Clutch not quite disengaging...

[randall977]

So continues the saga of my non-working clutch...

 

To date I have removed and refitted the gearbox three times. It is an original type TR4 clutch mechanism. Everything in the bell housing is as it should be (I know it all very well now!). The clutch mater cylinder is new and correct, the slave is original refurbished with no air in the system. The slave push rod is the correct length. The play in the slave rod is about 1/2 inch even though it has been adjusted to the very limit (it should be 0.1 inch). I drove the car a short distance last night and the gear changes are VERY crunchy (ie it is not fully disengaging). As the thrust bearing begins to activate the clutch it feels very stiff (but this might be normal for this type of mechanism).

 

The excessive play is where the problem lies but I don't know why - nothing is incorrect or bent (there is excessive wear in the cross shaft but this can only make a small amount of difference). The gearbox is the original. The clutch plate is new - could it be too thick?

 

My next step is to mount the slave on the rear of the gearbox (other side from where it should be) to get rid of the play. If that does not work I will have to remove the gearbox again and replace every component until it works...

[RogerH]

Hi Christian,

as you say it sounds like the play on the slave cylinder is where to start looking,

The actuator rod attaches to the centre hole on the cross shaft lever.

The cylinder normally mounts on the forward side of the attaching plate - will it fit on the rear face of this plate??

The attaching plate is normally on the forward side of the engine/gearbox attachment - will it fit on the rear??

--yes it will I've just looked.

 

Is the slave unit assembled correctly.

Has it been bled corrcetly.

Have you got a return spring on the cross shaft lever

 

Sorry for the ramblings

 

Roger

Edited August 17, 2010 by RogerH

[Steve Priest]

Hi there,

 

Sorry if I'm teaching grandma to suck eggs here.... I'm still getting to grips with my TR4, but just thought I'd share my recent experience after fitting new seals to my clutch slave cylinder. After spending quite some time carefully bleeding the system I thought I'd got all the air out. Took it for a spin and it was almost impossible to get it into gear. Basically I don't think it's possible to bleed the clutch with the slave cylinder in place. The best method I found was to remove the slave and gentle pump the clutch until the piston hits the end stop. Then stand it up so that the bleed nipple is at the very top, open it and slowly push the piston back all the way. Lots of air came out when I did this so I repeated it a second time (after topping up the reservoir). Put it all back together and it worked fine.

 

Steve

[RogerH]

Good point Steve,

if bleeding insitu do make sure the bleed nipple is upper most - otherwise

 

 

Roger

[randall977]

Yes the bleed nipple is extremely difficult to get to - it did improve after the last session of bleeding... I may try and bled it again by removing it - it's better than the alternative! I would say it get 1 inch of movement when I depress the clutch peddle - is that about right?

[Ian Vincent]

Hi Christian,

as you say it sounds like the play on the slave cylinder is where to start looking,

The actuator rod attaches to the centre hole on the cross shaft lever.

The cylinder normally mounts on the forward side of the attaching plate - will it fit on the rear face of this plate??

The attaching plate is normally on the forward side of the engine/gearbox attachment - will it fit on the rear??

 

Is the slave unit assembled correctly.

Has it been bled corrcetly.

Have you got a return spring on the cross shaft lever

 

Sorry for the ramblings

 

Roger

 

 

For what its worth, yes the slave cylinder wil fit on the rear side of the gearbox flange, it just means you need a shortened thrust rod. How do I know this? When I reinstalled the slave cylinder on my TR3a I followed the illustration in the TR2/3 workshop manual which shows the slave cylinder mounted to the rear of the mounting plate (which structurally made better sense anyway) and then spent at least a couple of hours panicking because the thrust rod was too long to fit and had I fitted the clutch mechanism wrongly and would I need to remove the gearbox etc.?

 

It was only after I had checked the action of the clutch mechanism with a scissor jack on its side to confirm that the lever would move and the clutch release - and thought long and hard about hacksawing the end off the thrust rod - that I realised that on a TR3a they moved the slave cylinder to the front side of the mounting plate.

 

Rgds Ian

[TR 2100]

I would say it get 1 inch of movement when I depress the

clutch peddle - is that about right?

 

Easily enough to disengage the clutch.

 

AlanR

[david ferry]

Christian,

 

You are still achieving 0.5" of actual useable slave rod travel.

 

Clearly, this isn't enough.

 

Somehow, you need to get rid of the 0.5" of play in the slave rod.

 

This will improve the action 100% which surely must be enough to disengage the clutch properly.

 

You're almost there.....keep going!

 

David

[randall977]

Thank you for all of the advice - it's very useful! I would say that I am literally a fraction of an inch from sucess - the clutch slips but doesn't fully dis-engage.

 

My actions will be as follows:

 

1. Dismount and bleed slave. Did this work? Yes - sucess. No - go to option 2.

2. Mount the slave on the other side of the bracket to reduce play. Did this work? Yes - sucess. No - go to option 3.

3. Remove gearbox and replace worn cross shaft, replace clutch mechanim. Did this work? Yes - sucess. No - go to option 2.

4. Cry. Did this work? Yes - sucess. No - tough luck!

[david ferry]

Christian,

 

It's good to see that you have not lost your sense of humour!

 

David

[TR 2100]

My actions will be as follows:

 

1. Dismount and bleed slave. Did this work? Yes - sucess. No - go to option 2.

2. Mount the slave on the other side of the bracket to reduce play. Did this work? Yes - sucess. No - go to option 3.

3. Remove gearbox and replace worn cross shaft, replace clutch mechanim. Did this work? Yes - sucess. No - go to option 2.

4. Cry. Did this work? Yes - sucess. No - tough luck!

 

Logical - that would be my approach.

And make sure you have the right end float on the push rod.

 

Hopefully 1. and 2. will sort the problem.

 

AlanR

[Smokey]

Do you have the correct pushrod? My experience with repro parts is that about 50% of them actually work. Do you have the stayrod mounted to the sump? I can't imagine that would allow so much play, but just asking....

[Smokey]

My apologies - I see that you had measured the pushrod .

[randall977]

I've now positioned the slave on the front of the mounting plate so it is nearer to the cross shaft arm. The photo below shows the arm etc in the position when the clutch has not been depressed (so there is 0.1 inch of play - as recommended in the WSM). I haven't been able to test it yet as it needs bleeding but I can see that when the clutch is operated the arm will almost hit the floorpan - is this normal?

 

[had17462]

Hi just seen this topic on your clutch i had a similar problem it turned out to be the wrong thrush race,

nick

[randall977]

Is that the trust bearing? Mine is correct for a TR4 - I did wonder about fitting a later TR4a one (which is deeper) but could be asking for trouble to do that!

[Smokey]

The cross shaft lever is too far back - did it work correctly before? Is the release bearing sleeve the correct length? I've seen so many defective new parts. Once had a stub axle that was machined incorrectly and would not fit.

[randall977]

Yes it does look too far back, though bear in mind it is just about to activate the clutch and so has been adjusted backwards to give 0.1 inch of play. If it is too far back then the only conclusion is that the cross shaft lever has been rewelded in the wrong place for some crazy reason - strange though as it looks original and the WSM shows the relationship of the arm and thrust bearing fork to be as mine seems to be???

[Ade-TR4]

Whereabouts are you?

Maybe someone could have a look-see.

Cheers

Ade

[randall977]

That would be very kind of someone but not much of a day out! I'm think I will battle on with this one on my own and bore you all with regular photos comparing cross shafts etc... What would be really helpful is if someone could look at their clutch operation arm and see if it is in the same position as mine (early type only not 4a type - I'm not suggesting taking the gearbox cover off just a look from beneath)...a photo would be fantastic!

Edited August 18, 2010 by randall977

[Chris Mountford]

Hi again,

 

My advice would be to check that the tapered pin in the clutch fork hasn't broken, they often do, allowing the fork to rotate on the shaft, but only until it bites again on the remains of the pin.

 

Effectively this means you lose the orientation of the fork to the shaft (and of course the drop arm on the end of it). This then gives the symptoms you have - the arm is past the vertical position. In its ''normal'' position the drop arm will normally pass an equal distance through an arc with vertically down being half way. Hope that makes sense ?!?!?!

 

Only way to check for sure is to get the box out again (Aaaaaaargh) withdraw the pin and check that it isn't sheared off. They never shear straight across, but always on an angle which makes them bite again as the fork twists on the shaft.

 

You may be able to tell if you disconnect the operating rod and move the drop arm backwards and forwards and feel it moving on the shaft. If you take it out and it isn't broken, put an additional fixing in it whilst its out because it will break eventually. If it has broken it will always leave the end in place which will stop you pulling the fork off the shaft. So.... drill a pilot hole in the yoke of the fork and drift the broken bit out - fit a new pin to align the assembly and then drill them both and fit the 'additional' fixing.

 

The symptoms you have are very common with these boxes.

 

Hope this helps......and of course this is only my experience.

 

regards,

 

Chris

[randall977]

Thanks Chris. I have already removed and replaced the original broken pin. I put a new one in but slightly bent it during my messing around with the gearbox. I then put in a second new pin and I feel it's unlikely that it has bent or broken yet as I have put everything back correctly (I know this as I have done it three times now!). The play is a mystery and seems to point to a cross shaft / lever arm misalignment but look at the photo - does it look rewelded to you and why would anyone? The cross shaft is pretty hefty - it would be almost impossible to twist or distort. I would really love to see a photo showing the correctly positioned cross shaft lever on a TR4 type clutch...just a quick photo from under the car...

[randall977]

Mind you depending on how worn the clutch plate is the lever will be in different positions. A new clutch plate is thicker so will cause the lever to be further forwards...

[Ian Vincent]

Thanks Chris. I have already removed and replaced the original broken pin. I put a new one in but slightly bent it during my messing around with the gearbox. I then put in a second new pin and I feel it's unlikely that it has bent or broken yet as I have put everything back correctly (I know this as I have done it three times now!). The play is a mystery and seems to point to a cross shaft / lever arm misalignment but look at the photo - does it look rewelded to you and why would anyone? The cross shaft is pretty hefty - it would be almost impossible to twist or distort. I would really love to see a photo showing the correctly positioned cross shaft lever on a TR4 type clutch...just a quick photo from under the car...

 

 

I can do you a photo of my TR3a box and clutch release mechanism from the outside of the bell housing so that you can see the position of the drop arm - I'll post it tonight when I am home.

 

When I rebuilt by mechanism, I obtained an extra strong and slightly oversize pin from Chis Wittor (specialises in saloons), I also drilled a couple of 3mm holes through the release arm/cross shaft and fitted roll pins into them to give some additional support to the main pin. Hopefully it should all hold together and if it doesn't - I seem to recall a recent article in Traction on how to do a concentric thrust mechanism on the cheap (well cheaper than the Revington solution - which I am sure is very good but it is a pricey bit of kit).

 

BTW if you do drill some extra holes in your cross shaft, make sure that they are a reasonable distance from the existing hole to avoid weakening the shaft.

 

Rgds Ian

[randall977]

Hi Ian, thanks for the info. I may have to retract my earlier request for a photo as it won't tell me much unless the clutch plate is almost new... I will try to remedy the situation with my newly positioned slave after which I will just have to bite the bullet and replace the cross shaft and clutch cover mechanism. As the plate wears the situation becomes better regarding the lever arm as it allows the three internal prongs (which the thrust bearing operates) to come out further (in turn pushing the lever arm back).