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Clutch won't disengage on T-54

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We have a T-54 that was running well, and then suddenly the clutch would not disengage. In other words, when the clutch pedal is pushed to the floor, we cannot select any gear. There is just the grinding of gear teeth.

 

Pressure plate lift in the clutch when all was well was about 8 mm, so in spec. After the problem started, pressure plate lift was found to have reduced to only 4 mm. Adjusting pedal free play and total travel got pressure plate lift back to 9 mm, so it seems the linkage between the pedal and the pressure plate is working OK. But gears still grind and no gear can be selected. The problem appears to be internal to the clutch.

 

Anyone seen this before?

 

Also, it looks like the gearbox must come out to allow removal of the clutch. Can anyone confirm?

 

Malcolm

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That sounds like the friction plate has become rusted stuck to the flywheel so is still turning the gearbox input shaft. I used to come across this occasionally on vintage vehicles I used to work on. The solution with those was to engage a gear, and then start the engine with the clutch pedal depressed, the vehicle would lurch forward, then the friction plate would free off (sometimes with a bang). However, I wouldn't recommend this with something as large as a T-54 unless you have a lot of space in front and can guarantee the engine can be shut off if the clutch friction plate didn't disengage; you have a runaway vehicle and the results could be disastrous.

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stolly clutch does it all the time if you leave it engaged, very annoying...I had one that was very very stuck after water got in for a week. I put coke on it that helps free up some of the rusty bits, tried a bit of very carefully pointed WD 40 and after about 6 months of fiddling we got it freed.

 

 

can you get any access to the clutch plates, can you see if they are moving, are there two plates or a single one, the stolly has two and its the one nearest the engine that sticks, well it was with our one...dont know if that helps but it does sound like the same problem...

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Have seen this before when the T-54/5's are left in gear and allowed to sit, did the tank sit all winter?

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This is a multiplate clutch with around 10 friction plates and 9 steel disks. You can see the pressure plate move through a small access hole but you can't see the plates.

 

We tried starting the tank in gear. It lurched forward and stalled. The clutch is well and truly locked. We don't want to try it again because of the load on the starter and drive train, and the potential for doing more damage to the clutch.

 

This didn't happen after a period of storage. It happened over a day. It ran fine one day and then as it was being parked, the gear shifting was getting harder. The next day, when it was started, the clutch was locked up enough that none of the gears could be selected.

 

This is not a standard clutch in a bell housing with the flywheel bolted to the end of the crankshaft, and the pressure plate bolted to the flywheel. It's a "free-standing" clutch, as it were, supported on one side by the gearbox, and with the other side connected to a transfer case by a flexible gear coupling.

 

Looks like we will have to pull the gearbox to get the clutch out. Just wondered if anyone could confirm that.

 

Malcolm

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can you get any access to the clutch plates, can you see if they are moving, are there two plates or a single one, the stolly has two and its the one nearest the engine that sticks, well it was with our one...dont know if that helps but it does sound like the same problem...

 

Paul,

Back in the days when Stalwart was still in service, there was an instruction to use ceramic clutch plates, they were available to demand through the stores system. These plates did not absorb moisture like an asbestos type material and therefore did not stick. I have used them and they do work fine.

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Malcolm I have an English manual for T54 series, I will check it tonight, our entire drivetrain is out of our T69 but I believe clutch can be removed on its own. Is it possible it is stuck in gear and the problem is in the transmission?

 

John

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John, the gearbox is in neutral right now. With the engine running, it won't go into any gear. It just grinds as the gear lever is pushed into each gate position. But with the engine shutdown, it will go into any gear. So no, it doesn't appear to be the gearbox.

 

We have an English translation of the basic in-the-field type maintenance manual but have nothing on actual disassembly and repair of individual components like clutch, gearbox, etc. Any info you have on this would be a big help!

 

I had another look today. There's no way the clutch can be removed on its own. We'll have to pull the starter and the gearbox. I just hope the gear couplings between the gearbox and the steering gears/brakes will pull back far enough that those don't need to be removed. This photo isn't great but it shows the clutch with the ring gear on the OD.

 

Malcolm

 

DSC00142.jpg

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Ok, the two sliding couplings that connect the gearbox and steering clutches will for sure slide back enough to allow gearbox removal, I have recently done that job myself. I can take some pictures of our engine clutch setup on Saturday if that helps, is there no sliding coupler between the clutch and transfer case?

Edited by jdmcm

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Man I forgot just how packed that engine bay is with everything in place, she's crammed!

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OK, that's good news that the couplings between the gearbox and the steering drums will slide back far enough to allow gearbox removal.

 

Yes, there's a coupling between the clutch and the transfer case, so based on the steering couplings it should also slide back towards the t/c enough to clear the clutch. But there is no coupling between the clutch and the gearbox, so it seems the gearbox and clutch will have to come out as one assembly.

 

It doesn't look like that is a really big deal. The engine/gearbox covers will have to come off. And the rad, the oil cooler, and the starter. And then I'm sure the gearbox will just lift straight out, right? :)

 

Thanks for your insight, John. Any photos would be greatly appreciated. Are you pulling the clutch apart?

 

Malcolm

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I took a bunch of photos this weekend, will post them tomorrow, clutch is attached to the transmission and then to the transfer case with a sliding coupling. Once you have the rad out and oil cooler out you will be able to remove the air cleaner box and bracket, this will allow you to disconnect the engine from the transfer case and the clutch from the transfer case. The transfer case has a unique mounting, the bolts closest to the left side of the hull are 32mm bolts which are threaded into the mounts so they will come out relatively easy from the top, the other two are actually installed from the bottom of the transfer case with nuts and cotter pins on top. Remove the cotter pins and nuts and you will have to drive the two bolts down through the transfer case and mount. This will take some effort as they have a machined shank which helps locate and align the transfer case, be aware of the location of the shims which are likely to be under the transfer case. With the whole rear engine deck removed this box will pretty much lift straight out, hope this helps. And yes we are installing a new engine and have taken the opportunity to clean up the years of oil and diesel sludge in the hull of the tank...it's a mess....and on that note, be very careful using a torch in the engine bay...that oil diesel slurry will catch fire and the garden hose won't put it out...

Edited by jdmcm

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John, I was puzzled by your post as the clutch is between the transfer case and the gearbox, not the t/c and the engine. And then I realized you think I'm asking about a T54. In fact I'm asking about a Russian T-54!

 

Anyway, it's turning out to be quite a straightforward job, and it's progressing steadily.

 

Malcolm

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Hi Malcolm

 

yes sorry, I re-read what I wrote and went back and fixed it, clutch is indeed between transmission and transfer case, what we did was remove the transfer case which allowed access to remove the clutch while leaving both engine and transmission in place, this way you don't have to disconnect the transmission control rods, fan drive, air compressor etc., but removing the transmission would take the clutch with it as well and give a great opportunity to clean out the accumulated fuel-oil-dirt mess. Ours is a Chinese Type-69 captured in Iraq during the Gulf War, same drive-train as the T-54. Does yours have the hydro-boost assist for the clutch and steering? Sometimes this can cause grief as well...but my guess is you have had a spring failure inside the main clutch...very curious to see what you find once you have it open, please keep me posted, not so many of these girls in Canada

 

 

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Edited by jdmcm

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John, that's interesting, pulling the t/c so you can pull the clutch off the gearbox input shaft. Never thought of doing it that way. But we're committed now. It gives us a chance to inspect the very noisy fan drive, lube the brake, steering, and clutch linkages and shafts on the hull (all mechanical, no hydraulics), and replace some dodgy hoses, as well as cleaning up the 1" deep sludge as you mentioned.

 

I'll let you know what we find.

 

Malcolm

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The noisy fan drive is virtually normal. If there is nothing actually failed it is caused by excess backlash in the gears. There is provision for setting this but no one ever seems to bother. I was seriously looking at getting a VT55 a couple of years ago and was warned that the clutches will not put up with more than the minimum period disengaged without the residual drag making the plates get hot and warp. That causes more heating and warping untill it is impossible to get it into gear. If yours has suddenly got much worse it is not impossible that a plate has split and the ends have overlapped, removing any clearance that was available.

 

Good luck, David

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David,

Regarding the fan drive noise, we have member here who worked on these tanks in Romania, and, like you, he says don't worry, it's normal. But the noise is scary. People back away from the tank when it starts! Keeping the idle rpm above 750 helps a lot.

 

I have what looks like quite an elaborate procedure in a Russian manual for checking the fan drive but translating it is painful. And I suspect the outcome is, if clearances are excessive, the fix is to replace worn parts. Or is there an adjustment of some kind? Do you know what the gist of this procedure is?

 

Yes, the plates are a major suspect here, especially as pressure plate axial movement when the pedal is depressed dropped from around 9 mm to 4 mm after the clutch locked up. (The spec is 7-9 mm.)

 

Malcolm

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I have a spare clutch that has been disassembled, I will try to post some pictures in the next day or so. Unlike a truck clutch, they do not seem to tolerate excess slipping, it is not uncommon to see these tanks lurch forward when the clutch is released. Is this a cause of improper adjustment or simply a characteristic of the design? David can you weigh in on this?

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On the subject of fan noise, once your transmission is out you can thoroughly check the fan for damaged blades or areas of the fan surround that are coming into contact with the fan. On the Type 69 we have the fan is much larger than the T-54 as the Chinese copied the large fan of the T-62/64 family. Lots of tanks have the hinged panel on the right rear hull missing which allows debris to fall directly into the fan intake and can wreak havoc on the fan blades/vanes.

 

Malcolm where did your T-54 come from? Is it actual Russian manufacture or Polish or Czech? I am assuming it is the one at the Ontario Regiment Collection? Would love to know the history of it. We have been able to trace ours back to within days of its capture in 2003.

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OK guys, you force me to actualy look in the manuals !

 

Fan noise: As I said before the main cause of this is backlash in the gear drive combined with an enormous fan that has a very large rotating mass and no provision to damp the surges in the drive as the free play is taken up. As such it is a pretty unsophisticated design (suprise) but seems to keep working anyway. It would certainly be possible to add shims to reduce the backlash in the bevel gears but I suspect that that was not the intention of the designers. There will also be backlash in the gear set before the bevel gears and I don't think it would be possible to do anything about that. If there were a coupling with a lot of rubber in it to cushion the drive it would make a huge difference but it is hard to see how to fit one. There is an overload clutch as part of the fan hub but that is not much help here, it just stops shaft breakage if the fan jams.

 

Main Clutch: As you know this is built up onto the main gearbox and would normaly be removed with the main gearbox. It does not come off as a unit but in lots of bits. It seems that it was not designed to be other than fully engaged or disengaged. If you slip it, the plates get very warm very quickly and warp, making it impossible to disengage. This is really poor design by our standards but they have made a lot of them over many years. It is expected to transmit a great deal of torque and does so at a very basic level. You just need to revise your expectations !

 

I strongly suspect that the clutch that triggered this thread has one or more plates that have damaged themselves but you will only find out when you get it apart. It is possible that the release mechanism has a problem as it is very unlikely that it has ever been greased and something might have frozen or broken up.

 

As I said before, Good luck !

 

David

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On the subject of fan noise, once your transmission is out you can thoroughly check the fan for damaged blades or areas of the fan surround that are coming into contact with the fan. On the Type 69 we have the fan is much larger than the T-54 as the Chinese copied the large fan of the T-62/64 family. Lots of tanks have the hinged panel on the right rear hull missing which allows debris to fall directly into the fan intake and can wreak havoc on the fan blades/vanes.

 

Malcolm where did your T-54 come from? Is it actual Russian manufacture or Polish or Czech? I am assuming it is the one at the Ontario Regiment Collection? Would love to know the history of it. We have been able to trace ours back to within days of its capture in 2003.

 

John, no damage to the fan or shrouding. The noise is just as David says, backlash in the drive. The massive fan impeller at the end of the long, spindly drive shaft appear to have a torsional resonance below 750 engine rpm, which oscillates it backwards and forwards, reversing the load on the drive gears.

 

Yes, it's at the Ontario Regimental Museum. It came from the Littlefield collection in the States. I think it was built in Czechoslovakia. It's a bit rough but after we recently freed up the seized gear shift, brake, and steering linkages, it was running very well, and was popular in our "Tank Days".

 

Malcolm

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Malcolm here are few pictures of the clutch guts, you can see the friction disks (all ground steel) and the driven disks.

 

IMG_20160623_163619.jpg

 

Also on our Type 69 there is a clutch in the blower fan hub itself which will protect the fan drive from shock in the case of sudden RPM change or debris jamming the fan itself. After you set up the drive gears you could check that if it is still noisy. Not sure if the T 54 has that feature or not. That was a very nice tank as I recall and in great shape inside, I believe it was imported and owned by Greg Taylor, the head restoration guru at the Littlefield collection, great acquisition!

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John, thanks for the photos.

 

The drive drum on our clutch doesn't have the two large cut-outs at 180 degrees that yours has. I wonder if that was an attempt to improve cooling?

 

From the drawings I have, the friction disks have the teeth on the OD and the steel driven disks have the teeth on the ID. I can't see any friction material on the friction disks in your photos. Is it all worn off or just covered in rust transferred from the steel disks?

 

Malcolm

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Malcolm

 

those steel disks are the friction material, page 390, para 5 of the manual states:

 

" like the drive discs, the driven friction disks are steel with ground friction surfaces. The drive discs have external teeth and the driven discs have internal teeth"

 

In our clutch that is it, there is no conventional friction material like you see on the clutch of a car or truck. Very interested once you get yours open to see if it is any different but I suspect it is not. In our clutch we have ten steel driving discs and nine steel driven discs for a total of 19 discs (up from the previous models which had 17). You can see why when the tank sits and there is moisture in the engine bay how the clutch plates can become frozen together, I realize that is not your issue but it can and does happen.

 

John

Edited by jdmcm

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According to the manual the two large cut outs are designed to allow both moisture and debris out of the confines of the clutch pack. This started with the Type 69 like ours, it is also evident on the Type 69 at Marine Corp Base (MCB) Camp Pendleton. I have also seen this on various T-55's.

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