• Hey Guest!
    British Car Forum has been supporting enthusiasts for over 25 years by providing a great place to share our love for British cars. You can support our efforts by upgrading your membership for less than the dues of most car clubs. There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Upgraded members don't see this banner, nor will you see the Google ads that appear on the site.)
Tips
Tips

Sticky Clutch

Share this page

Dugger

Dugger

Senior Member
Offline
Since I am a new member of this forum, and the first "Basil" law is not to lurk, I thought I would post a problem I am having with my 'brand new' clutch.

To make a long stroy short, I lost my transmission last year on a trip to a show in Birmingham, AL. Forunately I had a spare freshly rebuilt transmission that I could drop in. Since I was pulling the tranny anyway, I felt it would be a good idea to change out the clutch and clutch cover (also known as pressure plate in other circles) release bearing, fork pins, fork shaft bushings, etc., while it was apart.

Good news, the transmission works well, Bad news the clutch sticks when hot. I pulled the transmission again thinking that the release bearing sleeve may be sticking on the front oil seal cover, but I could not find any evidence of that. I pulled the clutch and cover off the flywheel to check for runout and if there may have been some errant grease on either, but this proved negative also. I polished the front cover and the inside of the carrier, applied a high temperature lithium grease to carrier and reassembled.

Again it worked great...until it heated up, then it starts sticking again. The clutch pedal feels like your rolling over BB's.

Where would you suspect I should look for the solution?
 
Hello Dugger,
since you have re-checked the mechanical side, I would have a good look at the hydraulics. Exactly what do you mean by sticking, does the clutch release and allow a gear selection and then not re-engage? or does it not release? You don't say what car, but some Triumphs use a plastic pipe to feed the slave and this is known to be affected by heat which in turn prevents full clutch release. I also don't know what BB's are but the clutch action in the instance I mention is usually not affected, basically the hydraulic pressure inflates the clutch pipe rather than operate the clutch.

Alec
 
Hi Dugger,

Having just done the clutch job, you might already know this...

The TR2/3/4/5/250/6 (if we're talking about one of these) all use a similar mounting bracket for the slave cylinder that mounts a little oddly. It goes on one side of bellhousing-to-engine flange. It's easy to accidentally mounted on the "wrong side" of the flange, which will make for very little if any free play in the system and might cause symptoms like you describe.

Just a thought!

Cheers!

Alan
 
Welcome to the madness, Mike! Glad you're on board. Careful - it's addictive. /ubbthreads/images/graemlins/jester.gif

Mickey
 
Thanks for the response.

I guess I forgot to mention that this is a '71 TR6.

The Hydraulic side definitely came to mind after twice pulling the transmission. I replace the master/slave and the original nylon lead with new parts.

I remember reading somewhere that the clutch fork arm should move ~.625" (16mm) when all things are working correctly. This one moves only about .5" (12mm). I have checked the pedal connection and the fork shaft connection for wear,but didn't find anything out of normal clearances.

Once the clutch heats up, I need to firewall the pedal to get the clutch to release.

Okay, I will try and explain the reaction of the pedal during operation a little better than "BB's". THe pedal feels like your running your heel over several small pipes.
The clutch operation grabs instead of smoothly engaging.

Does this sound like the clutch disk is expanding when it is heating up?

I guess I forgot to mention that this was a '71 TR6.
 
The slave cylinder mounting plate is located on the front side of the engine/transmission flange with the ears of the slave cylinder on the rear of this plate.

Is that correct?
 
Hello Dugger,
if your travel is reduced then I would suspect that nylon line.
I always replace that with a (home fabricated) metal line. Note that this is 1\4" rather than the brake 3\16".

Alec
 
I replaced the nylon line with a braided SS line from Moss.
 
Hate to mention it but since you are slowly eliminating other suspects... did you verify the condition of the clutch fork pin? (or better yet did you replace it?). A broken pin can deliver partial and inconsistent operation as the break can be a ragged shear that still catches enough for partial operation.
 
I replaced the clutch fork pin, carrier pins, shaft bushings. I suspect one or more of the 'new' parts was not up to spec.
Can anyone tell me what their travel is on the shaft arm?
 
Hi again,

Let's talk about the release bearing (or throwout bearing, in some circles).

Did you use a special tool to install it? Or, just the old "press it into place with a vise" method?

If the latter, this often damages these bearings. It's a possible cause of your problem, although usually the release bearing will work for a while, failing early after some 5000 or 10,000 or 20,000 miles.

The correct way to install is to turn the bearing while it's being pressed into place. TRF sells a simple tool to do the installation, or offers pre-installed bearings and carriers.

Just a thought.

Alan
 
Dugger,
One other thought which may be rare. On a previous clutch cover replacement I ordered a B&B rebuilt cover. It looked perfect & is certainly a rebuildable part. When I reinstalled the trany I had to use the bottom hole on the shaft arm or the shifting would be difficult when warm. The other operation of the clutch was normal & silent with no "marble " effect that you describe. I would try the bottom hole on the arm before anything else but it doesn't explain the other symtoms you have.

Lose of slave clyinder travel can also be caused by worn pedel pivots in the pedel box. These pivot points commonly ware from use over the years & the leverage used to apply the force to release the clutch. I have seen many of theses completly egged out. This can be fixed by opening the hole slightly & pressing in a bronze bushing. I'd be willing to bet if every one checked, they would see excess ware at this spot in there own car. Not as complicated a repair as it sounds.
 
I used a home made press-turn tool to install the release bearing. Pretty simple device really. Although I am not happy with the squeeling noise the bearing makes during operation. Not to mention this is the second bearing I have gotten; the first being bad out of the box. I was told that these bearings were self-lubricated and don't need any prep before installing - considering the noise this bearing makes, I am not sure that is correct. I am almost sure I will have to drop the transmission again in the future and at that time I think I am going to replace the bearing and carrier with a Gurnst unit. I will also take the clutch and cover to a machine shop and have them checked. Both units were new when installed, but this wouldn't be the first time a clutch cover had a bad spring, or the clutch separated when hot.
 
You said you transferred the connecting pin from the slave cylinder to the bottom hole of the cross shaft arm?
That would lessen the travel of the release bearing and in my case, I wouldn't be able to disengage the tranny at all. I have considered transferring the pin to the top hole which should eliminate the firewalling of the pedal to disengage the clutch, but it would increase the pressure the release bearing maintains on the clutch cover causing earlier failure of both.

It is my impression that when BL reduced the master cylinder size from .75 to .70 inches (for a softer clutch that the ladies would like) they eliminated almost all of their operational margin. Just another typical situation where marketing/accounting people controlling engineering.

btw: I did check the pedal box and it seems to be in good condition. No egging of the pin hole.
 
My mistake on the pin placement. The top pin is correct, I keep think'n I'm under the car looking up /ubbthreads/images/graemlins/wink.gif

I think the Gunst will solve the "marble" feeling of the problem as well as easing up on clutch pedel pressure a little. There was a bad batch of original style TO bearings around, don't know how many are left, but in either case the Gunst is superior in every way. The squeeling noise is usually generated by the bearing rubbing on the spring fingers while spinning up to speed which could mean an uneven finger pressure. It could also be caused by the bearing carrier "tilting" at the extreme end of the nose cover. The Gunst assembly recomends a preload which I have chosen not to use & it works fine, some have also had some squeeling & the preload resolved that. What ever works. I just was not comfortable with the constant load on the thrust washer.

P.S. I have installed all of my previous TO bearings by freezing the bearing carrier & slightly warming the bearing in the oven (not enough to melt the grease), then just assembling them . This a low interferance fit.

P.S.S. If you are pulling the trany again I would highly recomend drilling a secondary hole through the fork & install a hardened auxiliary bolt. If you need pics of one let me know. There's really only one spot to drill.
 
I also froze the carrier prior to assembly, but didn't heat the bearing.
I gather that there has been a rash of bad TO bearings.

Sounds like I may have the solution to the problem.

If the bearing is bad, then the pedal would feel rough, because the TO bearing is not rolling smoothly with the clutch cover, thereby setting up a vibration in the system causing the clutch plate to grab - okay I am wandering around after every straw. This wouldn't explain the pedal travel needed to disengage the clutch.

On the second tranny removal (I am getting pretty quick at this now - under 3 hours including the interior) I checked the carrier on the rebuilt transmission thinking that it could be the shorter version from a TR4, but it was the correct length. This was when I replaced the original defective TO bearing.

I would love to try an original bronze carrier, if I could find a decent one. I guess I could have a machine shop fabricate one.
 
My TR4 has an occasional squealing noise from the clutch. Sort of high pitched when the petal is released. Then it goes away with the next stroke of the pedal. Could this be what you are describing?
 
Back
Top