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gearbox alignment -sticky clutch


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Hi,

 

Suffering from the deaded sticky clutch when hot. Having looked at the forum suspect it might possibly be missalignment of the bellhousing to the engine back plate. I thought there should be 2 x 3/8" "alignment" bolts one at 2 oclock the other at 8 oclock.

However no sign of the thicker 3/8" one at 8 oclock. Nor any sign of the back plate or bell housing ever having a hole large enough to accept this bigger bolt. (although the existing 5/16" bolt is a bit of a sloppy fit). All the holes are the same size accept the 2 oclock one and the starter hole bolts.

 

Should all TR6 have this 8 oclock 3/8" bolt.?

 

Not sure where to go from here.

 

Drill 8 o clock hole to accept a 3.8" bolt. ?

 

Loosen all bolts, nip up again, run engine for a bit, depress clutch a few times, and re tighten bolts in the hope of self-alignment,?

 

 

 

 

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Hello Malcolm, I had a stucky clutch, it was not an alignment problem, but wear on the release bearing carrier. Its a tube of steel that goes over the input shaft to the gearbox. I got a new one from TR Enterprises, and some 'special' grease, and no problem since. It's not easy to see the bolts, nor the alignment studs. I doubt that they are the problem. Gearbox out, I'm afraid. Let us know how you get on. Do NOT drill holes!

Austin

Edited by Austin Branson
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Malcolm,

 

If you don't have any bolts could I take the liberty of suggesting that you buy a set of these

http://www.ebay.co.uk/itm/5-x-3-8-UNF-Bolts-Hex-Head-Cadmium-Plated-Length-1-7-16-Part-NAS6606-14-W10-/162039126427?hash=item25ba48d99b:g:PwoAAOSwnDxUcyZZ

 

They are NAS6606 bolts if you look up the specification you will see that they are certified aviation bolts. They will be exactly the right size, to fit tightly and smoothly, they will not be a loose fit nor over tight. As you believe you have an alignment problem these will put you mind at rest.

 

They are not 3/8 bolts, they are exactly 3/8 bolts!

 

You will not need to drill a hole out they will fit.

 

 

Alan

 

No connection with the seller.

Edited by barkerwilliams
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Hi Malcolm,

I had a sticky clutch on my 4A last summer and it was a pain trying to solve.

 

Eventually I found a very slight wear mark (0,0005") on the underside of the steel tube that holds the bearing carrier.

This was caused by the bearing carrier digging in and causing the 'stickyness'.

This in turn was caused by the above steel tube not being concentric with the splined input shaft of the gearbox.

It was only 0.015" adrift (vertically) but enough to cause utter chaos.

 

I made up a tapered shim to fit under the body of the steel tube to realign the tube/shaft.

 

Roger

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Actually I was in the process of pulling the box out. Got to the point of releasing the lower bolts when I discovered that it appears neither the bell housing or the back plate ever had a 3/8" alignment bolt at 8 oclock. And without drilling out existing hole would not ever take this "larger" size bolt.

 

Then remembered reading that missalignment might cause the stckyness. ( I dont quite understand why, but there we are)

 

Think I might try a bit of readjustment of alignment before struggling to remove the box completely.

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Malcolm,

 

On my gearbox the "correct" holes are not much larger than the smaller ones. The smaller bolts have a hole slightly larger than the bolt so fixing bolts fit easily with fingers and have play. The two alignment bolt holes are a tight fit and may need to be, I think the term is drifted in, not hammered just eased with the gentle assistance of a hammer.

 

So that when it is in there is absolutely no lateral movement at all, not even a nats.

 

The holes are not as large as you would expect for a "normal" 3/8 bolt, after all it has an alignment purpose.

 

Alan

Edited by barkerwilliams
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Hi Malcolm,

the stickyness can be caused by a misalignment of the bellhousing to block.

 

The bearing carrier and clutch cover need to be well aligned.

if the steel tube that has the bearing carrier sliding on it is out of alignment then the following happens.

 

The release bearing is pushed forward onto the clutch cover fingers.

The fingers become concave and the release bearing is convex.

The bearing sits inside the concave fingers - the problem is the concave fingers are on the centreline of the crank but the gearbox isn't.

When the clutch pedal is lifted the release bearing tries to come back inline with the engine/gearbox but because the gearbox is not aligned

it allows the carrier to cock slightly to get back to it's previous position - eventually the carrier will start to dig into (8 weeks in my case) the steel tube the carrier slides on.

When it digs in pressure is removed from the release bearing (the slave cylinder is returning to its off position). However it doesn't stay there long and the release bearing tries to catch up with the footpedal etc and it all goes bang.

 

Roger

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I learned that if British engineers use alignment bolts

they are necessary.

I had endless discussions with people who lost these bolts

when repairing customers clutches.

 

I am sure there are many other reasons that the clutch

is a bit sticky but why talking and talking when the remedy

is that easy and buying and fitting these bolts costs a few cents?

 

When the bolts are fitted one can be sure that one reason to stick

is solved and for me thats worth much more than the few pence for the bolts.

 

As these bolts are often gone I make my own on the lathe cutting a M10

down to proper size. It looses a bit from the thread but still can be used..

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If you need a dowel bolt to make sure this is the problem first of all then take two out of any of the prop flanges to use to get the box aligned for the minute then replace your prop bolts as they have the correct amount of shoulder. I can assure you that the hole at 8 o`clock is the correct size it will just have crud in it.

Stuart.

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Or is it a duff release bearing - causing the bearing carrier to get hot and stick on the extension?

 

This phenomenon didn't used to happen until the past few years and has become less common recently. That begs the question as to why?

Presumably bell housing to engine plate misalignments have existed since the cars were new (ish) so not convinced by that theory.

Slightly worn bearing carriers again is unconvincing - a bit of wear should increase clearance so is this a convincing cause for the carrier sticking?

 

There are bearings that are poor quality, run hot in contact with the clutch and then get hot and transfer the heat to the carrier which expands and takes up the clearance.

 

What soled the problem? A new bronze carrier, special grease or a good new bearing? My money is on the latter but the first two will help as will correctly aligning the gearbox.

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Starter motor bolts will work too. The easiest solution is to slacken every bolt, remove the offending 9/16" bolts occupying the 3/8" holes and fit 3/8" bolts or a pair of 3/8" drill bits. Once you get these in ( you'll have to wrestle the gearbox until they go through ) you can tighten the rest of the bolts, withdraw the bits and put whatever you want in. As Roger indicated, 0.015" is enough to cause trouble; this is roughly half of the clearance provided for the 5/16" bolts, so without dowels of some sort the g'box just drops that amount. Regular 3/8" bolts will work OK but precise ones will give a more, well, precise result.

 

You can also use any intact pair of opposing holes and fit 11/32" bits through them. This is what I did before I learned of the (2) 3/8" holes. Told TRIUMPH WORLD about it and got a free subscription back in the 1900s.

 

Offset gearbox installations have sold innumerable " fixes " for TR clutches; hydraulic throwout mechanisms, belt and suspender throwout fork fastening, etc. This because the t/o bearing always tries to find the centre of rotation ( crankshaft centre ) upon engagement and when this is different than that of the gearbox snout it will drag thereon, guaranteed.

 

Cheers,

Tom

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Offset gearbox installations have sold innumerable " fixes " for TR clutches; hydraulic throwout mechanisms, belt and suspender throw out fork fastening, etc. This because the t/o bearing always tries to find the centre of rotation ( crankshaft centre ) upon engagement and when this is different than that of the gearbox snout it will drag thereon, guaranteed.

 

Cheers,

Tom

Hi Tom,

that was also my conclusion. However it is not the dragging whilst engaging the clutch but the carrier digging in on clutch release.

Any wear in the carrier ID would make things worse.

 

Regarding the misalignment of my bearing carrier tube to splined input shaft.

I set the carrier tube casting up on my lathe and checked it out with a DTI and it was in all effect perfect - everything round, square or in-line.

The splined shaft is fixed by the front bearing and its end bearing - these are seriously fixed in place.

It should also be square to the front face of the gearbox (where it comes out through the bearing) -but it wasn't

 

To check the eccentricity I turned up a simple ring 1" long x ID=splined shaft OD x OD= OD of steel tube

It was perfect at the 9 & 6-o-clock positions but 0.015" out vertically

 

Roger

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Been idling following this thread and wondering why its never reported as a problem on the Vitesse and GT6 given that the engine block is identical, the engine mounting plate is the same(ish) and the clutch cover plate is the same, and whilst the Vitesse and GT6 do have a single locating dowel for the gearbox at about 1min past 12 all it really does is ensure that you have the gearbox and engine rotationally aligned rather than square. About the only major differences are that the Vitesse and GT6 use a brass/bronze bearing carrier and the actuating arm is a floppy arm that pivots on a ball headed pin.

 

Its almost like the TR mechanism is all too fixed so the slightest alignment issue causes problems, whereas the release mechanism on the Vitesse and GT6 I think just adapts to virtually any angle it encounters and pushes squarely on the pressure plate. Never seen any wear on the inside of the bearing carrier either.

 

This was about the only shot I could find of the release mechanism.

 

http://www.rimmerbros.co.uk/Item--i-GRID007802

 

Alan

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I rebuilt my clutch assembly last year with the following: AP clutch + Bearing, Revington genuine bronze carrier ( not brass, as some?), Saloon bearing carrier slippers, oil-lite cross shaft bearings, the fork additionally pinned to cross shaft.

 

Result: no sticky clutch or ratcheting!!!!! I fact the clutch has never worked as well even when the car was new? Its just one smooth in and out operation! Tested in M4 traffic jam of 3/4 of an hour!

 

But I also had the gear box/O/D rebuilt which had all new bearings etc. was 43 years old and never been rebuilt. The engine was re-built, I was talked into a fully balanced bottom end and some parts were lightened, some parts were miles out of balance, as shown on their m/c. The end result was an engine that is turbine smooth and ticks over in a different league to what it ever use to?

I now wonder if this also has an effect on the clutch operation, especially if the flywheel was out of balance as much as mine?

 

Bruce.

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