My car is an 03 coupe MN6. I just had AR headers and hi/flow cats installed at Carlisle this past August. Driving the car yesterday to and from work, I noticed a noise that can only be described as feeling and sounding like a tire rubbing an inner fender well. Did not really pay that much attention to it at first with the noise of the exhaust and all. This noise only occurs when I pull the wheel to the right at higher speed. It does not take much of a pull on the wheel to get the rubbing feeling through the wheel and floorboard. When the car is straight ahead at speed, nothing. If I pull the wheel left, nothing. I feel it through the steering and in my feet more than anything. After getting home last night, I let the car cool down for 30 min and then drove it again after checking for anything obvious that might be rubbing one of the tires. I put the car in some tight circles and the noise and feeling through the wheel did not appear to be there.

The car only has 11,686 mi on it. A couple of years ago, I had the MN 6 fulid changed to Red Line D4 at the dealer. The tech accidentally drained the rear diff before he realized I reqeusted service on the tranny. He replaced the diff fluid but did not note anything on my bill. Mistake on my part as I am not sure what he put in there or if he added limited slip additive. I had planned to replace the rear diff fluid with Royal Purple 75W 90 this month with my annual oil change.

Any advise on what you guys think this noise might be is appreciated. I found some similar posts when I did a search. I suspect the rear diff fluid. Do you think a fluid change will fix the issue. With the RP, it states that the friction modifier for limited slip diffs is already added. I was not planning on adding any GM limited slip additive. Should I use the GM limited slip additive anyway. Thanks in advance for your guidance.

 

Anybody? ttt

 

First off, no limited slip additive is needed with royal purple dif fluid.

Secondly,if you are feeling this in the steering wheel and floorboard,I would suggest it is coming from the front and not the rear.

It could be a tire rub up front,but my gut tells me it may be a wheel bearing....

It is a little confusing because you think it is the rear end, but the sound/vibration is up front

You have pretty low mileage for a wheel bearing issue,unless you inadvertantly smacked a curb pretty good or something of that sort.
I would look into that first I think,unless you KNOW it is coming from the rear

 

Thanks for your post. I took the plunge today and decided to service my car myself rather than wait for the stealership. I changed the rear diff fluid and put in the Royal Purple. I also did my normal annual oil change. Took a couple of hours. You should have seen the stuff that came out of the diff. It looked as thin as water. Probably been 2.5 - 3 years since it was changed. I was figuring on miles rather than time.

I think the RP made the difference. I will not know until I can get the car our for a long drive and really heat up the diff. Inital drive went very well. I did some figure eights in a parking lot to test for noise and distribute the fluid in the clutch packs. The car felt very smooth.

Thanks again for the post.