rear end noise
 

almost new 4.10 installed in a 12 bolt , noisy when coasting, would this be set up or is it normal ?

Re: rear end noise
 

"Almost new" means they've been set up before and ran for some period of time with that relationship between the ring gear and pinion. They "got used to each other" during that time, and unless you can re-set them to exactly that relationship (and you can't), they will howl. Also, drag race gearsets tend to be set-up for deeper tooth engagement (for durability) and that seldom means a perfect, quiet contact pattern.

Re: rear end noise
 

I like the Chevy 12 bolt. I have installed the 12 bolt housing in a number of drag race buildups. In addition, I have installed many gear sets on both street and race packages.

My experience, about 4.10 and lower, because the pinion becomes smaller and smaller, it is a matter of mechanical tooth contact that the gear set will have some noise. The steeper the ratio, the more noise.

Another bit of experience, for ratios lower than 5.38, the 12 bolt is not the best choice.

A Dana 60 or 9" is a better choice for the steep ratios.

Re: rear end noise
 

Mike-What was your pinion shim thickness and what was your final backlash? Also, used means that a wear pattern has been already established,but how long was it used previously ?Adjusting it a bit and changing the pattern might or might not improve things.

Re: rear end noise
 

.023 pinion and .008 backlash . The gears were in a street car for no very Long

Re: rear end noise
 

That pinion shim sounds a bit too thin.Try a 030" pinion, .008-.010 on the BL is about right.