Rear End Whining

[RP96]

I posted a thread several weeks ago about a whining heard in my 1996 LT4. I thought it was in the 6 speed tranny. After closer inspection and testing, it appears to actually be coming from the rear end. There is less than 11,000 miles on the car. The whine is most noticeable at 65 to 70mph, although you can faintly hear it at lower speeds. The volume seems to vary with the temperature of the air outside. The hotter it is, the louder it whines. Any thoughts? Thanks.

 

[Vettelt193]

try changing the rear end fluid... use a good quality synthetic like red line. this may be a quick fix for the whine

 

[Shriker]

Definitely start with the easy , changing the fluid. It is most likely just old and the friction modifier does eventually break down. My LT-4 has 60K on it and I changed mine after hearing some rear end noises going around slow corners.

Good Luck......

 

[cntrhub]

Take that puppy for a nice ride. Get the rear end hot and then dump the oil. You want as much suspended contaminants out of the rear end as possible. It might be too late. The damage may have been done already.
Drive Noise is most evident during constant acceleration throughout the speed range. Coast Noise is when the car is allowed to coast through the speed range with the throttle closed but with the car in gear. Float Noise is evident while just bearely holding the car speed constant on a level road at any given speed.
Differential Side and Pinion Gear Noise cause noise during straight ahead driving and will be most pronounced on turns. Pinion Bearing Noise is a continuous low pitched whirring noise starting at a relatively low speed.
It will be hard to clean the rear end, short of (ideally) pouring in half kerosine/half oil, warm up the rear end again, and then dump it all out.
It would be wise to fill the oil back up, (without the additive) drive another heat cycle, and drain that oil again to check for more partical debris. Then fill the proper amount of oil with the additive, and test ride again. If the noise is still there, you can either turn up the radio loud enough to override the noise, or monitor it until it's so loud, you have to go for a rebuild.
And yes, if you read a factory manual, they do have an audio value that if you CANNOT hear the rear end noise using the radio at a reasonable volume, it is normal noise.

 

[RP96]

Thanks folks. One additional question: As I said, at first I thought it was the transmission. At that time I talked to a service manager at a local Chevy dealership about changing the oil in the tranny to synthetic oil. He strongly advised against it because some trannys are put together with what I think he called RTV(room temperature) sealant. Using synthetic oil with that type of sealant causes major leaks. Does the same hold true for the rear end? Thanks again.

 

[cntrhub]

There is Synthetic 75-90 gear lube (GM Part No. 12345836) used in front drive assemblies on the K-Truck Models. I'd stick with the recommended oil the Vette rear end calls for. You call the ball.

 

[Vettelt193]

I use synthetic all around, no leaks (at least no leaks on my '93... I haven't switched my '96 over yet)

 

[RP96]

Thanks to all who suggested changing the rear end fluid. However, everyone seemed to imply that it is an easy job. I got under the car last night; and checked a service manual today and it appears that I need to tear the whole rear suspension apart just to change the fluid. Am I missing something? Is there an easier way? Thanks.

 

[CYA]

RP96,

I believe that you are going to remove the fluid from the check level/fill hole by drawing the fluid out (siphoning).

I'm sure that other members can describe it better.

By the way, my GS started whining with 600 miles, giving me the exact symptoms you are describing. I'm picking up the lube and additive tomorrow and hope the condition clears up.

Curious if anyone else has dealt with this WHINING and had luck with a lube change?

 

[Hib Halverson]

If this faint axle noise at highway speeds has always been there or you've just noticed it but it's not gotten worse, you can try changing the axle lube. That may or may not make a difference. Since there's only 11,000 miles on the axle, I'd think the noise will not be changed---but I'm just guessing.

If this is a case where, in a short period of time, you noticed the noise and then noticed it's getting louder, also, change the lube, but be prepared, the problem might not be repairable with a lubricant change.

The factory-fill lube in a 96, was not synthetic though the D44 works well with synthetic lubricants. I've used them with good results in my 95 since I bought it in 95.

If you switch to synthetic, follow the synthetic manufacturer's recommendation for any limited slip additive. Some synthetics are not compaitible with GM's additive. Some synthetic makers may want you to use their own additive.

The suggestion of driving the car until the axle is at operating temperature before siphoning out the old lube is a good one. I'd let the car cool for 20-30 min after the drive. It will be less painful to change the oil and in that short time, you're not going to have a problems with contaminants settling out .

 

[sothpaw]

rear end

I have a loud brrrr sound which the mechanic says is the rear
end. It has been that way since I can remember--maybe 25000
mi.

I've changed the diff twice in that time, to no avail.

Mechanic says that the diff fluid should have been changed in
the first 15 k mi and since it was not, I will be buying a diff
sometime soon (another 10-15K mi?). It this happens, I will
retailate with a 3.73 gear box!

The noise occurs in 5th and 6th at 50 and up (or at least that's when I notice it). It is especially prominant if you try to maintain
your speed in 6th at cruising speed.

I never hear the noise in 1-4 as these are lower speed and even
if I was in 4th at 110 mph, the engine would be too loud and
my attention else where!