Gearchange problems

[PLTR6]

Hi, I’d appreciate some advice on my 1970 TR6 clutch problems..........

I rebuilt my TR6 over lockdown. ‘New’ chassis and body, swapping the engine and box over from one chassis to the other without doing anything major to them because they were working perfectly, and they have been undisturbed for at least 24 years with fairly limited mileage.

My first big drive was to Malvern last year when I found getting into 2nd gear difficult, especially going down from 3rd .

Since then it has been getting progressively worse, to the point where it is no fun driving it. I’ve tried a few fixes but no joy.  The symptoms are:

·        Engine off I can get all the gears. Not Ford smooth, but doable.

·        Starting from cold, gears are gettable, but reverse grinds horribly.

·        As the car warms up it becomes harder and harder to find all gears, especially 1st and 2nd and reverse but then I get nasty grinding on 3rd.  Double declutching and slowing the engine revs can help, but not always.

·        Eventually I have to force it into 1st or 2nd to get going, and that isn’t easy. One day I really will get stuck at a junction. Quite stressful.

·        If I am stationary and get it into gear there is no creeping forward or change in revs.

·        Driving along there is no clutch slippage.

·        Overdrive works fine

 

What have I looked at so far?

·        I have bled and bled the clutch, including holding the bleed valve vertical as in other posts.

·        I have taken the slack out of the linkage, so there is minimal slop at the pedals and the clutch cylinder. The pedal box has new bushes.

·        I’ve measured the movement in the rod at the slave cylinder, 17mm which seems ok according to the forums.

·        I disconnected that rod and checked for ‘slop’ and it feels pretty tight, hanging vertically.

·        I’ve topped up the gearbox with oil....there is a slight leak but not that much.

·        When I rebuilt the car I refurbed the master cylinder with new seals.  It is a .70” version.

 

What next?

I really want to exhaust all possibilities before I take the plunge and take the gearbox out.  I am aware of weaknesses inside the clutch, especially the fork pin, and maybe the synchromesh is the problem?.  If the forum’s advice points there, so be it, but this is one last try to avoid it!  Thanks in advance.....

[stuart]

Did you fit the dowel bolts to the gearbox/engine.

Stuart.

[PLTR6]

Hi Stuart, I didn't split the engine/gearbox, just moved from one chassis to another, so I didn't remove the dowels.  I assume they are fitted!

Thanks

[RogerH]

Hi,

I would assume nothing, many owners do not appreciate what the two dowel bolts do.

 

Easy to check.

 

Roger

Edited July 16, 2022 by RogerH

[PLTR6]

3 hours ago, RogerH said:

Hi,

I would assume nothing, many owners do not appreciate what the two dowel bolts do.

 

East to check.

 

Roger

Thanks Roger.  I've had a look and while it looks like bolts in those positions (2 and 8 o'clock) they do look different to the other bolts fitted.  Is this what I am looking for?  And given the box performed without a fault for 20 years up until the chassis change, would this still be a likely cause? Regards, Paul

[RogerH]

Hi Paul,

they sound like you found them.

Indeed after 20 years the evidence suggests they were not the problem.

I take it you have oil in the box

Roger

[PLTR6]

43 minutes ago, RogerH said:

Hi Paul,

they sound like you found them.

Indeed after 20 years the evidence suggests they were not the problem.

I take it you have oil in the box

Roger

Yes, I changed the oil when I had good access with the body off.  Probably the first time in a while because the filler plug was badly rounded and a sod to remove.  I have checked the levels since.

 

[Chris59]

Wrong grade of oil or quantity, eventually. An overdrive can take a moment to be at the right level.

[John L]

Slave cylinder push rod should be in the middle of the 3 holes in the clutch arm,

Is there anything that could be stopping the pedal going fully down, ie carpet or padding?

The clutch slave bleed should be at the top, when bleeding try and get the pushrod fully into the slave body, and see if you can clamp it in that position, then bleed the slave,

Have you tried depressing the pedal down fully and blocking the pedal with a wood bar against the front of the seat and leave overnight, and then release slowly, it works when you need to get the last air out of brake systems so may well work here, worth a try at least!

John 

[PLTR6]

14 hours ago, John L said:

Slave cylinder push rod should be in the middle of the 3 holes in the clutch arm,

Is there anything that could be stopping the pedal going fully down, ie carpet or padding?

The clutch slave bleed should be at the top, when bleeding try and get the pushrod fully into the slave body, and see if you can clamp it in that position, then bleed the slave,

Have you tried depressing the pedal down fully and blocking the pedal with a wood bar against the front of the seat and leave overnight, and then release slowly, it works when you need to get the last air out of brake systems so may well work here, worth a try at least!

John 

Thanks John,

The push rod is in the middle hole and the pedal is hitting metal at the end of its travel.......I peeled back the carpet just to be sure!

I'll try that bleeding trick. One question though.....given I am getting 16/17mm of travel in the pushrod, which seems to be the target in the forums, would better bleeding (if I can get it) help?

Regards

Paul

[PLTR6]

14 hours ago, Chris59 said:

Wrong grade of oil or quantity, eventually. An overdrive can take a moment to be at the right level.

Thanks Chris,

I'm using Penrite GB40 which seems to be well recommended. Would you agree?  I filled it when I had he body off and then rechecked it via the side filler until it started to drip out, left it a while, rechecked and sealed it up.

Regards

Paul

[BlueTR3A-5EKT]

Crankshaft thrust washer end float? 

Have you checked the crank does not have excessive end float?

Easy check - push and pull the front of the crank with a lever  If you can see movement it is too much as the spec is quite small  4-6 thou I think.

Peter W

[PLTR6]

33 minutes ago, BlueTR3A-5EKT said:

Crankshaft thrust washer end float? 

Have you checked the crank does not have excessive end float?

Easy check - push and pull the front of the crank with a lever  If you can see movement it is too much as the spec is quite small  4-6 thou I think.

Peter W

Thanks Peter,

I just had a good push and pull and couldn't feel or see any movement....which is a relief as I didn't fancy that job as well!

Regards

Paul

[BlueTR3A-5EKT]

54 minutes ago, PLTR6 said:

Thanks Peter,

I just had a good push and pull and couldn't feel or see any movement....which is a relief as I didn't fancy that job as well!

Regards

Paul

Good news.

You would hear a clonk as you pushed from front to rear if the float was excessive.

Peter W

Edited July 17, 2022 by BlueTR3A-5EKT

[John L]

It could still be that the thrust bearing is not pushing on the fingers squarely, and so the cover is still touching the plate on one side, I have seen sometimes the pins in the fork wear on one side and so the fork doesn't push the carrier squarely to the fingers, also if there is a pin in the carrier to stop it rotating, sometimes the fork finger wear a groove there, leading to the carrier not pushing square.

It may also be oil on the clutch plate, which is dragging against the flywheel or the cover, you could try slipping the clutch a bit to see it polishes the plate and allowing it to be freer.

John

[Chris59]

3 hours ago, PLTR6 said:

Thanks Chris,

I'm using Penrite GB40 which seems to be well recommended. Would you agree?  I filled it when I had he body off and then rechecked it via the side filler until it started to drip out, left it a while, rechecked and sealed it up.

Regards

Paul

80w90 GL4 in my TR2 to TR6 manual gearboxes.

IMHO, the point that the problem is related to temperature is important, and disqualify worn thrust washers.

[SeidelVC69]

I`m afraid its the fork pin, as is in so many other cases. Dieter

[PLTR6]

Thanks for all the comments.......it looks like I've tried everything up to opening up the clutch & gearbox so that will come next, but I'll leave that for freezing winter nights. Meanwhile, it's back to the ever reliable MX5

[PLTR6]

Hi All, Can I restart this thread....still struggling a little!

The general advice was that the clutch fork pin must have sheared, and having tried/tightened/bled everything else I took the plunge and removed the gearbox.  Of course, the pin is pristine!

So now I have the box out.....what should I do while it is out. 

Should I replace the pin anyway, if so where do I get a high quality hardened item?

Should I replace the clutch? The incumbent has been there since around 1990 with light use, but is not a brand I can identify. It is 'Made in Great Britain' and coded QY13039 on the pressure plate and KC2403 on the fingers.  Any recommendations on a replacement?

And given it isn't the pin, or the movement at the slave, or slop in the linkage, or the oil used, or the dowels, or the end float, and given the gearbox seems pretty smoooth without the annoyance of a clutch fitted, does anyone have any more ideas on the root cause of a really hard to use gearbox?

All thoughts welcomed!

Many Thanks

Paul

[stuart]

First of all cross pin the release fork, check the pins on the fork arent worn, if so replace or if its not already been done rotate through 90 degrees.Check that the nose cover is the correct one as the earlier one is too long, check that you have the correct release bearing fitted and that it slides smoothly on the nose cover. I does seem as if the wear on the fingers of the cover isnt even either.

Stuart.

[PLTR6]

Thanks Stuart......better picture of fingers attached, it looks even to me but I'm no expert.   I'm not sure what you mean by nose cover, but it and the release bearing have been in situ for a long time, until i switched chassis.

I will do the cross pin mod.....I don't want to take the box out again!

Regards

Paul

[RogerH]

Hi Paul,

see item # 10.  NOSE

 

Roger

[stuart]

A smear of copperslip on the nose shaft might not go amiss too.

Stuart.

[PLTR6]

Thank You Roger and Stuart

The Nose measures 51mm, fairly dead on 2".  Moss and Rimmer say it mustn't exceed 2", and refers to the 2 3/8" earlier version so I'm thinking I'm OK.

 

Any recommendations on the right/best new clutch available currently?  The forum does seem to have a few bad experiences.......

[ntc]

For starters the forks are not central remove nose cone and check it’s flat to the gearbox secondly check the sleeves in the bell housing are they worn?