slipping clutch but only under boost...?

[Livolsi, Stephane]

Hello all. I have never experienced an impending clutch failure before and
from what I know about clutches my symptoms don't make sense.
Car is a 1986 5KTQ, clutch was relatively new 3 years ago and have put on
about 50,000kms since then. I occasionally drive in a manner that may be
considered hard on the clutch but for the most part it's pretty tame.  New
clutch cylinder last year.

Sometimes, especially going uphill under high boost in 3rd or 4th gear,
accelerating hard, the revs will suddenly climb quickly with no
corresponding increase in vehicle speed.  I am sure the clutch is slipping
(what else could it be?) I back off the gas and accelerate a bit less
aggressively and no problem.

OK, I can accept that my clutch might be going but what doesn't make sense
is that it is not consistent.

Starting out from a standstill I can spin tires where there is sand/gravel
on the pavement.  To me this indicates good solid clutch hook up.  Sometimes
it pulls like a train at 1.3 BAR on the boost gauge with no sign of
slippage.  When the car is stopped, there is no indication of slippage if I
hold the brake, let out the clutch and give it gas (with my 3rd foot...:)).


Is this consistent with a failing clutch?  Or is there a seal somewhere that
might be getting engine oil, or tranny fluid on the clutch plate?

Thanks for any and all advice.

Stephane