rear axle gear whine!!

I am hoping that someone can help me with a gear whine issue. I have a 69 firebird with a newly broken in sbc406, 10:1 comp, ported 461 feulie heads, xe274h cam, air gap intake, etc. Tranny is a freshly rebuilt super T-10 (2:88 first gear) Rear is a Mopar 8 3/4" (489 casting) with a 3.91 and a posi.
I took the car out late last night to a very remote straight stretch of open road for some personal test and tune practice. I've gotten used to the th400 but I wanted some practice with the T-10 running it hard and experimenting with luanching techniques running BFG radial 275-60-15TA's(not the drag radials, the street tires) I gave it around 15 hard runs through 3rd gear in three sessions. Everything went well. After I was done I pulled over and checked the basics again.
On the way home I noticed what sure sounds like a gear whine in the rear axle only when I let off the gas. It will do it in a 4 gears. Its not a brutal sound or anything. It's an even consistant gear whine sound starting as soon as I let off the gas and stays until I give it just the slightest bit of gas again. Other than the noise, it runs great. No change at all. No gear crunching noises, no popping, nothing intermittent. I took it for a short ride this morning, same thing.
I was planning to bring the car over to ATCO Raceway (NJ) tomorrow for its first time out with the new motor tranny combo. I have a feeling that is not going to be a good idea. Any ideas guys?

Thanks,

George

Sounds like with your practice launches that you have pushed in the pinion crush sleave causing clearance to open up between the pinion and crown wheel. When you let off the gas the clearance opens up giving you the whine. Giving the gas drives the pinion back into the crownwheel therefor closing up the gap. What you need to cure this is a solid sleeve to replace the stock crush sleeve. Or a stronger diff (ford 9 inch) If you are really going to get on and keep on consistently with the power.

Thanks for the thoughts...it sounds logical. The gears have less than 4000 miles on them so they shouldn't be worn out or anything. It didn't seem as though I was able to put any major loads on the rear but I guess I managed to. Ooops! My "testing" mostly consisted of carefully letting into it off the line tying to get the best launch with minimal tire spin. Quite honestly I'm having a hard time getting those old school BFG radial ta's (275-60-15) to hook up much at all. At the track with the old motor/trans, breaking low 1.9s in the 60ft. was a challenge. I have tracked down a speed shop guy I know who is known for his work on rears for race cars. He should be able to get to it by the end of the week. Hopefully it won't be major surgery. I've got a nice 10bolt rear in the garage though I'll asume it won't be necessary.

Hey gs........there is some guy trying to find you on the "Offenhauser dual quad" thread, but he can't seem to find you.:confused: :confused: You might want to hop onto that thread and tell him you haven't left the country.:D :D

I usually get a fee for this kind of matchmaking.


Don

Hey Itoldyouso, I got a hold of him. Thanx a lot!!

Kenton

I take all major credit cards.:D :D :D :D :D


Glad you guys finally hooked up.


Don

The fainter whines like that from a differential are almost always bearing related. Whether it be improper preload causing parts to move around and messing with clearances as stated earlier or severely worn bearings.