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Triumph TR3 - tr3a clutch slave cylinder

i orered a clutch slave cylinder for my 1959 tr3a.
the replacement has a 7/8" piston. the one i removed
off my tr has a 1" piston.
can the new slave cylinder with the 7/8" piston
be used and work ok?

Yes, it should work fine. I've also seen 3/4" diameter slave cylinders work. For pressure transmitted by any incompressible liquid, the Law of Pascal (Grade 10 Physics) would apply. It says, "Pressure is transmitted without any loss of pressure or force when using an incompressible liquid".

With your old 1" diameter slave cylinder, you had to apply a certain force with your left leg on the clutch pedal and the volume of hydraulic fluid it sent forward to activate the old clutch slave cylinder gave a travel of say 3/4" for the output rod coming out the lower cylinder to activate (rotate) the clutch input mechanism.

The new slave clyinder will transmit the same force, but having a smaller internal diameter (hence also a smaller volume) the output rod will come out further (say about 1") for the same force applied by your left leg on the clutch pedal.

You should re-check the free play in the lower rod as per the book after putting it all together again.

If all the fluid drained out the hose when you took it off, you'll need to re-fill the clutch reservoir with the same kind of brake fluid and then bleed the clutch line. There is also at special technique called "Bench bleeding your master cylinder" to get rid of the air in the master cylinder before you bleed the slave cylinder and hose down below.

The Buckeye site has lots of info. See below about bleeding. It's for the brakes for a TR6 but the principles are the same for any car and for the clutch system too.

Don Elliott, 1958 TR3A,

Don Elliott

Here is the VTR site with details how to Bench Bleed a Master Cylinder :-

Don Elliott, 1958 TR3A
Don Elliott

This thread was discussed between 21/03/2003 and 22/03/2003

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