Rear End Howl

[BigNic]

I have developed a noise above 45 MPH coming from the rear of my 98 convertible. Have it in to my local dealer and they think it is coming from the differential. It howls. Of course they have to tear into it to determine what the problem is. Has anyone else experienced this? Noticed it a couple of weeks ago and I think it has gotten worse. Has anyone else experienced this? My car only has 17000 miles on it. Any help out there.

 

[Ken]

Check your fluid level and add some of the required additive to see if maybe that's the problem. Normally if the clutches are slipping, it would make a chattering sound, not a howl, but ya never know. :eyerole It might save you a few bucks on labor costs.

 

[JT ZR-Won]

Are you running stock gears? I know the howling sound is quite common with aftermarket larger gears. If they're stock........that's a good question. I wonder if low fluid would cause that?

Jay

 

[c4c5specialist]

Hi there,
If the noise is coming from the back, only on straight line driving, it is possible that it is the gears. HOwever, if it is only in turns, there is a different fluid and friction modifier that could be used here.
Also, check the tires for any scalloping, as if the alignment is not good, it will chop the tires, also creating this type of noise.
Does the noise get louder or softer when you attempt to take a turn???
Please answer these questions, and we can proceed, c4c5

 

[BigNic]

Thanks for you reply. The noise is going straight line. Starts about 45 MPH. I haven't noticed it on cornering. Looked at the tires and couldn't see any obvious scalloping. A point of information, the car had been lowered, I raised it up back to stock and had a complete alignment done. I don't have the final specs in front of me but both rear and front toe-in was out significantly after raising it and they were brought back in spec. Minor tweaking of caster/camber on front and rear. I have the car in to my local Chevrolet dealership. Their diagnosis is differential problems and want to tear in to it. Big bucks. Estimate is $2500. There is a debate about rebuilding vs new drop in. Supposedly they are rebuildable but the factory doesn't recommend it. (According to my local dealership). Considered adding more friction modifier but haven't noticed any noise on cornering. The tire scenerio feels like a more likely problem but short of replacment I don't know what to do. Another point of info, I didn't notice the howl immediately following the alignment. It took a couple of weeks before it was obvious.

 

[JT ZR-Won]

Is the car your daily driver? If you've got something else to drive that will give you a little time to figure something out. Personally, I wouldn't pay $2500 to have the exact same differential put in the car. For $1,300 you could go with a set of 3.73's by Mallett.
If the car's on a lift, I wonder why they can't pin-point where the noise is coming from? That's the dealer for ya:eyerole I can't see lowering the car having anything to do with the howling.....

What about another opinion.........maybe from a couple of local speedshops?

Jay

 

[GreyGhost]

Simple Check

BigNic:

Before you do anything major simply try rotating your tires front to back and see if that makes a difference. If not, put it on a transmission type lift and run the car at various speeds until you determine where the noise is coming from.

Just a couple of simple suggestions,
__________
:cool
Al

 

[c4c5specialist]

Rear end

Hi there,
Per GM VME, we are under strict orders, unless you are doing an end cover seal, we CANNOT overhaul the rear differential on the c5.
The reason is that we cannot set the correct side carrier preload, because the jig is like 1500 dollars, and has NOT been sent to any dealers as of yet.
Personally, by an entire unit, and then proceed with the install.
I caution that after you had the alignment done, this noise started, I feel that maybe you should get a seconde opinion here.
Another thing, does the noise change pitch when you accel or decelerate the car?? Is it sensitive to engine speed, NOT vehicle speed?? Does it sound louder when you are just cruising, or when you are really on it??
Let us know, c4c5