Rear end whine from 40 to 60 MPH

[dalekerr]

Guys I need some help please. I bought a used 67 12 bolt for my camaro and had it installed with new gears, bearings and one new axle. The rear end has had a whine between 40  and 60 mph. Youy can play with the throttle and make the whine come and go.

I've since had the gears and bearings repalced twice and a new posi unit installed. Three different mechanics replaced the gears and bearings, they all had years of experince on rear end gears.

What else can be causing the noise? Maybe a bad axle? 

I plan on taking this car on a road trip on Route 66 and would love to hear the radio instead of the rear end whine.

Suggestions please, short of replacing the whole rear end. The transmission has been rebuilt recently also.

Thanks in advance

Dale Kerr

[WorkinProgress]

The only experience I had was 30 plus years ago, when we put Richmond Gears in the housing. I think the original instructions said you would hear a whine.

GM gears do not whine. Think they have better tolerances.

What make gears did you use and were they a matched pair from day one?

                                                              - Warren

[169INDY]

My Yukon Gears Whine also (?) Guessing  if that brand matches the Posters. Even Similar RPM (MPH) range.
Mine is nominal and not severe. 12 bolt 3:42 w/ Eaton Posi.

[dalekerr]

They were all new gears, first set was US gears made in US  then two sets of yukon firts was 3.42 then tried 3.31.
I bought a set of gm 3.31 used gears that looked good, but got talked out of using them. I think UI should have insisted on using them.

[Mike S]

My 67 convertible still has the original GM 'QK' 3:31 posi rear with 61,000 miles and there is a faint but audible whine around the same speeds mentioned above. It only occurs when driving and is gone when coasting. When I was restoring the car and had the rear out and the cover off I could see the gear contact pattern appeared in the proper area of the teeth so I figured the pinion depth was correct and ring spacing was fine.

Mike

[cook_dw]

You need to look at the gear pattern on the drive and coast side of the ring gear.  Sounds to me like the pinion depth wasn't set correctly but that is a guess at this point.  I personally hate Richmond gears.  Yukon and GM is what I have had the best luck installing.

[Mike S]

 The top example is what I have seen on my 67.

Mike

[dalekerr]

Well today I pulled the diff cover and checked the pattern. It looked good so I changed the oil to Lucas 85/140 conventional oil, added the special clutch lubricant and drove the car. The whine is not as bad as before. I am going to next pull the carpet and add insullation. I think I can live with the minor whine then. It is most noticable at 55mph. I guess I will drive 60 and above instead!

Note the last mechanic put in 75/90 synthetic oil, my research shows that synthetic oils let the gears whine louder. I believe this to be true, since last time after the gears were changed I went from conventional oil to synthetic and the whine got louder.

Thanks for the helpfull posts.

[usa1ti]

Read over this setup article. https://www.racingjunk.com/news/how-to-set-up-your-rear-gear-correctly/.
This is really close to how I set up most of rearends in my super gas / top sportsman car. Usually if you have a whine that comes and goes its a backlash issue. I use Royal Purple synthetic in all race and street cars. The new gear must be broken in right or it will never be dead quiet. None of those gears below about a 5.57 / 5.86 should make any noise if set up and broken in correctly. Above that ratio may whine a little.

[Kelley W King]

There was a recent article in Muscle Machine mag which was about 9 inch rears but it said the aftermarket was using a different grinding process than the OEM stuff. Said they are noisier that factory stuff. I used Richmond in my GTO but between the M22 and the flowmasters I can,t hear the rear gears.

[crossboss]

Boys,
Richmond ring and pinion gears have always had a reputation for being soft. As a result, they whine more than OEM and better quality sets. Also, as mentioned it CAN be caused by improper set up, and using synthetic gear oil. I personally only use good 'ol dinosaur 75-140W. Lastly, IF using a posi, make sure you add the friction modifier.