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MG MGB Technical - Clutch problem

Just turned the key on the TR6 (70) after a 2 and half year refurbish job.
(I know, I know..this is the MG BBS. hey, I own a couple of MG's and always get good help over here.)
Good news...it started right up
Bad news...can't shift into any gear with the engine running.
Won't even go into 1-4, will grind when attempting reverse.
With engine off, shifts fine.
Bled the slave cylinder several times...no help

What am I missing?
(besides more hair on my head)

DS
Dennis Silance

Dennis. What you are missing is a large body of experienced people who have had many of the more common problems over the years, a few of the very uncommon problems over the years, and all with some experience on the vehicle under discussion. Thus, we cannot give you the indepth help that we can provide with an MGB.

Your basic problem is that the clutch is not releasing sufficiently from the engagement with the flywheel that the transmission can be shifted without the gears grinding. I would assume that there are two possible causes for this:

First, the clutch release mechanism is not moving the release bearing (throw out bearing) sufficiently that it adequately depresses the release mechanism on the pressure plate and the pressure plate is still being held to the flywheel with sufficient pressure that the input shaft is not being disconnected from the engine drive.

Second, the clutch release mechanism is working correctly but the clutch plate (driven plate) is not releasing its grip on the flywheel. This could be caused by the clutch plate being stuck onto the flywheel (as we see with cars which have been sitting for a while), or that the clutch plate is not capable of disengaging for assembly reasons (does the Triumph clutch plate have a "this side towards flywheel marking?).

That is all that can cause the problem you describe if it is related to the clutch. With an MGB, we could be confident to narrow the problem in this manner. With a Triumph, and our general lack of knowledge about them, we need to expand a little more.

I have heard there are differences in the various transmissions used during the production of the TR-6. I do remember some friends, professional mechanics, having to weld in new transmission mounts when changing a transmission on a TR-6. Unfortunately, I do not remember the full conversation and what all was involved. But, one problem which would give you the symptoms you describe, but is not clutch related, would be if the input shaft (first motion shaft) of the transmission was binding in the rear of the crankshaft due to either an overly large (internal diameter) pilot bushing (spigot bushing), or if you had a slightly too long input shaft that was being forced into contact with the rear end of the pilot bushing/crankshaft. At that point, you have direct physical contact with the input shaft and the crankshaft. With the clutch mechanism, you have an indirect contact between the two which may be broken by deactivating the pressure plate to stop the clutch plate from driving the input shaft.

Hope these ideas will be of some use. There are a few people here with TR-6 experience and I expect we will see them posting soon.

Les
Les Bengtson

Íf you put the car in gear (engine not running) and operate the clutch, can your assistants push the car forward? Is the clutch declutching at all?
My bet is that because of the long inactivity the clutch plate rusted against the flywheel.
You might want to try what worked with my MGB: stand on the brakes hard, depress the clutch, engage a gear (I choose 2nd), start engine.
If you are lucky the clutch unfreezes, if your not and panick, you will ram through the garage door. But who cares it's a TR6..... ;-)
Willem van der Veer

Les, the consensus (from your input as well as others)seems to be with the 'stuck clutch syndrome'.
I've been offered a few methods for 'un-sticking'.
I'll let you know how it turns out. Like to try them before removing the trans.

Will, thanx for your method, also. I think I'll leave the door open, tho. (even if it's a triumph, it's still a LBC).
Dennis

Check the travel of the clutch slave piston while someone operates and releases the pedal, should be 1/2" to 5/8". Clutch bleeding can be very difficult on the clutch, the easiest way to to link the clutch and right-hand caliper nipples, open both, and use the brake pedal to reverse bleed the clutch. Empty some of the fluid out of the clutch master first, and don't let the brake master get too low.

If that's OK, then it probably is 'stuck clutch'.
Paul Hunt 2

You havn't used silicone fluid have you?
I bled mine for ages only to get a spongy feel.
Leaving it overnight sorted the problem. The pedal was hard and worked fine.
Dave
D M Tetlow

Just to update;

After trying a couple of different methods to "free a stuck clutch" I came to the conclusion that this clutch really wasn't stuck.
I could drive it up and down the main road basically shifting at the right rpm, and in 4th gear I would depress the clutch pedal, rev the engine then dump the clutch, I could feel it grabbing.
It just wouldn't disengage (or engage?) enough when I was at a stand still to be able to shift.
After swapping out the slave cylinder (just because I had a new spare that came with the car),
and bleeding it a few times, I was still left with the same situation, no clutch!

I remember reading in one of the TR6 restorers manual that the guy had fitted an adjustable push rod at the pedal to the master cylinder to cure his balky clutch problem.
I had already tried lengthening the slave push rod by a bit (didn't have any effect) and trying all three holes in the actuating arm but that didn't help either so it was time to take a look at the MC.
Lo and behold, there were two holes in the fork end of the push rod to the pedal. I had the clevis pin in the first one closest to the master cylinder. Putting it in the last hole or furthest one, instantly gave me more pedal travel and what I was looking for, A CLUTCH!

Boy I feel like an ignoramus (not the first time), the answer was right in front of me.
Thanx for your input guys
Den



Dennis Silance

Blame whoever fitted the non-standard master push-rod is the ignoramus, not yourself.
Paul Hunt 2

This thread was discussed between 16/09/2007 and 23/09/2007

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