07redMustang

I just got my 3.73 gears installed by a local shop. He rebuilt transmissions for 15 years at ford before working at this place. I gave him the gears an install kit and a new notched crosspin. He had the car for the whole day because he said he wanted to do it just right. I've taken it easy on the gears but I did floor it once getting on the highway (I couldn't help it I had to pass this guy who wouldn't let me get over). Anyways the gears are fine when crusing 55mph or under but after that I hear a humming type noise coming from the rear end. I wouldn't call it a whine though more like a hum. I only hear it when going over 55mph and I have my foot on the gas. The gears haven't went through the 500 mile break in yet either. Is this a normal break in noise or should I take it back to the shop?

Thanks

Sancho805

if its a low humm, it may fade out some. if its loud, then you can expect the noise to stay. what brand are the gears?

mustangman02232

did you do the three heat cylces before you got on it? how loud is it?

07redMustang

What's the three heat cycle? The noise isn't too loud but it is noticeable. The gears are motive.

addison85

Looks like symptoms of gear whine.

jdphillips73

you should drive the car for like 15 miles, then let the gears cool off completely, then repeat 2 more times.

it sounds like the backlash or pinion depth is not set right. thats the only reason gears make noise, that is, when something isn't set right.

Sancho805

or occasionally aftermarket gears that are not cut to EXACT oem specifications.

07redMustang

I've drove the car quite a bit and the humming has gone down a lot. I can still hear it from time to time but if I'm not trying to listen for it then I don't notice it anymore.

Sancho805

sounds like they just needed to be broken in and that they've now developed the wear pattern. whatever noise they make at this point should be what sticks. how are you enjoying that takeoff acceleration with your new gears? [8D]