Whining Noise When Letting Off The Gas

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BubbaCuda

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I need some help with this one. When I let off the gas I get a whining noise that sounds like its coming fom the rear end. The sound is not there when i am on the gas. My old rear end was a 7 1/4.This is the changes to the rear. i will list everthing to help with the troubleshooting.

- rebuildt 8 1/4 321 with suregrip new seals and bearings
- 11 x 2 inch drum brakes
- shortened drive shaft 1.6 inches
- 17 inch wheels
- 5 pack hd leaf springs
- Firm feel sway bar
- firm feel front hanger using top position to lower car 1.5 inches

Thanks for the help
 
yes. I just got the car back on the road last night. i noticed it right away today while i was driving to get it aligned.
 
Thanks for the reply
I will call rearend specialist in the morning....i hope its an easy fix...i really wanted to cruise around this weekend after the car being down for the last month.
 
hkeller said:
Thanks for the reply
I will call rearend specialist in the morning....i hope its an easy fix...i really wanted to cruise around this weekend after the car being down for the last month.
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If your specialist know his stuff the rear end cover comes off and he'll set up a dial indicator on one of the teeth and know if the backlash is correct or not real quick.

Terry
 
hkeller said:
Its about 15 miles
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I'd say let your specialist make that call cuss if anything happens it'll be warranty. !5 miles is a bit long especially if the rear is set up to tight and she'll get hot.

If I was a betting man I'd say that he didn't have enough preload on the carrier bearings and when the backlash was set originally in the shop it's opened up slightly now that you're running it. But that's only a guess until it all gets rechecked. Good luck and stick to your guns. Opps don't take that gun part literally, I've heard some stories about west coast drivers. LOL:toothy6:

Terry
 
It could also be the outer (small) pinion bearing. This bearing is loaded when you are coasting causing it to make noise. But being the setup is new it is probably in the ring and pinion. Some aftermarket gear sets can have noise even if they are set up correctly, I have seen (or should I say hear) it before.


Chuck
 
I called Rearend Specialist today and they had me bring the car in for a test drive. Immediatly the mechanic said wow thats loud and at all speeds.. They took the cover off and checked it out and found nothing wrong with the backlash. The gears had a perfect pattern at there contact point. he then determined that the Sierra brand 321 gears they sold me do to their cut was extra loud and was amplified do to the fact it was a fastback car..They did not want to put another set of Sierra brand gears in my car thinking they would be just as loud. After searching his stock of gears he found a set of 373 OEM gears that he would install if I was not concerned about freeway RPM..I had called while they were installing the gears the first time asking if they could install 355 thinking i went to conservative with the 321..But it was to late because they had already finished the rear end. Anyways i was happy with going to 373. They installed the new gears while i waited. We went for a test drive No more gear noise.. Just the sound of the flowmasters.. I was very impressed on how Rearend specialist had taken care of the problem. They could have easily of tried to weasle out of fixing my rearend .....Thanks again for all the advice...
 
I've heard of noisey gears when they're new but that's just bizzare. Anyway it sounds like they did right by you and if you like the ratio that's even better.
Who knows the shop that did the work might even get more from readers of this thread in your area, that's the main benefit of good customer service.
Terry
 
Now you've got to find a gear for your trans to make the speedo read correctly, & you'll be all set. Might take a bit of searching, though.
 
I'm not sure which type you have. I know the manual trans stuff changed in 1966. Not sure about the auto trans stuff, but I know the 66 & up manual type is the same as the later auto trans stuff, was in use for a long time & is easily available. You can find charts on line that will tell you how to figure what gear you need if you use the later style.

Assuming your speedo read correctly before the gear change, here's an example of how to do the math.

Old gear ratio =3.23
New gear ratio = 3.91

3.91/3.23 = 1.21
Now, count the number of teeth on your old speedo drive gear. I don't know what your is so I'll use 30 as an example.

1.21 x 30 teeth = 36.3, so you need a new speedo drive gear with 36 teeth. If you change to a taller or shorter tire, you use the math to determine the % difference in diameter & then use that percentage to determine the new gear tooth count.

Just remember; A numerically higher gear ratio in the axle or a smaller tire diameter will result in the need for a higher tooth count on the speedo drive gear. This is because the drivetrain has to turn faster to go the same speed, so the speedo has to be slowed accordingly.
 
Calculator works great.

SOcA30.jpg
 
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