Hey guys, just trying to diagnose a slight annoyance I have with the M. As title states, I'm experiencing a mild grinding noise in 4th and 5th gear (only) at about 40 mph, ceasing when accelerating through about 55. Noise seems to be coming from somewhere in the rear of the vehicle, and the best description I can give is that it sounds like I'm rubbing tires to rear fenders (which it could be, though it seems weird that it would only do this in a particular speed range). The noise is only when I am on the throttle, so if I let off it goes away. No clunking, no noticeable vibration, no whining, and it is the same going straight as it is in a turn. What do you guys think it could be? FWIW here are the drivetrain, suspension mods to the car ("new" stuff being about 3k miles old now):
Drivetrain:
ZF e36m3 5-speed transmission with all new seals.
Lightweight flywheel.
New satch clutch / pilot bearing.
New starter.
S3.25 limited slip differential with all new seals.
UUC short shifter kit.
Suspension:
Ireland Engineering stage 3 springs.
New Bilstein sports struts and shocks.
Ireland Engineering (S.T.?) sway bar kit with front and rear reinforcing kit.
Rear subframe w/ adjustible toe/camber weld-in plates and eccentrics.
Front adjustible camber plates
Poly subframe bushings.
Poly trailing arm bushings.
New control arms.
New m3 steering rack (w/ tie rods.)
All new bushings.
Drivetrain:
ZF e36m3 5-speed transmission with all new seals.
Lightweight flywheel.
New satch clutch / pilot bearing.
New starter.
S3.25 limited slip differential with all new seals.
UUC short shifter kit.
Suspension:
Ireland Engineering stage 3 springs.
New Bilstein sports struts and shocks.
Ireland Engineering (S.T.?) sway bar kit with front and rear reinforcing kit.
Rear subframe w/ adjustible toe/camber weld-in plates and eccentrics.
Front adjustible camber plates
Poly subframe bushings.
Poly trailing arm bushings.
New control arms.
New m3 steering rack (w/ tie rods.)
All new bushings.
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