Gears & Axles - causes of gear noise?

What specifically causes gear noise? Is it improper backlash or pinion depth? Or a combination of both? My rear is a 4.10 richmond setup with a Ratech solid pinion spacer. It was nice and quiet while breaking it in, but first time launching it, it developed a whine while on the expressway. The noise is only from 50-75, after 75 it is nice and quiet again. It only does it while accelerating or cruising at a steady speed. If I let off of the gas the noise goes away completely.

Would I need to recheck the pinion preload with the solid pinion spacer in there? Not sure if after break in it needs to be rechecked. I had the gears set up to the specs they were marked for. Here is the pattern after setup… http://geocities.com/duragizer444/images/gears4.jpg

My guess is that the pinion depth is off, but looking for more opinions…
-Jeff

Give the man some info/feedback guys. To be honest, I also wanna know! :emb:

i'm no expert but what i do know is i have did 3 gear diff axle installs on the not so mighty 7.5s including my own and i have a detroit true trac locker with 3.73 gears and it was bad bad loud bad loud like crusing it was louder than my exhaust :( so i was taking the cover off like every sunday after the rases were done to just check for any noticable damage well no damage at all and the back lash was good but i decided to move over one way in this case it was futher from the ring gear and added some royal purple fluid and well it is now very quiet i mean the detroit still pops every once and a while but no ring gear noise at all :) and this 7.5 rear has seen several 1.60 60 foots sence then so maybe i halped yall maybe not but thats what i know

I'd love to know exactly what causes it as well. In your case, Richmonds + 4.10's you should pretty much be expecting gear whine with that setup. If you took a poll on gear whine with richmonds and 4.10's I think you'd find 99% have gear noise.

My research indicates that the hard launches either tweak the setup out of spec or accelerate gear wear in such a fashion that it makes noise sooner than they would under normal conditions.

I think the only way to make sure you don't get gear noise is to never launch the car hard. What fun would that be though?

rich ar epretty loud gears

rich ar epretty loud gears

so i have heard.. but WHY? material, different cut, bad install, all of the above?

Could be both. One of the sites (I foreget which) has a good description of probable causes for different kinds of noise. Google differential terms and you'll probably find it. Basically when you set it up, if done right, you have nice preload, good pinion depth, good backlash. When you load it up on launch, there is a strong tendency for the carrier to shift because neither the housing nor the caps are strong enough to hold it. In all likelihood, you have changed your backlash because of the force shifting it left and if you pull the carrier and adjust it back tighter again you will improve noise situation.