Explain This Clutch/Transaxle Behavior

I have an SPF40 Mark II, with Roush 427SR, Quaife transaxle. I'm using the Quartermaster release bearing (721100 model), from Olthoff.

When I really get on the accelerator and while the rpms are relatively high, I have trouble getting the car out of gear with the clutch pedal all the way to the stop.

Is this a case where I don't have quite enough travel on the release bearing? The car shifts very smoothly at lower rpms.

Thanks for any insight.


Ian Anderson

Lifetime Premier Supporter
Input shaft binding in end of crankshaft.
Either not drilled deep enough or bearing not correct oillite bush not being Oillite or bell housing not being correctly aligned so shaft slightly off centre


Jac Mac

Active Member
Don't think its the shaft contacting crank issue in this case- high RPM, is the clutch cover diaphragm the type with fingers that form a 'cone' toward release bearing, @ high RPM the centrifugal force can make the 'cone' move toward the throw out bearing effectively increasing the distance & force required to release.
You had throw out bearing issues before when it over extended due to lack of clutch stop, you may need to re-visit that, maybe change type/brand.

Another possible but unlikely problem is the centrifugal forces acting on the synchro hub slider dogs of the gear in use at the time.

Rod Brace

Silver Supporter
Also have you checked to make sure that your input shaft is infact centered in the crank the make offset dowels than can correct this but it needs to be checked with a dial indicator so trans are more fussy than others I'm guessing a transaxel would be one of those. Drag racing I have had diaphragm style pressure plates when speed shifting has the clutch stick to the floor till I let off and rpm's came down then clutch pops up. Rod