MS3 Differential (?) Noise

My MS3, like most with Redline MT-90, makes noise in low speed sharp turns. Its common knowledge this happens with the limited slip diff and this gear oil. I can live with it. However, there is a similar noise that occurs at higher speeds but is slower. Im planning on getting a video if necessary but to try and describe it: its a "wah wah wah..." that happens about twice a second. It starts at ~73mph and gets louder until about 80mph and then decreases again past that. It decreases in speed slightly in left turns and increases slightly in right turns. I can hear it faintly around 55mph too. It seems to be coming from the driver's side underneath the car and forward, right where the transmission is. I thought it was my old and badly worn tires but I just replaced all 4 and the noise remains.

I was able to find one other person on a Mazda forum who had this problem and he claims that some friction modifier took care of the issue. Im hesitant to add the modifier because these transmissions and the synchros in particular are not the strongest around. I would like to keep this car going as long as possible. is it a bad idea to add a little?

More importantly to me, I want to know why this happens. The tires are the same size and at equal pressures. It happens over a variety of surfaces and in all lanes (road crown doesnt seem to be the problem) and is pretty consistent though on a trip I took last weekend there were a few stretches I did not hear it on. It seems to me this noise indicates that the wheels are travelling at different speeds but I dont see how thats possible. This idea is reinforced by the way the noise changes in turns. Im at a loss on this one. Its very irritating and it ruins highway trips in the car. I have a lot of travelling in the next few months and would like to resolve this. Anyone know whats going on?

sure its not a wheel bearing?

Strizzo wrote: sure its not a wheel bearing?

That was my first thought, but wheel bearing noise is typically proportional to speed. It shouldn't "go away" after 80mph

calteg wrote:

Strizzo wrote: sure its not a wheel bearing?

That was my first thought, but wheel bearing noise is typically proportional to speed. It shouldn't "go away" after 80mph

but it can get drowned out by other noises

Strizzo wrote: sure its not a wheel bearing?

That's what I'd think of first too. I can only think of one instance where I've even heard of an LSD going bad on an MS3 after trolling the Mazdaspeed forums for the last 5 years and his seems to be related to a drag run.

CV joint? The axles in that car are bulletproof, but the CV joints will get loud if they are starting to wear, or if they have lost their grease (torn boots are also common). You might also check for trans fluid loss, a seal at the shift lever will allow fluid to be ejected out the top leading to increased noise. I will also say, an aftermarket rear mount will increase any and all mechanical noises, whether or not they are anything to worry about.

Also, I had good luck with the modifier. It didn't make it silent, but it did tone down the wah-wah noise and the grabby nature, especially when backing out of a parking space or turning at low speeds in 1st and 2nd.

I don't think it's wheel bearings. I've heard those before. The wheels show no sign of play either. CV boots aren't leaking and I don't see any sign of fluid leaking from the transmission.

I have an electric Focus rear motor mount which is solid rubber. I was hoping that would be a mild upgrade that wouldn't shake me to death.

CV joints don't have to leak to be bad.