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Rear Axle noise


jimriviera

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My 67 Riviera with 3.07:1 positraction axle makes a growling noise. The sound changes with acceleration/deceleration. I am inclined to think it is either pinion bearings or ring/pinion wear. I wonder if it would be more economical (read-easier and or cheaper) to swap the entire axle assembly. Is the Electra or Wildcat the same? Any Ideas? Thanks<!-- google_ad_section_end -->

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Are you 100% sure the noise is coming from inside the differential? Is there any chance it could be an axle bearing or driveshaft carrier bearing? Before doing anything try to pinpoint the source which can be difficult sometimes.

If you raise and securely block the rear wheels off the ground and also the front wheels to prevent accidental forward and rearward movement, you can run the car in drive and try to pinpoint the noise. Or the safest method is to have a shop put it on a lift for you and check it.

The differential and pinion bearings in these were very robust and unless the differential was subject to abnormal use, its rather unlikley you would have a bearing problem......although certainly not impossible. The noise you describe does sound like bearing(s).

How many miles are on the car?

The Electra or Wildcat axle assembly is not the same.

As far as whether or not its better to replace the whole assembly or replace/repair a differential, I would lean towards repairing or replacing the existing. An exception would be if you had a 67 parts car with known good axle including bearings, seals and brake hardware. In that case it might be less expensive to swap complete assemblies assuming you can do it yourself. A rear axle assembly can be removed fairly easy but when contemplating this job you'll need to asses how rusty the bolts are that retain the track arms/bars. These can be a real SOB to remove on a car that has some rust issues. I tend to take the route that disturbs the least to prevent unexpected collateral damage which usually equates to more money spent and increased frustration.

If you don't have a parts car sitting around by the time you find and pay to go get or have an axle delivered, you will be further ahead fixing what you have.

Replacing the bearings on the differential and pinion would require paying someone with special tools. Few do-it-yourselfers have the ability, or desire to work on these but for those that specialize in it its no problem.

If you suspect the problem is definitely inside the differential make sure the oil looks OK and/or has been changed. Otherwise some dissassembly and inspection is needed inside the diff to determine the cause.

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OK! I jacked the rear end up, had my wife operate the accelerator pedal and I got under and listened. It is definitely coming from the pumpkin area. Sooo, I took the cover off and checked it out. The oil was somewhat foamy. I inspected the oil very closely, dragged a magnet through the bottom of the pumpkin. No metal flakes or chips at all. No sparkles in the oil. That has to be a good sign. I am a tool and die maker by trade and am familiar with fits and clearances--although this is foreign territory for me. I could see no visible wear on the ring teeth. I placed an indicator under the pinion collar and pushed upward with my hand. I was able to move it approximately .010". That seems like a lot of movement on the pinion bearing. What expert opinions are out there? Thanks.

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Jim,

If there is no metal that is floating around in the axle, that is a good sign. If the pinion yoke moves up and down .010", that is definately the cause of the noise.

I would suspect that someone replaced the pinion seal sometime in the past and didn't properly reinstall the pinion flange. As the car was driven, the pinion bearings worked loose and caused the noise and the up and down movement of the pinion.

If there is NO METAL at all in the differential, you probably have not damaged the bearings YET.

Here is how I would approach the repair. Jack the car up and support the rear axle housing with a jack stand in both ends of the differential. Remove the rear wheels and brake drums. Mark the relationship of the drive shaft to the pinion flange and remove the driveshaft. Using a inch pound dial type torque wrench, check the turning preload of the axle assembly. NOTE! This is not break-away torque but rotational torque! The total preload should be in the area of about 30 to 50 inch pounds. If it is lower than 30, which I would suspect, you can hold the pinion flange stationary and tighten the pinion flange nut up until you get the rotational torque in the 30 to 50 in. lbs. range. That should get the proper preload back on your pinion bearings and may solve the noise issue.

If there is ANY METAL in the rear axle fluid or housing, most likely your pinion bearings are toast. If that is the case, the bearings, seals and differential cover gasket are all available, the only part that I haven't looked for on this differential is the crush sleeve or collapsable spacer, but I have a couple of tricks for reusing the old one if needed.

Hope this helps,

Tim McCluskey

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Tim, Thanks for the reply. I read in the shop manual about the pre-load and how to adjust it. I didn't know that it would cause that kind of noise. But it makes sense. I will check it out. I really looked for any sign of metal in the oil but there was none. When I had trouble with my Astro van wheel bearings there was a lot of sparkles in the oil. Thanks again for the help.

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Tim, I adjusted the pinion preload. When it got to the point that there was some tension, I could feel a little roughness when I rotated the collar. On the test drive, the noise is definitely reduced---but not gone entirely. I still hear a little growl especially on deceleration. Based on the way the bearing feels when rotated by hand, I will probably feel better if I take the pinion shaft out and replace the bearings----For now it is much better. Thanks again for the help.

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Jim,

I suspected that might happen. You'll have to pull the differential case out of the housing to get the pinion out, and there are some other measurement you'll have to make as it goes back together. You set pinion bearing preload, backlash and then side bearing preload. Check the pattern and you should be good to go!

Tim

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