New Motive 3.73's making noise only on coast? Can anyone tell me what would cause this? It is loudest at about 40MPH, I let off the gas completely and it buzzez. I have NO noise when on part throttle or heavy throttle, I only drove the car for 2 minutes because I did not want to damage anything. I also replaced the posi unit with the Auburn Pro Series. Any advice?

 

my guess would be either you didn't set them up right, or you put a bearing in dry.

 

they are not set up right

 

I was stupid and took my TA to the local dealer to have them install the new posi, gears, and Moser axles, I should have done it myself. I picked it up and there was a slight hum all the time. It was not bad, but it was there. After around 50 miles or so the hum became quiet almost non-exsistant on excel and decelleration, and just barely audible while cruising between 40-50mph. I am thinking that as I get some miles on it it will totally quiet down (I parked it right away to pull the motor and trans for rebuild on tranny and replacement/upgrade of enginge, its not done yet, waiting to be painted).

 

i'd suspect a professional mechanc could set it up corrctly, however if you took him your parts, or used parts i doubt they'd stand behind it. pull the cover and take a look, check back lash see what you can see. is it a clutch type posi? you might want to put some gm additive in it. sort of a long shot fix, but for a few bucks it'd be worth it.

 

If you has a shop put them in, they should stand by their work and make it right. If they don't I'd stop having work done there. Even if you supplied the parts, they should make it right. Although not for the average at home mechanic, setting up gears isn't exactly rocket science. Even used gears can be set up so they're quiet all the time.

 

IMO gears will never sound or perform right on a street driven car unless the rearend is broken in properly (Heat cycling). In this case however you couldn't even break it in. I think the shop should stand behind their work!

 

Pull your cover and inspect the pattern for the coast. It should be dead center between the toe and the heal of the tooth, my guess is its off to one side .The shop who set it up should fix it for you.