Rear end whine

waynetd · March 1, 2005

I have a 98 ext-cab Z71 with 77,000 miles on it. Friday I took the truck in to a driveline shop to get my rear diff repaired because of a loud whine in it. They listened to it and determined my pinion bearings were going bad. They replaced the pinion and carrier bearings. I have drove the truck for the past few days and I can still hear a whine. At certain RPMs, the whine is louder now than it was before they repaired it. I'm taking it back to them tomorrow after work.

What could be wrong? Did they not install the gears back in correctly? After spending $425, I'm pretty irritated about this.

Has anyone else here had rear diff problems on their old body style 1/2 tons? This shop says that they do tons of these 10 bolt rear ends due to the fact that the pinion bearings are too small. I hope they get this figured out.

Wayne

Bgdsub72 · March 1, 2005

add some GM limited slip additive, that usually solves the problem...

waynetd · March 1, 2005

They added limited slip additive to the new fluid so its not that. I took it back today and we drove it and they put it on the lift. The guy thinks its a pinion bearing again. He said one of the new bearings probably had a flat spot on it. I know it was louder than the ones I had replaced. They said they should have it fixed tomorrow so I'm keeping my fingers crossed.

Wayne

Taaaaaaahoe? · March 2, 2005

Rear end whine, What could be wrong?

Take the wife or kids out of the back, that should do it

MIKE

GM-Tech · March 2, 2005

Replacing those bearings requires precise setup of the gears. Sometimes with a bearing that has been bad for some time, even replacing the bearings and setting up the gears correctly will not eliminate the whine once the ring and pinion has developed a bad pattern due to the bearing failure. When we have failed bearings in a rear end, we ALWAYS quote the ring and pinion as part of the repair, otherwise I know we're going to live with it.

It is possible to replace bearings, set up the gears and have a quiet ring and pinion, but that's always a gamble and you won't know until you drive it after the repair.

Ring and pinion noises are typically loudest around 45-50 mph. And usually, they will make noise only on accel, only on decel or only on float, and only one of those. Is this what you have?

TrumanDrive · March 2, 2005

GM-Tech,

you mention that noise from a worn ring and pinion is worst at 45-50 mph. can this also cause a driveline vibration at a specific speed?

thanks

waynetd · March 2, 2005

GM-tech,

That is pretty much my symptoms. My noise is usually between 40-45 mph and happens mostly on decel. I just talked to the shop and they said they found a flat spot on one of the bearings. I asked about the ring and pinion and they said it looked fine. I've always taken very good care of this truck. The rearend fluid had been changed three times at the time of the repair with Mobil 1 diff fluid being used for about 57,000 miles of the 77,000 miles on the truck. I don't know if I trust this rearend anymore with the bearings going out so soon. Thanks for the info.

GM-Tech · March 2, 2005

A ring and pinion can make the most awful howling noise at 45 and if you looked at the gears, you probably wouldn't see anything significant. If you put a quiet gearset and a noisy gearset side by side, depending on a number of factors, it could be difficult to tell them apart.

Either they didn't properly set up the gears, which takes a special touch and some experience, or yours is beyond any setting that will make them quiet.

The good news, if you can call it that, is that a vehicle with just a gear noise issue can go for thousands upon thousands of miles with no other problems other than the annoying noise.

And to answer the other question above yours... no, I don't see a worn ring and pinion causing a driveline vibration. Maybe if the pinion was flopping around in there like a fish out of water, but generally, they can be in pretty bad shape and will just make noise but not impart a driveline vibration.

silverado3500 · March 3, 2005

GM-Tech hit the nail on the head, The backlash might not be set quite right, or the gearset is worn beyond repair (at least on the sound issue).

budhayes3 · March 3, 2005

A third here in agreement with what GM-Tech and silverado3500 said, especially since the noise is more prominent on decel when the mesh between the ring and pinion shifts. If the bearing was bad, the noise should be there all of the time and increase with speed.

waynetd · March 3, 2005

Well, I got the truck back from the shop and it seems that they fixed it. I don't hear the noises that I heard before. I will drive it a few days before I deem it completly fixed. A different guy than before worked on my truck today. You guys who said backlash were correct. The guy today said that the backlash was set too tight and that one of the spacers was actually broken. He also said that a couple of the new bearings were bad but I don't know if they got damaged from the too tight backlash or they were that way from the beginning. They put a new bearing kit in it so hopefully I won't have any more problems. I looked at the gears while they still had the cover off and they didn't looked damaged at all. The guy who worked on it said that they were fine.

I was surprised that the mechanic today actually admitted that someone from the shop had screwed up. He said that the guy probably wouldn't admit that he had done something wrong. I hope they either teach him how to do this stuff right or get rid of him. Thanks for all of the information.

Wayne

etex211 · March 10, 2005

I'd be pissed at the shop. Like GM tech said, it takes a special touch and a lot of experience to set up gears properly. It sounds like the shop let a newbie loose on your gears the first time and I would not be happy about that.

waynetd · March 12, 2005

Well, I have driven the truck for over a week now and I still have a very slight noise on deceleration. Its nowhere like it was originally or after they fixed it the first time. They have a 90 day warrenty on their work so I'm going to drive it more to see if it gets worse. Its really not that noticible unless you listen for it. I can live with it if it doesn't get worse. I can't really afford to have new gears installed right now so hopefully this repair will hold up.

I was a little pissed at first but they admitted that there was a screwup and got right on it getting it fixed so I will give them the benefit of the doubt this time. I doubt the owner was real happy with the guy since they had to buy another $100 bearing kit and then take the time to tear everything back down and put it all back together again. I don't know how much experience the guy has who originally worked on my truck, but it I ever have anything else done by them, I will ask that he doesn't work on my truck again.

Wayne

waynetd · March 25, 2005

Well, its been about 600 miles since the repair and the truck is still not fixed. The noise has gotten progressively worse. I put the truck up on jackstands and put it in drive and revved up the engine. On deceleration, you could hear the rear end start whining pretty loudly. My Anti-lock brake light in the dash also came on and stayed on until I shut the truck off. It hasn't came on since. I hope thats not going out. I am taking the truck back to the shop on Monday but I really don't know what to do.

Does anyone know what I should do at this point?

Wayne

GM-Tech · March 25, 2005

Well, its been about 600 miles since the repair and the truck is still not fixed. The noise has gotten progressively worse. I put the truck up on jackstands and put it in drive and revved up the engine. On deceleration, you could hear the rear end start whining pretty loudly. My Anti-lock brake light in the dash also came on and stayed on until I shut the truck off. It hasn't came on since. I hope thats not going out. I am taking the truck back to the shop on Monday but I really don't know what to do.

Forget the ABS light. You caused that. The ABS saw rear wheel speed but no front wheel speed and said, "hey, something's wrong." It didn't know you weren't driving down the road.

Don't know about the noise. Testing it jacked up is not a good test. What's it like driving? If you have to really listen for the noise, it may not be out of the ordinary. A rule of thumb from GM is that if you can hear it with the a/c on medium blower speed, it's not normal.