only things i can think of are problems with the hydrolic system or maybe your flywheels got a few hotspots or is a bit cracked?
and my clutch had a bloody slip yesterday
was dfiting right at the top end of 3rd tho, up a a indicated 100mph
i think it was only due to one of the rear brakes binding for a bit due to some bits of tyre getting wrapped around the caliper/handbrake bit.....