Slipping clutch under load. Options?

Enbloc

Enbloc

Senior Member
I have a '36 coupe with a lightly lightened flywheel and 9" clutch set-up. If the conditions are right, in overdrive, slogging up hill, racing, the clutch will slip. Clutch disc and pressure plate are nearly new and working perfect 99% of the time.

Is it better to convert to a 10" set-up, more friction area and stonger springs or make a mongrel by using 10" springs in a 9" housing, allowing me to keep the lighter clutch but have the higher clamping force of the 10" springs as suggested by RumbleSeat?

The 9" and 11" pressure plates have different bolt patterns. Does the 10" pressure plate share the same bolt pattern as either the smaller or larger clutch or niether?
I already have 11" and 9" drillings in my flywheel, so not having to drill another bolt pattern would be an advantage!
 
I put some .100" spacers under the springs in my 9" pressure plate to solve the same problem.
Works fine.
Need to be sure the coils don't bind up if the spacers are too thick and they need to be the same weight or it'll screw up the balance.
 
do you have plenty 1" to 1 1/2" of free pedal?, if not you may not be totally releasing the clutch
 
you got good advice from rumble seat that man knows what he is talking about as far as using a 10" pressure plate if you are using the orignal 36 trans you might have to grind the housing for clerance or go to a later case again i would follow rumble seat advise.
 
Bob G/Spanaway said:
I put some .100" spacers under the springs in my 9" pressure plate to solve the same problem.
Works fine.
Need to be sure the coils don't bind up if the spacers are too thick and they need to be the same weight or it'll screw up the balance.
Click to expand...

Another way of doing it. Thanks

alan said:
do you have plenty 1" to 1 1/2" of free pedal?, if not you may not be totally releasing the clutch
Click to expand...

Plenty of free play.

richard crow said:
you got good advice from rumble seat that man knows what he is talking about as far as using a 10" pressure plate if you are using the orignal 36 trans you might have to grind the housing for clerance or go to a later case again i would follow rumble seat advise.
Click to expand...

I have a '40 trans, so no problem with clearance issues.
 
The original Ford pressure plates have fly weights that TRIPLE the amount of force exerted on the clutch plate at high RPM. If your PP does not have the weights you may want to change PP. The weights can be seen from the inspection cover, they are on the outside of the PP.
 
Bob G/Spanaway said:
9", 10", and 11" pressure plates all have different bolt patterns.
Click to expand...

Thanks.

Terry said:
The original Ford pressure plates have fly weights that TRIPLE the amount of force exerted on the clutch plate at high RPM. If your PP does not have the weights you may want to change PP. The weights can be seen from the inspection cover, they are on the outside of the PP.
Click to expand...

Its a standard PP, so it should have the weights?
 
not really just more surface area, does the pp have a kevlar clutch surface? some folks have had that as a problem, also if it has already slipped the surface has a glaze on it already and will continue to slip unless that has been removed, just some more thoughts
 
RPM is almost certainly part of the problem here...the centrifugal system isn't coping with the loss of RPM in overdrive.
Bigger clutch will do the job but will add weight and require changing flywheel. The 9" PP I think has pockets for 9 springs but is generally built up with only 6. It could get more or stiffer springs if you can get to a rebuilder with the right stuff. That would make up for the lack of centrifugal push...the poor thing assumes engine is idling when you are actually steaming up a hill!
I would stongly prefer a rebuilt assembly here, too. I think current new ones are Chinese and have heard of problems of several types with them.

http://www.flatheadv8.org/rumblest/clutch.pdf





















































































































































































































































































































































































































































































































































































































































































































































































































































































































































































Here's the excellent clutch chapter from Rumbleseat's free online book:

http://www.flatheadv8.org/rumblest/clutch.pdf
 
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I was just thinking along the same lines when the centrifugel weights were bought into the discussion.

It is most definitely a low rpm/high load problem.

Does the 10" clutch have heavier springs compared to the 9"?
 
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