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Old 10-28-2012, 03:39 PM
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Torque specs for GM 7 5/8 rear end?

Anyboby have torque specs for the ring gear bolt and the carrier bolts? Also the pinion gear doesn't have any marking for pinion depth. What would the prefered backlash for a 4.56 ratio?

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Old 10-28-2012, 05:54 PM
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Ring gear bolts 65 foot pounds with red Locktite, bearing cap bolts 60 foot pounds with gear oil. Pinion depth is set by reading the contact pattern and making adjustments by what the pattern tells you. This requires several assemblies and disassemblies to get it right. The pinion bearing preload needs to be set correctly for each of the trial assemblies or your readings will not be accurate. Backlash could be anywhere from .003 to .014, depending on how the gears were cut and what brand they are. You really need to know what the manufacturer recommends for backlash.
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Old 10-28-2012, 06:10 PM
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I'm setting this up for a friend. He bought a budget no name brand ring and pinion from jegs and there is no recommended backlash marked on them or in the box. There is what appers to a -99 or -.99 on the pinion head as well as a 4 digit number, 2xxx. I am assuming that should be 2.xxx. I am also assuming that the -.99 would be metric for a little less than a -.004. The etching on these is horrid, bearly readable.
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Old 10-28-2012, 08:05 PM
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Good luck. This is probably not going to turn out well. Those cheap gears are just that, CHEAP. I would go for .007 to .009 for the backlash and make adjustments by what the contact pattern says.
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Old 10-28-2012, 08:51 PM
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I don't think this rear end is going to last very long but he insist on using what he has until he breaks it. 7 5/8 rear end with 29.5 X 10 slicks. It's lasted 7 runs so far with 3.42 gears which is more than I would have gave it.
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Old 10-29-2012, 06:04 AM
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Post pics of the contact pattern if you need help reading them.
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Old 11-02-2012, 11:36 PM
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Quote:
Originally Posted by big gear head View Post
Good luck. This is probably not going to turn out well. Those cheap gears are just that, CHEAP. I would go for .007 to .009 for the backlash and make adjustments by what the contact pattern says.
After washing the gears in solvent before installation the numbers were more readable. Backlash (.oo6) was marked on the ring gear. Ended up with a picture perfect pattern with little trouble. I would have to seen a better selection of shims in their install kit but between the factory shims and the ones in the kit everything turned out OK.
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Old 11-03-2012, 09:21 PM
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GGenerally on the 7.5" GM rear the OEM shim on the stock GM pinion gear (under the bearing) is the right one.
Swap it onto the new pinion and try it. That is your default start point for tooth contact pattern/pinion depth.

Back lash .006" for new gears .006 to .012" for used gears.

With the 4.56:1 ratio the pinion is pretty small so strenth may not be so good and setup will be critical.
up to the 4.10 ratio things are not so dicey. The big weakness of this rear end is the stock OEM differential.
Much more durable with a aftermarket Eaton clutch posi or a aftermaket Auburn cone posi and
correct setup.
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Old 11-03-2012, 09:41 PM
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Actually I using all the original shims however the left side shim is in the right side and vice versa. I've seen some real surprising results from a properly set up 7 5/8 rear ends. There is one in town that held up for 1 summer to an LS motor with a Procharger running 11.0's in a Camaro.
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