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Discussion Starter · #1 ·
I love these gears that were installed in my 08 bullitt. Big difference from the 3.73's. Anyway as you guys probably have already heard, they're making a humming sound at pretty much all speeds. I've already tighten the pinion nut a little bit...didn't work. Had the backlash tighten a little bit to around 8. I've heard anywhere from 8 to 12 is good... still humming. I also checked with the gear marking material to see if the gears are making good contact with the pinion gear...they are. i wonder if the backlash is set too tight?

Anyway I'm using royal purple gear oil w/o friction modifier. I'm going to add some tomorrow to see if that helps. Also the humming seems to get louder when I turn right...What gives? :angry

By the way I am using new J&M lca's with poly bushings so I expect a little extra noise.
 

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You need to add a bottle of friction modifier. The chatter or groaning is your rear wheels trying to turn at different speeds around a turn. The clutch packs in your "Limited Slip" rear end are not being allowed to slip enough because without the friction modifier they are gripping to tightly. Probably causing excessive wear on the clutch packs and extra stress on all the components.
 

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. . .
Anyway I'm using royal purple gear oil w/o friction modifier. I'm going to add some tomorrow to see if that helps. Also the humming seems to get louder when I turn right...What gives? :angry
. . . ..
yep, friction modifier is required as I understand it -- even with the oils that say the friction modifier is already in there
 

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Discussion Starter · #5 ·
Thanks for all the input. It seems like the actual diff isnt in the housing tight enough. Currently in the shop doing the install for a fifth time... lol:laugh:
 
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