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TR6 TR6 slave cylinder

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JoeC

JoeC

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I recently replaced the slave cylinder on my 76 TR6. It worked fine for a few days, but now when I depress the clutch pedal, the piston actually pushes all the way out of the cylinder. Then, of course, I have to refill & bleed the entire thing! Any suggestions on the cause?
 
JoeC, you have a clutch master problem or a hose that is crimped and not allowing the presure to be releived off the slave. Most likely the spring in the master has either broken or someone rebuilt it and didn't get it clamped down enough and the little rubber in the end of the cylinder keeps things blocked up. Wayne
 
Thanks Wayne. Your suggestion sounds logical. I purchased this TR last week. It has been sitting idle /ubbthreads/images/graemlins/cheers.giffor over a year, and the previous owner "said" he put a new master on it. It was dry due to a bad slave, so I guess it could even be clogged. I'll check all hoses and the master itself. Thanks again,
Joe
 
Hello Joe,
it sounds as though there is a problem at the clutch end. This system is designed to be self adjusting as the cylinder is quite a bit longer than the piston stroke which is determined by the volume of fluid the master cylinder delivers.
One common failure is that of the tapered bolt that secures the clutch release fork (inside the bell housing) to the actuating rod that is connected to the slave piston. If that has sheared the fork and rod will tend to rotate so that the slave piston will be further out of the bore of the cylinder. If you look at the angle between the slave cylinder push rod and the arm on the release arm, it should be greater than 90 degrees.
Also look at the way the cylinder and the mounting plate is assembled on the engine, could it have been miss assembled such that the cylinder is too far forward relative to the gearbox. Normally the piston should be far down in the cylinder at rest, (but not bottoming or the self adjust won't work) and as I said earlier the stroke is much less than the cylinder depth.

good luck,

Alec
 
Hi Joe.....
I just did a clutch master & slave cylinder rebuild a couple weekends ago.
Upon disassembly I found the spring in my MC was broken and the 2 halves had meshed themselves together making one spring that was half the proper length. The clutch was working fine like this though (only reason for rebuild was leaks) so I don't think the MC spring is the problem here.
A kink in the hose could cause the slave to not to fully retract properly then each time it's cycled it will move further out of the cylinder bore but intuitively I doubt that's the problem here./ubbthreads/images/graemlins/nonono.gif
I would get underneath and look at the actuating lever as someone else pumps the clutch to see what's happening.
I agree with Piman that it's likely a bunch of slop in the actuating lever caused by clutch shaft bushings, the dreaded taper pin on the clutch release fork or a combo of these allowing a lot of lost motion on the actuating arm thereby allowing the slave piston to move too far before releasing the clutch.
If it's any of these things then the gearbox has to come out to fix it, sorry! /ubbthreads/images/graemlins/cryin.gif
 
Well it looks as though you guys (Graham and Alec) are on to something. I removed the hose and pipe. No crimps, all clear. I also removed the master. Except for a bit of dirt, all appears to be in good shape. What I don't understand though is that after the slave replacement last week, the car drove and shifted great /ubbthreads/images/graemlins/confused.gif. Then all of a sudden, this slave piston issue arose. Well, I guess I dig deeper (into the gearbox and the wallet!)
 
Hello Joe,
that it ran fine for a while then you have this problem points to a failure of the tapered bolt. This allows the forked arm to rotate relative to the cross rod. This puts the arm on the cross rod some degrees anti clockwise looking at it and the piston is then further out than it should be. As I said look at the angle, if it is acute then the fault is inside the bellhousing. The adjustable push rod Graham suggests will not help you. (And is not necessary on a stock car, as I explained before the system is self adjusting due to the extra depth in the slave cylinder)

Alec
 
Thanks Alec,

The angle is less than 90° between the pushrod and lever, so I believe that the tapered pin (or something else) is the problem. I'll delve into it this weekend. I did snatch up the adjustable pushrod on eBay...thanks Graham...I still may be able to use it to help isolate the problem. ($35 bucks is pretty expensive for "buy it now" however) /ubbthreads/images/graemlins/pukeface.gif
 
Hello Joe,
yes, I'm afraid that the gearbox needs to come out. The taper pin is a rather poor arrangement, so take care that the new one fits snugly into both components. It's a little difficult to explain, if you are not familiar with this set up, but both the fork and the cross rod have a tapered hole and the pin\bolt needs to mate with both. It will break again if it just tightens in the cross rod so take care and if either components show damage or wear it would be prudent to replace them (Unless you enjoy taking out gearboxes that is?)

Alec
 
I saw this part on eBay; it may be something that would help you with the slave. Have you pulled the tranny yet?
AMAZING PART-TR6!!!-AS SEEN IN KAS KASTNER'S 2nd BOOK Item number: 4538614299
 
One other thing, and I'm working from memory. If you do have to replace the tappered pin then drill out the hole for the pin in the fork just big enough so you can run a punch in it to knock out the pin. The pin comes out in the direction of the transmission so you can't get to it. I had to cut a cross shaft to remove the fork one time.
 
That's a good thought Skikir. I wasn't able to remove the gearbox last weekend...hopefully I'll have time for a look this weekend. I plan to replace the tapered pin, clutch fork, pin, release bearing & holder while its all apart. /ubbthreads/images/graemlins/yesnod.gif
Thanks, Joe
 
Well...I got the gearbox out. I wish I had 3 hands and were a bit smaller! Anyway, I found a broken tapered pin and a cracked fork (where the pin enters). I've got the parts ordered, and I hope I can put everything back where it belongs. I've seen a picture of a guy who drilled through the fork and shaft (perpendicular to the tapered pin)and used a 1/4" bolt as a "back-up" in case the tapered pin failed again. Anyone seen this before?
Thanks,
Joe
 
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