was .008. Given that it was .012 when I tore it back down, for whatever reason, I had to reshim. Keep in mind my total shim thickness, which gave whatever the quiet factory preload was, was .552.
I setup my gears this time a little tighter than spec. .006 backlash. I know this is tight but I've had good luck w/ this before. I ended up with .557 overall thickness this time which obviously increases overall bearing preload a bit. I think after beating on it, I'll be right at .008.
When I drove it, it was immediately substantially quieter. I think the backlash had a little to do w/ this but mainly I think it was the increase in preload. Initially, there was some bearing noise but that has quieted down substantially after about 200 miles and several heat/cool cycles. And the best part is I reused the same gears. Yea, they only had 20-30 miles on them but you could see the wear pattern on the gears and it looked good.
Bottom line, as others have said, I think more carrier bearing preload is better rather than too little. YMMV, but sometimes it works out.
My factory shims were really close. .275 driver's and .277 passenger's. I swapped these to be .277 driver's and .275 passenger's to achieve what I THOUGHT was .008. Given that it was .012 when I tore it back down, for whatever reason, I had to reshim. Keep in mind my total shim thickness, which gave whatever the quiet factory preload was, was .552.
I setup my gears this time a little tighter than spec. .006 backlash. I know this is tight but I've had good luck w/ this before. I ended up with .557 overall thickness this time which obviously increases overall bearing preload a bit. I think after beating on it, I'll be right at .008.
When I drove it, it was immediately substantially quieter. I think the backlash had a little to do w/ this but mainly I think it was the increase in preload. Initially, there was some bearing noise but that has quieted down substantially after about 200 miles and several heat/cool cycles. And the best part is I reused the same gears. Yea, they only had 20-30 miles on them but you could see the wear pattern on the gears and it looked good.
Bottom line, as others have said, I think more carrier bearing preload is better rather than too little. YMMV, but sometimes it works out.
Different part numbers on the same gears mean it's slightly different metal for racing (high temp) or street.
There are different preloads for new bearings and old bearings because new bearings will wear in and loosen up, decreasing the preload.
There are different preloads for new bearings and old bearings because new bearings will wear in and loosen up, decreasing the preload.
Oh, something i just thought of... can someone annoyed with the whine try getting noise cancelling headphones and just turn them on (while in your ears) without playing music through therm? I was thinking about figuring out how to use the bose noise cancelling radio chip or get an EE friend of mine to build me noise cancelling speakers... but forgot noise cancelling headphones are ready made.
When I first did my 8.8 it was perfect. Weld tubes, 9" ends, bearing support cover, solid bushing, Moser axles, ... silent for 400 miles. Went to the track and completed some mediocor runs and the next day the gears were whiney. The BL opened up to .014", I think. After many attempts, w/o success, I installed a 9".
Good luck.
NIXDSG
Good luck.
NIXDSG
Great info! Thanks for posting and good job.
When you use the term "carrier bearing preload", you are basically referring to the amount of shims on either side of the carrier, correct? And you ended up deducing that less backlash resulted in quieter whine, correct? Do you still notice some whine or is it now perfectly quiet??
How about the torque preload on the pinion bearings? Did you measure that, or did you change it?
I notice zero whine now. Initially I noticed a little due to the wear pattern on the gears(those first 30 miles). I also noticed some initial bearing noise. That all seems to be gone now. It is quieter than the factory setup with a TON less slop.
So, yea...preload = more carrier bearing shims. Essentially you are preloading the bearing on each side of the carrier by taking up space.
I'd have to go back to another post, but I think I measured pinion preload at 22lb-ft. The factory manual has a wide range there IIRC...like 12-25lb ft. Basically, no slop at all but not too tight.
So, yea...preload = more carrier bearing shims. Essentially you are preloading the bearing on each side of the carrier by taking up space.
I'd have to go back to another post, but I think I measured pinion preload at 22lb-ft. The factory manual has a wide range there IIRC...like 12-25lb ft. Basically, no slop at all but not too tight.
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