Excessive engine revs when winding out: could the clutch be slipping?

[roadsterdude]

Took the 280 out for a spirited drive and noticed that when passing a line of cars in 5th gear at about 5000 RPM that the engine would surge wildly, raising rpm without resulting increase in speed.  This is a 5-speed manual ZF transmission (retrofitted long before I bought the car).  Becoming concerned, I pulled off onto a long entrance ramp and ran it up to 6000 or so in 2nd, and 3rd with the same disquieting result.  My clutch operates well from takeoff and shifts smoothly through the gears, pressure point is about half-way out and plenty of travel after release, but when revving at high RPM I am not having power transfer to the wheels.  Is this a known problem with Pagodas, or with 5-speed ZF's?  Guesses??

[ctaylor738]

Not a problem you hear about much with our cars, but certainly possible.  The engine hits its peak torque and the clutch starts to slip.  Could be a tired pressure plate or worn disk.  It could also be an issue with the clutch master cylinder not allowing fluid to bleed back up into the reservoir as the fluid heats up and expands and depresses the clutch a small amount.

If this were happening to my car, I would start by replacing the master cylinder and flexible hose And bleed/flush the system.

Cheers,

CT

[Jack Jones]

Hi Mike,

Any time I have run into this issue it has been a worn clutch disc or severely glazed disc/pressure plate. The first signs are always in the higher gears and what will usually follows is the same inability for the clutch to grip in the lower gears and eventually require replacement. Hydraulic issues usually cause a failure to disengage the clutch when you depress the pedal causing grinding etc.
Jack

[wjsvb ✝︎]

Try this:  as the revs start to climb, let off the accelerator without disengaging the clutch.  If the revs drop back to where they should be (given the speed/gear) it's clutch and/or pressure plate.  Then try slowly accelerating.  If it doesn't wind back up there is some life left in it.  A friend drove his 57 Ponton like this for nearly 10 years, from house to station and back.  You probably don't want to do that.

[roadsterdude]

Thanks for the replies.  This is what I feared.  I researched the topic through past threads and hoped that I could make an adjustment at the slave cyl, as there were a couple of posts about that, but these were obviously 230/250's that had a return spring and adjusting nut on the slave pin.  Mine (and I assume all 280's) has a self adjusting slave with no return spring, and no threaded pin/nut so I am back to square one, and believe I have a worn clutch disc.  My symptoms are as stated - it slips under hard acceleration in higher gears and if I back off it returns to a normal feel.  As you say, it is drivable, but not much fun for spirited driving at speed.  I guess I will have to research clutch replacement.  Thanks again!!