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TR2/3/3A Position/Adjustment of TR3A Clutch Slave Cylinder

Motopsyche

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It's clear I'm losing my mind, but that doesn't stop me from doing things under a car. However, a little help is in order tonight...

I'm repositioning the clutch slave cylinder on my '60 TR3A, and I'm unsure about the "correct" order of things; specifically, the sequence of the cylinder mounting bracket and whether the cylinder goes on the bracket from the front of the car or the rear. The bracket on my car was originally mounted on the rear side of the transmission flange, and something tells me that's not right, so it's been moved to the front side of the bellhousing flange.

Now for the mind-losing part. When setting the .01" play in the rod (page 116 in Haynes), should the return spring be mounted to draw the rod fully into the cylinder? Or should the adjustment be made without the spring mounted so that the piston in the slave cylinder is pushed outward by the internal spring toward the clutch?

For the record, I have the model of clutch slave cylinder that Haynes identifies as being for the TR4, 4A.

Guidance on these points would be greatly appreciated.
 

TR3driver

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Here's the correct assembly:

Fig32Clutchslavecylindersmall.jpg


There should not be an internal spring in the slave cylinder. Although some replacements come with a spring, it is not used in the TR3A application. Just take it out.

The adjustment procedure is intended to work with the return spring installed. Step 1 (screw the rod out until all clearance has been removed) is supposed to expand the pushrod against the return spring, until the piston is bottomed in the slave and the throwout bearing is starting to depress the clutch fingers. Then steps 2 & 3 basically turn the rod back into the clevis enough to set the clearance.

In practice, the clearance is not nearly as critical as the book makes it sound. As long as there is _some_ clearance, the clutch will work fine. I generally check mine by just pulling the lever away from the slave (against the return spring) and wiggling the lever. If I can feel it rattle against the piston, there is enough clearance.

PS, I believe the value given in the Haynes is incorrect. The correct number (for later cars with Girling brakes) is 0.100", not 0.010". See below for a clip from the factory manual.
 
M

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Randall,

This sounds very useful, but for us complete novices (willing and anxious to learn), could you be a bit more detailed on Step 1 (i.e., could you perhaps label the parts to coincide with your instructions, or perhaps a labeled illustration like the ones you have provided for other procedures).

BTW. In your picture above, I don't see the return spring.

Thanking you in advance for "Clutch adjustment 101.
 

TR3driver

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The return spring is there, it's just kind of hidden behind the cylinder & pushrod. If you look just below the nut (item 2), you can see part of the spring end.

I don't have time at the moment to do a write-up; but maybe this will help:

First a clearer photo (from the TR4 workshop manual)
Fig6Clutchslavecylinderlinkage.jpg


And the procedure
Fig6procedure.jpg


PS, the 'correct' adjustment is 1/10" (0.100"), not .010" as above and in some manuals. But the clutch will work fine with only .010"; the larger number just gives more margin for wear before it has to be adjusted again. The clearance closes up as the friction plate wears, and it's quite important that it not go all the way to zero (which could cause a slipping clutch and rapid wear).
 
OP
M

Motopsyche

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Randall,

As always, your guidance is very helpful. The internal spring was an interesting feature in that it is shown in several parts listings, but its function would seems dubious. Could it have been meant to prevent the piston from "bottoming out" when the larger external spring returns the piston to rest at the back of the cylinder?

All the best!

Bill
 

TR3driver

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Motopsyche said:
Could it have been meant to prevent the piston from "bottoming out" when the larger external spring returns the piston to rest at the back of the cylinder?
I don't believe so. Both the piston and the cylinder have mating 'stops' built into them, so I believe they are designed to meet there. The stops hold the seal well away from the unbored section at the back of the slave cylinder. I have also taken apart a lot of original TR3 clutch slaves over the years, and none of them had the spring inside. Plus I've covered perhaps 300,000 miles in a variety of TR3s and never had a problem from the piston "bottoming out". (Actually, having it not bottom is a potential problem source, as it leads to erratic pedal freeplay which I find irritating.)

I believe the internal spring was supplied by Girling (hence the drawings and parts catalogue entries), but was intended for use on applications like the TR4A that have no external spring.

In that case (TR4A-TR6), the internal spring holds the piston out and takes up the slack in all of the linkage, holding the TOB lightly against the pressure plate at all times and providing a "self-adjusting" feature. The TOB is a special free-turning design, so it will spin with just the light pressure from the slave spring on it.

As a side note, there are several little mistakes like that in the manuals. Seems the manual writers weren't always careful to get the right illustrations. The Stag manuals even show the clutch operating shaft installed wrong (the Stag has the clutch slave on the other side so the shaft goes in the other way around).
 

HerronScott

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TR3driver said:
And the procedure
Fig6procedure.jpg


PS, the 'correct' adjustment is 1/10" (0.100"), not .010" as above and in some manuals. But the clutch will work fine with only .010"; the larger number just gives more margin for wear before it has to be adjusted again. The clearance closes up as the friction plate wears, and it's quite important that it not go all the way to zero (which could cause a slipping clutch and rapid wear).

Randall,

Don't both of the references in the procedure you posted show 0.1"?

Scott
 

TR3driver

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HerronScott said:
Don't both of the references in the procedure you posted show 0.1"?
Yes, they do. But some other manuals have different numbers in them; for example the Haynes manual that the OP referenced says 0.01
 

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HerronScott

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Randall,

Ah, I get it. You were referring to the other information in the thread when you said above and not the procedure you posted. Sorry! :smile:

Scott
 
M

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Randall,

As always, many warm thanks for sharing your knowledge and expertise with us.
 

luke44

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I wish I could take credit but these were the pix posted by Barry Shefner. My frame is boring black.
 

luke44

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Well back to the drawing board. Moving the slave to the trans side of the mount plate definitely gets the gears to disengage and shift easily (engine running but no road test - just up on jack stands) but it’s clear there is zero clearance - ie - the tob is resting on the clutch fingers. And the piston is bottomed out. In fact it’s all under tension to get the clevis pin in.

So the slave is going back onto the engine side. Maybe I need to lengthen the clutch master rod a few turns?
 

CJD

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On my TR3A I had to modify the rod shorter to make it work properly. I think the fork pin had broken, so the PO swapped in a longer rod. Once I fixed the pin the rod was too long. Grinding shorter was easy and I saw no ill-effects for 5 years of driving.
 

luke44

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On my TR3A I had to modify the rod shorter to make it work properly. I think the fork pin had broken, so the PO swapped in a longer rod. Once I fixed the pin the rod was too long. Grinding shorter was easy and I saw no ill-effects for 5 years of driving.

That sounds like such a simple and obvious fix. I was going to get into the weeds on rod lengths etc. I can’t believe I never thought of just cutting it down. Right now the threaded rod end binds in the bottom of the fork and a shortened rod can easily give me the clearance I need. I’ll try it and report back. Thanks!
 

Graham H

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Looking at your first photo above because of the wear mark on the pushrod it would appear you have not pushed the slave piston all the way into the cylinder which is where it must be to get any adjustment right. The fluid in the line from the master cylinder pushes the piston out and there is quite a reasonable amount of effort needed to push it back in by hand and you will find the need to keep pushing it back in during your final setting.
if you have a standard TR3A clutch set up the slave is mounted in front of the bracket and if you can't get the clutch to release then the fork pin must be broken or there is some other problem with the setup. With everything adjusted correctly and the outer return spring fitted which is what holds the piston at the end of the cylinder, you can pull the operating lever forward and feel the free play which according to the manual is 1/10"I wouldn't shorten the pushrod.

Graham
 
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