'04 WRX with about 3800mi... Mobil 1 10W-30 in the engine, and factory fill in the tranny/rear diff.

I really don't like the feel, sound, or rattle of my tranny. It's not outrageous, but I want to smooth it out, especially in 3rd gear which rattle badly.

Someone suggested M1. Someone else suggested that M1 would be bad news for the tranny.

I also might be able a hold of some RP product around here (N. VA).

Am I overly optimistic to think that synth in the box will help? Suggestions? Thanks!

(p.s. yes, I did a search, but yielded little/nothing from last 3 mo)

Try putting 2-4 pounds more pressure in the front tires relative to the rears. This made my "deceleration" noise all but disappear.

The jury is out on synthetic transmission fluid. Many have experienced grinding gears. I have redline 75-90NS in my box and I'm going back to GL-5 dino soon.