My 67 Austin Ute is starting to get clutch shudder when taking off in 1st gear. Only happens when it gets good and warmed up. Doesn't exist at all when cold. It usually takes a good highway run to get it to act up. It has a detuned version of the 1622 as used in the MGA Mark II with the 3-synchro trans. Any ideas what's up? TIA, Larry Daniels