rstarkie

1999 Z28 6 speed 3.42 10 bolt 53K

I am unable to determine if the noise I am hearing is axle bearings or the rear end. Relatively low miles on this car and it is not raced or thrashed.

I was alarmed that the differential lube was low. It was 7/8" below the full level. The pinion seal is leaking.

The noise is most pronounced about 30 mph and seems to be independent of load on the drive line. Accelerating or downshifting does not seem to change the sound. Out of gear coasting the sound remains the same.

I have the rear on jackstands with the rotors off and with it in neutral I can easily spin the axles by gripping one of the wheel studs. I am unable to isolate the sound.

Other than removing the axles and replacing the wheel bearings and seeing if that fixes it is there any way to determine what is at fault??

In your experience is the 7/8" below full level a rearend buster??

Thanks for any help.

Randy

massls1guy

iTrader: (9)

I would pull the axles out, check the bearings and the surface of the axles that the bearings ride on. That's pretty easy to do, just a little more work than changing the rear axle fluid. In my case one axle had a deep groove in it, no question there. Fyi, Autozone rents the alxe bearing puller for free.

For the pinion seal I would check the vent on the passenger side of the pumpkin near the top. If that gets plugged it can cause pressure to build up and then the pinion seal can leak. If it's dripping I would fix the leak. If it's a slow seep I would just check the level regularly.

If you fix up the axle bearings (and new seals) and it still makes a little noise I might just run that too. Not if it's an evil metal on metal noise, but I would run it with a bit of a whine.

jcbache

I've got the same noise. Any update on what you found out? My car has 96k on it ( it's a 99 Z28 6 speed )and I just bought it from some nerdy guy who I seriously doubt thrashed it. Noise was there when I got it. I was wonderind if it might be corroded-up emergency brake parts. I've put new slotted /cross-drilled rotors and new pads all the way around when I first got the car 'coz it had been sitting for a couple years.

FirstYrLS1Z

iTrader: (4)

If the 'noise' is in sync/same as tire rotation(1 'noise' per tire rotation),it points to axle bearing and or carrier bearing. If the noise is 3-4 occurences/times tire rotation,it points to pinion bearing(s).
7/8" below full should not be a 'rearend buster',unless the lube is 'burnt',but it would take a lot lower level to cause that.
If a bearing is failing,all the disinegration of that bearing is mixing in the fluid and affecting the other components. The attached magnet on the cover inside surface is there to remove and hold any iron/steel contaminating particles.

Spartan7

iTrader: (7)

Not necessarily. Mine started whining all the time, during coast and under load. Turned out to be a fried pinion bearing.

Do what was already posted above, and pull the axles to check them out. If they look good, then it's probably time for a rebuild.

blitzace12

iTrader: (1)

I had a very constant grind that got a little louder as i speed up. It also got softer and louder as i turned. It turned out to be a very bad carrier bearing and a bad pinion bearing. If you have a bad bearing you should see some metal on that magnet. Wheel bearings will get softer or louder depending on what way you turn. Go out on the highway and make some turns on some off ramps and see if it gets better or worse.

SparkyJJO

iTrader: (11)

Not always. I had a bad axle bearing on the driver side (and a shot axle surface, needed a new axle) and it didn't change when I turned. So much quieter once I replaced that. I did both sides while I was in there, figured why not before the passenger one went and took that axle too.

You might as well check the axle bearings first, since you'd have to pull the axles to change the carrier bearings anyway. And the axles are the easier things to get to.

The Mighty Texan

iTrader: (4)

I think i may have something the same or different, i would decribe it as more of a "whine" sound that gets louder as i accelerate and more pronounced (maybe just easier to hear) around a corner. I dont know what a pinhole exhaust leak sounds like though so im really not sure what it is at all. Ive opened the hood and accelerated but the engine noise wont let me hear it.. Is this the same thing?