Input for C3 Differential noise

[Tim S.]

I had a noise which I and a coulpe others felt a had a set of gears and / or pinion bearings that were bad. From 50 MPH on up, I had a growl as well as a vibration that I could make change with acceleration, coast, deceleration, etc. So yesterday, I pulled the diff out to send it to the rebuilder. While pulling this apart, I noticed I have a tight half shaft joint. Have any of you experienced a joint to cause the symptoms described? I have not pulled the cover off of the diff yet but I must say, laying on the bench, I cannot find anything with the diff that alarmed me. By the way, this is a car I just purchased so I have no credible history. The previous owner says he never had any noise.

Thanks,

Tim

[Edward J.]

Re: Input for C3 Differential noise

Tim, if it were me I would replace the u-joint, when they seize like that , there would be a vibration, and some noise as the needle bearings do make nosie without any lubrication, sending out your rear axle for rebuilt is costly. generally bearings are not a certain mph problem, they start from 5--10mph and contiune more notiable the faster you go.

[Duke W.]

Re: Input for C3 Differential noise

Spalled bearings usually emit a growl, moan, or scrapping noise that is fairly constant with speed and not torque sensitive.

Ring and pinion noise usually peaks at a certain speed and is torque sensitive.

Try turning the pinion nut with a speed handle and listen for noise. You shouldn't hear much of anything if the bearings are okay.

Disassembling the axle is fairly simple, and with it apart, you can inspect the bearings. Prior to disassembly, measure side yoke end play. It's also a good idea to measure total drag torque, and if it's less than the pinion bearing preload spec the pinion bearings might be bad. Proceed with removing the cover and measure ring and pinion backlash and tooth contact pattern.

The next step is to remove the diff. case, and then check pinion bearing preload prior to removing the pinion nut. Make sure you mark the pinion nut position and install it to the same point, but it's best to reininstall it to the appropriate preload spec.

Once apart you can inspect everything. If all is well put it back together. If bearings need to be replaced you'll need a press and suitable race removers/installers, and you can make a decision whether you want to proceed with the overhaul or send it out.

The procedure is in any Corvette COM, and there was an article in the Corvette Restorer a few years ago with additional information on overhauling the axle.

Duke

[Tim S.]

Re: Input for C3 Differential noise

While watching the race today (Talladega). I popped the cover off of the diff and fooled around a little bit. The gears look real good. No galling, chipping or pitting. In turning the pinion yoke, it was smooth and quiet. I am a little dumbfounded. Can that u-joint cause that much of a problem?
Also, the fluid I drained and the remains of what was in the bottom of the case was more than permissable in my opinon.

[Gary R.]

Re: Input for C3 Differential noise

Duke covered a lot. I have several threads on rebuilding/checking diff's. I would look at them. I have one on replacing joints as well.

shaft thread

http://www.digitalcorvettes.com/forums/showthread.php?t=76752

Diff threads

http://www.digitalcorvettes.com/forums/showthread.php?t=77316

http://www.digitalcorvettes.com/forums/showthread.php?t=76719

http://www.digitalcorvettes.com/forums/showthread.php?t=77713

http://www.digitalcorvettes.com/forums/showthread.php?t=77377

There's a few more but these cover just about everything from a stock rebuild to 1000hp build.

[Duke W.]

Re: Input for C3 Differential noise

While watching the race today (Talladega). I popped the cover off of the diff and fooled around a little bit. The gears look real good. No galling, chipping or pitting. In turning the pinion yoke, it was smooth and quiet. I am a little dumbfounded. Can that u-joint cause that much of a problem?
Also, the fluid I drained and the remains of what was in the bottom of the case was more than permissable in my opinon.

Geez, I didn't think that race would EVER end!!!

The U-joint could produce the symtoms you reported. Bad half shaft joints can provide a range of symptoms from virtually nothing to really weird.

What about yoke end play and R&P backlash?

Also clean out any sludge at the bottom of the carrier.

If the axle checks don't indicate a problem, replace the U-joint and check all the others - making sure they move freely, and you're probably okay putting the axle back in without further work.

Duke

[Tim S.]

Re: Input for C3 Differential noise

the endplay / backlash is similar to known good diff's. It has me spoofed. I am going to have someone qualified look at it before I go through the effort of reinstalling it to only find out it needs to come out again.

Thanks,

Tim