Help... Noisy 12 bolt

[carbondaddy]

First a little history. 69 Camaro 12 bolt posi. It had 3.90 gears which were too much so I had a shop install 3.07's until I can afford a 5 or 6 speed. While it was apart, we found that it had suffered some trauma in the past. The carrier had pretty deep gashes from what looks like the pinion gear. He measured the runout on the ring gear and it was within 1 thou, so he thought it was OK and finished up with the change over. Ever since, the rear end is very noisy under light acceleration and steady cruising. I've had it back in the same shop 3 times and had another mechanic look at it. Each time they say it is within specs (I don't know too much #'s). Any ideas? The carrier hooped, the replacement gear set not good? I didn't notice the 3.90's being noisy, but the rest of the car was very loud. Maybe it's just time to spring for the overdrive tranny and put the 3.90's make in.

[big gear head]

What brand of gears did you put in it? Were they new or used gears? How was the pinion depth set? What did the contact pattern look like?

I used Richmond 3.08 gears a few years ago and every set that I got was machined so bad that no matter what I did to them they made a lot of noise. This was a bad batch of gears. I sent several sets back and finally got a set of US Gear 3.08s and they were fine. The 3.08 ratio is not very much in demand so they don't make very many of them. Whoever sets up the machine to cut the gears may not have done a good job.

[carbondaddy]

They were Richmond, new, and that's about all I know for sure. I wasn't there when the work was done. I may have to take it apart and check it out myself.

[H2Ogbodies]

What do mean as in "within spec"? If the housing where the pinion resides had deep gashes, that means at some point in its past, the shims were ground down to dust and the pinion hit the housing from the inside or something let loose at one time. See if you have trouble pulling an axle out of either side....I would suspect the housing to be a little racked/twisted. It it is, this would show up on the wear pattern of the ring/pinion BUT-you would need to do only one revolution, then pull it apart to inspect it.

[CarlC]

Freddie, in general, who makes a good set of quiet gears? My 10 year old Richmond 3:73:1 / 12-bolt have some whine to them and I'm considering swapping them out this winter if the contact pattern looks OK.

[carbondaddy]

What do mean as in "within spec"? If the housing where the pinion resides had deep gashes, that means at some point in its past, the shims were ground down to dust and the pinion hit the housing from the inside or something let loose at one time. See if you have trouble pulling an axle out of either side....I would suspect the housing to be a little racked/twisted. It it is, this would show up on the wear pattern of the ring/pinion BUT-you would need to do only one revolution, then pull it apart to inspect it.

I know the carrier has gashes, not sure of the housing. The axles pull out easy. You say one revolution... of the pinion or the ring gear? What would I look for in the wear pattern?

[big gear head]

Most of the Yukon gears that I have installed have been quiet. Most of the US Gear sets have been quiet. Most of the Richmond gears ahve been quiet. Sometimes you get a bad gear and it could have anybody's name on the box. Motive made some gears in Korea and as far as I know they were all junk, but the gears they made in Italy were good.