PDA

View Full Version : TR6 TR-6 Clutch disengagement issues, recurring or solved ?



Tirebiter
04-04-2013, 11:23 PM
I'm trying to find some information which might be useful for me to know. I have read many, many reports about the clutch components used in the TR-6. I have also read many, many articles and reports of poorly designed parts and just as many remedies and suggested replacement parts. I find that everything from the pressure plate to the thowout bearing to the hydraulic cylinders has been suspect and categorically blamed and hearalded, depending on who's words I am reading. It seems odd, there is still no overwhelmingly obvious fix that everyone agrees on and addresses the problem once and for all. If there is, I have not read it yet. While I'm at it, does anyone have information concerning the clamping pressure of the various pressure plates that are available. I don't mean release pressure-when the clutch disengages. I mean how tightly do the various pressure plates compress the driven clutch disc when your foot is off the pedal. I know if you have a zillion horsepower, you need a heavier pressure plate. If you have very little horsepower a lighter pressure plate will be sufficient to prevent premature wear of the friction material on the clutch driven disc. I cannot find much info except that BPNW lists two different Borg & Beck clutch kits that show a clamping pressure of xxx and xxx "dn"s. Can anyone tell me what a "dn" is ? Another bit of information I would like to find if anyone has it, is how far does the friction surface of the pressure plate move when the fingers are pushed. Do the fingers bend appreciably ? I know there are some people who have made tests and calculations on hydraulic pressure and lever-arm ratios and such. I cannot find anyone who has looked at and reported the lever-arm ratios in the various clutch pressure plates. The (long lever-arm) ratio between the diameter of the throwout bearing contact surface where it pushes on the fingers on the pressure plate diaphragm and the diameter of the pivot ring or circle of the diaphragm (fulcrum) and the diameter of the outermost edge of the diaphragm (short lever-arm)where it pushes on the back of the friction surface of the pressure plate. Any help would be appreciated.

John_Mc
04-05-2013, 01:10 AM
I'm no expert on clutch issues, as I still seem to be dealing with some of my own, but the most information I've seen posted was on the Buckeye Triumphs webpage.

Here it is if you haven't already seen it:
https://www.buckeyetriumphs.org/technical/technical.htm

TR3driver
04-05-2013, 06:38 AM
It seems odd, there is still no overwhelmingly obvious fix that everyone agrees on and addresses the problem once and for all.
IMO, that's because there is no single problem. Instead there are many different problems, some of which have multiple solutions. A prime example is the problem with defective replacement throw-out bearings, which has prompted quite a few different "solutions".

Here's some good advice from Borg & Beck
https://docs.google.com/file/d/0B2H2NJt34OffZWozbjFTak1EelE/edit?usp=sharing

And in case you haven't seen it, an article on what I suspect is the "heavy duty" clutch available from BPNW (and others)
https://www.vtr.org/maintain/clutch-laycock.pdf

FWIW, I have a TR6 clutch in my TR3 (along with the TR6 gearbox). Luk pressure plate with a B&B friction plate (it says somewhere never to do that but I couldn't find any reason why not) & RHP throwout bearing. With about 50,000 miles on that setup, I had a chance to inspect it (while moving from my wrecked TR3A to the current TR3) and it all looked so good that I just reinstalled it as-is. It now has another 20,000 miles and is still working fine. Only issue is that sometimes on a cold morning, it will chatter a little bit until it warms up.

The changes I made were:
1) Use "dry moly" to lubricate snout and splines. It can't pick up dirt and get sticky over time like grease can.
2) Used the TR3 style brass bushings for the clutch shaft.
3) Added grease zerks to lube the bushings on occasion.
4) Reinforced the taper pin with a 1/4" Grade 8 bolt.
5) Kept the TR3 clutch slave setup, with a return spring and adjustment.

Sorry, can't help with the measurements. But I'd stay away from anything labeled "heavy duty" unless your engine is making over 200 hp and/or you plan to do a lot of drag racing.

titanic
04-05-2013, 02:57 PM
The Buckeye clutch articles pretty much covers all of the clutch problems, especially the explanation of why the fork pin breaks (see operating shaft overhaul and improved pin). IMHO the release problem (especially the later cars with the .700" master cyl.) is caused by a hydraulic system that is marginal. If there is any air or leakage in the cyls, wear in the linkage, or fork pin, there is not enough movement of the slave cyl. rod to release the clutch. Keep on top of the maintainance in those areas, and the clutch will be as reliable as any other car. Also, a plug for Dot 5 fluid. I have just had to rebuild the master&slave cyls after 13 years. Berry

philstr6
04-05-2013, 04:07 PM
when you have your flywheel surfaced have the machine shop step the flywheel at .008 this will give you more clamping pressure without feeling it in the clutch pedal
Philstr6
Phil

smaceng
04-06-2013, 12:23 PM
Thought I would pass this recent experience along with this thread. I am raising from the dead a 1970 TR6, and getting the clutch to work. I could just barely get enough travel with the pedal on the floor and the slave rod in the top hole to get the clutch to release. I then took a look at the clutch m/c and cllutch pedal. I found very elongated holes in both. I'm sure once I fix these, the clutch hopefully will return to a more normal one!
Scott in CA

TR3driver
04-06-2013, 03:44 PM
Yup, very common issue. Seems that practically no one thinks to oil those joints from time to time.

As a temporary (yeah, right) workaround on the Stag, I was able to ream the holes oversize and somewhat round and use an oversize pin made from an 8mm bolt; without removing the pedal or MC from the car. Hokey, but I really wanted to get driving and removing the pedals looked like a major chore.