Beginning to think this gear noise is normal
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Here is a response from Motive Gear themselves, basically explaining my situation. I didn't mention the pinion depth, which went from 0.032 to 0.035 (I think I mentioned that before). Anyway, what are your thoughts? From what was said, 0.007 backlash is quite adequate and apparently, backlash doesn't attribute to gear noise as much?
So, with this said, noise is not uncommon with this ratio and this rear, even though there have been installs resulting in no noise.
Regarding the backlash info, .008 +/- .003 is generally accepted as adequate. It may be written differently, but as long as you were at .007 you are fine. The backlash will affect the oiling/cooling of the gears set, as well as potential noise when shifting if too wide. It will not create a whine in the gear. Gear whine as you described is a product of the differential design, gear design, gear ratio and pinion depth on set-up. Further influencing the ability to hear gear whine is suspension design and isolators, or rubber bushings.
In your case, the Chrysler 9.25 differential design has traditionally been a bit noisy, especially when going to lower gears (higher numerically). The increased rpm of the pinion will often add some noise beyond the stock ratio. I don’t know what pinion shim was ultimately used, but with all of this I am assuming a proper gear install with an acceptable pattern. If this is the case, the gear noise may be unavoidable with the 4.56 ratio.
In your case, the Chrysler 9.25 differential design has traditionally been a bit noisy, especially when going to lower gears (higher numerically). The increased rpm of the pinion will often add some noise beyond the stock ratio. I don’t know what pinion shim was ultimately used, but with all of this I am assuming a proper gear install with an acceptable pattern. If this is the case, the gear noise may be unavoidable with the 4.56 ratio.