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Backlash
I've read anywhere between 0.008-0.012. Not sure if tight or loose is better for racing
Pinion Depth
Does everyone setup their pinion depth for a wear pattern in the middle of the gear, or do you favor the heel or toe of the gear?
Pinion Drag
I've seen anywhere between 16-24 in-lbs on a new bearing... High side or low side of that range??
Backlash- I set my backlash at .005 -.008 (gm)
Pinion depth- get a nice middle pattern. Too deep too shallow is bad! Too much toe too much heal is also bad. You have a coast pattern on the back of the gear and you have a thrust pattern on the front of the gear look at both.
I am a high side man. New bearings will break in and loosen up slightly.
Take your time
Make sure all bearings race are fully seated! if not its all for nothing!
My two cents
I talked to one of the tech guys at Richmond a fair bit about setting up my own gears this time around (used a local shop for all my previous rebuilds). Here's what I learned:
Backlash - the GM spec for mine is .006 - .010. Richmond basically says for "oval track racing without a diff cooler", you want .010 - .014. The normal target for street / strip applications is .007. They didn't have any specific recommendations for road racing but figured it would be pretty close to what you'd want for oval track stuff. I set mine up at .010, mostly because that gave a nice even pattern with the pinion shim stack I used (.030).
Pinion bearing pre-load - GM spec is 12-15 in/lbs for new bearings. Richmond said 8-12 for racing but I ended up at 15 with the pinion nut torqued to 125 ft/lbs, which is the spec for the solid spacer I used. In my last kaboom, I'm fairly certain some axle hop I had on Friday compressed the crush sleeve, which pulled the pinion deeper into the gear and resulted in a lot of work and foul language. There was ~1/8" of slop in the pinion when I pulled it apart. It took a few hours to get the shim stack "close enough" on the solid spacer but it will hopefully help it last a little longer. Or not...it's still just a little 10-bolt made from recycled beer bottles.
Carrier bearing pre-load - once the pinion pre-load is set, you want to install the carrier, torque it to spec, and measure the pre-load again. You're looking for it to increase by about the same amount as the pinion pre-load divided by the rear ratio, which is around 3-5 additional in/lbs depending on your gearing.
Wear pattern - middle of the gear on both the drive and coast sides. You're mostly looking to get them even to each other and centered on the gear.
Other than that, I also learned / remembered to use teflon paste or thread sealer on the pinion splines, RTV on the outside of the pinion seal, and NOT to use synthetic diff fluid with a Tru-Trac.
Have fun!
MarshallQuote:
Originally Posted by marshall_mosty
First need to be aware the tolerances are specific to a rear end rather than general but generally speaking toward the tighter side is better due to the heat we generate versus a road car. For the 8.8 I set backlash closer to .008" and turning torq around 24inlbs according to my right wrist.
Exactly ;)Quote:
Originally Posted by Trublu