65 Coupe Rear End Howl

[Bob Babcock]

I just finished a body off restoration of a 65 coupe. It is a 300hp powerglide factory a/c car. My mechanic rebuilt the rear end using new Richmond gears, but it now has a VERY loud howl during accelleration and decelleration. It makes noise even during cruising, but not as bad as accelleration and decelleration. It is getting much better, but it is still too darn noisy.

The Richmond gear distributor said I can put another gear set in and it will also be noisy. He further stated that GM quit making replacements in 1972 and Richmond gears are always noisy and Richmond is the only source for aftermarket gear sets. I believe the current gear set is 336:1. The distributor said that changing the ratio will not cure the problem.

Any ideas?

[Wayne W.]

Re: 65 Coupe Rear End Howl

Use your old ones. If Richmond cant build a quiet set, they should get into another business. There is no reason for a 3:36 to make any noise.

[Wayne W.]

Re: 65 Coupe Rear End Howl

Use your old ones. If Richmond cant build a quiet set, they should get into another business. There is no reason for a 3:36 to make any noise.

[Joe L.]

Re: 65 Coupe Rear End Howl

Bob------

Richmond-manufactured replacement gear-sets for 63-79 Corvette differentials are noisier than stock GM. It shouldn't be a massive difference, though. The GM gear sets were the quietest, though, and that's why they're very desirable. Your distributor is correct in that the GM gearsets are discontinued and out of production. It didn't happen in 1972, though. After all, they were still using these gearsets in PRODUCTION through 1979 and they were produced for SERVICE well after that.

Your distributor is incorrect regarding the fact that Richmond is the only manufacturer for the gearsets. US Gear, and I believe one other manufacturer, make them. The US gear product is a lot more difficult to find in the marketplace since they do not sell direct and the do a production run only when a distributor "steps up to the plate" and orders a complete production run. Tom's Differentials of Paramount, CA is such a distributor and the US Gear-manufactured gearsets are available from them. Dial-them-up at www.tomsdifferentials.com

I prefer the US Gear-manufactured gearsets for exactly the reason that you MAY be having trouble with the Richmond gearset-----the US Gear product is more like the GM gears with respect to quietness of operation.

One more thing: the noise which you are experiencing is not necessarily due to the gearset, itself. The biggest factor with respect to gear howl/noise relates to how well the gears were set-up by the person that did the work. So, the "unacceptable" part of the noise that you're experiencing may not be due to the gears, at all.

[Joe L.]

Re: 65 Coupe Rear End Howl

Bob------

Richmond-manufactured replacement gear-sets for 63-79 Corvette differentials are noisier than stock GM. It shouldn't be a massive difference, though. The GM gear sets were the quietest, though, and that's why they're very desirable. Your distributor is correct in that the GM gearsets are discontinued and out of production. It didn't happen in 1972, though. After all, they were still using these gearsets in PRODUCTION through 1979 and they were produced for SERVICE well after that.

Your distributor is incorrect regarding the fact that Richmond is the only manufacturer for the gearsets. US Gear, and I believe one other manufacturer, make them. The US gear product is a lot more difficult to find in the marketplace since they do not sell direct and the do a production run only when a distributor "steps up to the plate" and orders a complete production run. Tom's Differentials of Paramount, CA is such a distributor and the US Gear-manufactured gearsets are available from them. Dial-them-up at www.tomsdifferentials.com

I prefer the US Gear-manufactured gearsets for exactly the reason that you MAY be having trouble with the Richmond gearset-----the US Gear product is more like the GM gears with respect to quietness of operation.

One more thing: the noise which you are experiencing is not necessarily due to the gearset, itself. The biggest factor with respect to gear howl/noise relates to how well the gears were set-up by the person that did the work. So, the "unacceptable" part of the noise that you're experiencing may not be due to the gears, at all.

[Bob Babcock]

Re: 65 Coupe Rear End Howl

Thanks Joe,that is great information. I understand there are indexing and preload issues, etc. and they make a big difference. That may be a good part of my problem. Of course, the mechanic would like me to believe it is all Richmond's problem, hee hee. I will contact Tom's Differentials. Thanks a bunch!

[Bob Babcock]

Re: 65 Coupe Rear End Howl

Thanks Joe,that is great information. I understand there are indexing and preload issues, etc. and they make a big difference. That may be a good part of my problem. Of course, the mechanic would like me to believe it is all Richmond's problem, hee hee. I will contact Tom's Differentials. Thanks a bunch!

[Craig S.]

Re: 65 Coupe Rear End Howl

Bob - as always, Joe's points are right on the money. Also, a premier Corvette rear end rebuilder, that teaches classes at Bloomington, is Charlie Smith at Charlies Performance in Champaign/Urbana IL. He is a great guy, and I bet he may have some used GM parts on hand. He also makes the same point as Joe - use US Gear for aftermarket, not Richmond. There are also some tricks about tuning the mating pattern for quietness, and others for power such as drag racing. Good luck!...Craig

[Craig S.]

Re: 65 Coupe Rear End Howl

Bob - as always, Joe's points are right on the money. Also, a premier Corvette rear end rebuilder, that teaches classes at Bloomington, is Charlie Smith at Charlies Performance in Champaign/Urbana IL. He is a great guy, and I bet he may have some used GM parts on hand. He also makes the same point as Joe - use US Gear for aftermarket, not Richmond. There are also some tricks about tuning the mating pattern for quietness, and others for power such as drag racing. Good luck!...Craig

[Bob Babcock #33116]

Re: 65 Coupe Rear End Howl

Thanks Craig. Yes, Joe is always on the mark....and Duke and Rev and Jack and Clem....etc. Lots of knowledge here. The discussion board is well worth the price of admission to NCRS.

Interesting you should mention drag racer vs. restorer. My mechanic owns a very competitive pro comp drag racing car that I will be watching this afternoon, hee hee. I'll bet it is an issue of indexing or preloading.... or another installation issue. He is going to put in a new set of gears next week. He is convinced that the 3:36 (3:30?) gears are inherently loud. He is going to put in the next lower ratio. Heck, it is his dime and it was a bit tall geared anyway. He is a bit stubborn and won't warranty U.S. Gear products. He claims they are made in India, hee hee. Oh well, I could always take up drag racing.

[Bob Babcock #33116]

Re: 65 Coupe Rear End Howl

Thanks Craig. Yes, Joe is always on the mark....and Duke and Rev and Jack and Clem....etc. Lots of knowledge here. The discussion board is well worth the price of admission to NCRS.

Interesting you should mention drag racer vs. restorer. My mechanic owns a very competitive pro comp drag racing car that I will be watching this afternoon, hee hee. I'll bet it is an issue of indexing or preloading.... or another installation issue. He is going to put in a new set of gears next week. He is convinced that the 3:36 (3:30?) gears are inherently loud. He is going to put in the next lower ratio. Heck, it is his dime and it was a bit tall geared anyway. He is a bit stubborn and won't warranty U.S. Gear products. He claims they are made in India, hee hee. Oh well, I could always take up drag racing.

[Craig S.]

Re: 65 Coupe Rear End Howl

Best of luck...I have heard that aftermarket 3.55 ratios are a bear to keep quiet from Charlie, I don't know if US Gear is made in India or not, nor do I know if Richmond is made in US or not, but I haven't heard anything about 3.36 gears causing a howling if set up properly. Charlie pointed out that setting the pinion deeper into the ring gives a better drag racing mating pattern, at the expense of noise...whereas a typical centered pattern is quieter and better for the norm. It is important that the pattern is not running off the edge of the ring gear in any direction, to prevent excess load on the edge of the tooth, also cusing excessive noise. Also, the bearly preloads, posi pack setup and stub axle end play etc are all very important. Good luck with your setup!....Craig

[Craig S.]

Re: 65 Coupe Rear End Howl

Best of luck...I have heard that aftermarket 3.55 ratios are a bear to keep quiet from Charlie, I don't know if US Gear is made in India or not, nor do I know if Richmond is made in US or not, but I haven't heard anything about 3.36 gears causing a howling if set up properly. Charlie pointed out that setting the pinion deeper into the ring gives a better drag racing mating pattern, at the expense of noise...whereas a typical centered pattern is quieter and better for the norm. It is important that the pattern is not running off the edge of the ring gear in any direction, to prevent excess load on the edge of the tooth, also cusing excessive noise. Also, the bearly preloads, posi pack setup and stub axle end play etc are all very important. Good luck with your setup!....Craig