TR2/3/3A tr3 -- 7/8 or 1 inch slave cylinders

[sp53]

Hello tr3 people. Does the difference between a 7/8 slave cylinder and a 1 inch slave cylinder effect the life of clutch. I am curious about this possibility because the 7/8 slave just engages harder and more direct. It would seem to me that this would put more strain on the u joints and pressure plate. Either I am dreaming or the 1 inch slave cylinder operates smoother and less direct. Possibly causing less wear?

George

 

[martx-5]

The amount of force neccessary to dis-engage the clutch is the same no matter what size cylinder you use. The difference in the cylinder sizes affects how much force you have to push with your foot. The larger cylinder requires less force from you, but because there is more fluid to displace, you have to move further through the stroke to get the same movement on the throw-out bearing. I would say that translates to smoother, but less direct.

 

[Alan_Myers]

Hi George,

The previous answer is correct.

A problem that could occur with too large a slave cylinder is insufficient range of movement for accurate adjustment. This could lead to a more quickly worn out throwout bearing, if adjustment is such that the T.O. bearing drags. At the other end of the adjustment range, the clutch might not disengage all the way and shifting would be more difficult, could lead to gearbox problems eventually.

I may be wrong, but I thought .70" and 3/4" were the two sizes of clutch slave cylinders used on all the TRs, with the switch to 3/4" coming in the middle of TR6 production. I seem to recall TR2 and early TR3 used a .70" with a differently threaded hose fitting, but otherwise the same as used on later TR3/3A, TR4/4A, 250/5 and early TR6.

TR6 was switched to using a non-adjustable slave cylinder pushrod. That and a heavier-operating diaphragm type clutch (in use since TR4A) lead to some problems with short clutch/T.O. bearing life, probably are the reasons the switch was made to a slightly larger .75" slave cylinder.

Also effecting the geometry of the clutch release mechanism is which of the three holes in the release shaft lever is used to connect the clutch cylinder push rod. All TRs use the middle hole. Top or bottom will give incorrect range of motion and either make the clutch too heavy or give too little release motion.

I don't think there is much if any effect on the U-joints, no matter which clutch slave cylinder is used. Smooth shifts are the best way to help U-joints stay healthy.

I had a non-greasable set of U-joints in my TR4 for 25 years - just recently replaced with greasable type - but not really showing any wear I could detect, despite some pretty hard driving and a modest racing career. The only problem was re-occuring loosening of the 8 fasteners, which I hope is solved now with the upgraded bolt and all-metal-locking nut set I got from The Roadster Factory and installed with Locktite for added security.

Hope this helps.

Alan

 

[sp53]

Thanks Martx-5 your explanation cleared up most of what I could not wrap my mind around. (The larger cylinder requires less force from you, but because there is more fluid to displace, you have to move further through the stroke to get the same movement on the throw-out bearing) I guess what comes to mind now is the directness and the shorter time it takes for the system to work. In the past, I just accepted the slower movement of the 1 inch slave cylinder on the clutch because that is all I knew. Now it is quicker. Perhaps that is what I am experiencing? The quickness that feels like it is placing more force on the drive train. I guess the force would be the same, but the car is so different. And yes, I do not have push the clutch in as far.

George