Welcome to our resource for MG Car Information.
MG TD TF 1500 - Clutch Release Problem
|This last week has just been a ton of fun. When I havenít been rummaging in the musty archives looking for possible answers to my problem, I have been removing and replacing my TDís gearbox trying to diagnose the problem, but now I need your help!|
My newly rebuilt engine is running well, but when I tried to make that first ceremonial drive to the end of my driveway, all I got were grinding gears when I tried to put it in 1st gear, and it wouldnít go into any other gear either, as though the clutch wouldnít release. I have a new clutch disc, throwout bearing, and all the linkage has either been refurbished or replaced, so itís good and tight. The lever has the O'Connor modification. The pressure plate and flywheel are in good condition and have no rust or moisture. Depressing the clutch while in gear and with my son pushing the car only resulted in turning over the engine. Given the number of delicate and pricey parts involved (tranny gears, crankshaft, axle half shafts, etc.) I was reluctant to start it in gear with the clutch pedal depressed, and so, knowing how to have a good time, I elected to remove the gearbox with the engine still in the car in order to have a look at the clutch. I had a devil of a time separating the bell housing from the engine. Everything looked ok when I finally got it apart, but when putting it back together I had another devil of a time getting the engine and bell housing close enough to put the bolts back in. I donít remember if it was difficult to put it together the first time, but that was a few months ago and the engine and tranny were out of the car and a whole lot easier to work on.
The only thing I can think of that may be causing my problem is that the first motion shaft is too tight a fit in the new pilot bushing and so the gearbox stays engaged even if the clutch is released. Is that a reasonable diagnosis? If so, what options do I have to correct it? Are there other possible sources of trouble?
Thanks for any help you give. Iím still hoping to make that ceremonial 50 foot drive out to the street soon.
Did you put the clutch friction plate in the correct way round? Did you use an alignment tool to line the plate splines with the spigot bush? The exhaust manifold studs fit into the bell housing screw holes and can assist when you are refitting the gearbox. Please let us know how you get on.
I'm with Jan on this one,,,,there should be an indicator on the clutch disk "this side towards engine" (or flywheel)
Your linkage is just way out of adjustment,,, Why did you replace the linkage??
|When you operate the clutch,, can you see movement of the complete linkage?|
Be aware that on these cars, excessive clutch peddle movement will result in the pressure plate re-engaging the clutch disc in an unattended fashion. What happens, is the back side of the 3 pressure release arms contacts the clutch disc and re-engages it. Your problem could be too much clutch peddle travel There is a touch stop mechanism in the peddle box to limit its travel. I am very knowledgeable in these cars and if you would like to call me, I will help you.
|With all aligned correctly, the tranny/bellhousing should slide right in without any bind. The only way to tell if it is the bushing is to remove the clutch and then see if it slides in and/or is still stuck/binding. The suggestions above are all good also. George|
Welcome to the Forum!!!! Your knowledge will be greatly appreciated !!
I have heard that this can happen with the O Conor mod, try to go back to the original setup and see if that works. To see if the clutch frees up you can use the starting handle. remove the spark plugs, get somebody to engage a gear, then with the clutch depressed try turning the engine over with the handle.
|Thanks for all your suggestions. I didn't think to try to slide the gearbox in without the clutch in place, but I'm quite confident the components are installed and centered correctly. The binding started about where I guessed the first motion shaft entered the pilot bushing, which is why I suspected the problem is a too-tight fit there. |
The clutch plate is facing the right direction--I double checked that as my first thought was maybe it was installed backwards the first time (it wasn't). I used a pair of exhaust manifold studs to guide the removal and installation of the gearbox, and I used a clutch installation tool to center the disc.I replaced the linkage because it was worn and sloppy. It seems to be working correctly now. With a mirror and some body contortions, I can look in the inspection hole and see that the throwout bearing seems to move ok.
Gregory, I'm going to check the linkage adjustment once again, and I may be giving you a call.
John, I'll try your suggestions.
|Joe, I've been thru that myself. Turns out that I had inadvertently 'mushroomed' the pilot bushing and it had a firm grip on the first motion shaft. Bud|
|"There is a touch stop mechanism in the peddle box to limit its travel."|
Gregory is correct about the stop bolt needing to be in the pedal box to limit the travel of the clutch rod and the throwout bearing. That said, the clutch stop bolt was not incorporated in the TDs until car number TD22251. Cars prior to TD22251 started life with a cable operated clutch linkage, which had a different clutch stop arrangement. If/when the cable linkage was replaced sometime in the past with the rod linkage, the stop bolt will not have been installed in the pedal box and it will be necessary to fabricate one to install. See the article "Clutch stop in pedal box" in Bud Kruges's Ttalk at: http://www.ttalk.info/Tech/TechIndex.html Cheers - Dave
|D W DuBois|
At this point that sounds like the most likely cause of the problem. How did you correct it? If I replace the pilot bushing, how do I make sure that I don't just screw it up again? And, can I do it with the engine still in place?
|Sorry, Joe. You have the get the gearbox out of the way to remove the spigot bushing. Best way that I found was to get a piece of wooden dowel the diameter of the gearbox shaft. Poke grease into the present bushing. Slip the wooden dowel into the bushing and give it a good whack with a hammer. Bless that law of physics that controls pressure in a fluid. The pressure from the hammer whack will drive the bushing out of the recess in the driveshaft. Just be a bit more careful when you install the new one. Good luck. Bud|
|Thanks Bud. I understand that the gearbox has to be out of the way, but can I remove and install the bushing without removing the engine too? Do you think the mushrooming happens when installing the bushing itself or when installing the gearbox? Sounds like I'm in for more fun in any case.|
|joe, more than likely, if the spigot bushing is mushroomed, it was damaged when you installed it..neither the flywheel nor the engine has to come out to remove the spigot bushing. |
did you use a clutch alignment tool when assembling the clutch?..if so you can use that or a spare input shaft to check the bushing I.D. prior to removal. regards, tom
|Joe, I'm sure that you can do it without having to re4move the engine, just the gearbox. The term 'mushroomed' is backasswards. The end of the bushing was driven inwards such that the motion shaft could be forced through it. It was obviously something that I did while installing it. Funny thing is that I kept the old bushing on top of my desk until I tossed it out a couple of months ago. The dowel/grease/hammer technique will remove it without distorting it. You'll be able to see how it deformed. |
Joe, check the archives for 'spigot bushing' . Bud
|I thought I had searched in the archives for everything possible, but I hadnít looked for ďspigot bushingĒ, and, Bud, it looks like you had close to the same problem I have. When I test fitted the clutch alignment tool into the bushing it seemed to go in fairly easily. I did think to check the diameters of the plastic clutch tool and the 1st motion shaft with a micrometer and found the clutch tool seems to be a few thousandths of an inch smaller than the 1st motion shaft and is of course much less rigid, which might explain why it inserts fairly easily and the shaft doesnít.|
Unless something else pops up, it looks like my next move probably will be to remove the gearbox again and try to replace the pilot bushing. Another fun-filled week ahead! Iíll let you know how it goes. Thanks for all your responses and suggestions.
|Joe, Is your pressure plate the original style Borg and Beck or the newer diaphragm type?|
You mention the bellhousing did not want to separate and then didn't want to close up. Did you ever try sliding the clutch disc on the shaft splines? That may be where it is binding.
I don't know if it is physically possible, but did you perchance stick an 8" disc in with the 7 1/4" pressureplate? Probably not, but just had to raise the question. That still wouldn't explain the bellhousing struggles.
I realize your son pushed the car and the engine rolled, which indicated a pretty good bind, but that was before you removed/replaced the tranny? Difficult to imagine that a "snug" shaft & bushing would roll the engine with out breaking loose.
Try using the hand crank to evaluate how much resistance you have.
Pull the plugs and roll the engine over in nuetral just to get a feel for the engine resistance.
Then put it in fourth gear and have someone step on the brakes and push in the clutch. See how much extra resistance you encounter IF you can crank the engine around.
Just maybe it might be light enough now to where it'll break in IF it is just tight in the bushing.
|Thanks guys. The pressure plate is original style 8Ē unit. It was replaced in the early Ď70ís but has less than 2000 miles on it. The new clutch disc slides without binding on the shaft. I did think to try that before re-installing the gearbox. I think itís a long shot that things will have freed up much now, but itís easy enough to put the driveshaft back on and find out for sure. Itís certainly a lot easier than removing the gearbox again, so Iíll try it.|
|ďTry using the hand crank to evaluate how much resistance you have.Ē Good advice! Iím glad I followed it. |
There wasnít much extra resistance. I was able to start the car in gear and after driving back and forth in the driveway a few times I could shift into all four forward gears ok, but not into reverse while the engine was running. After talking to the machinist who did most of the work on my engine, I decided to take a chance that it will loosen up a bit and work properly if itís just a small irregularity. However, if the OD of the 1st motion shaft is actually too big for the pilot bearing ID, then maybe it wonít break in and Iíll have to take the gearbox out and fix it after all, but I plan to drive it a couple hundred miles or so before making that decision. Does anybody see any problem with that approach?
Incidentally, I was happily surprised how much difference the OíConnor modification made. The clutch operation was much easier and smoother than I remembered.
I am pleased that the starting handle method got you one step further. I will repeat my suggestion of going back to the original hole in the drop lever (remove the O conor mod.), this may solve your reverse gear issue.
" I could shift into all four forward gears ok, but not into reverse" Did it shift into the forward gears at a standstill or while driving? I assume it was shifting 1 thru 4 while driving and reverse was reluctant while sitting still.
If it isn't grinding with the forward gears at a standstill, then it ought to engage reverse, too.
Fine tune the clutch adjustment as best you can, since you can have too little or too much throw, aggravating the situation. Search for that real sweet spot.
The more time spent with the car in gear/clutch in/standing still, the more the bushing will break in. I don't even like sitting at a long stop light with the clutch in, thinking about a graphite throwout bearing heating up, so I don't advocate sitting there for any abnormally long length of time... in other words, normal driving may be just the ticket.
This might be a waste of time, but changing the trans oil to a very heavy gear lube may offer a tad more resistance in the tranny to help arrest the clutch disc when the pressure plate disengages at standstill, if reverse & first still grind a bit.
I was just recalling that frustation of gears grinding and failing to engage, as I replaced the clutch in our Fiero TWICE last fall, and it still wouldn't disengage. Horribly bad hydraulic clutch system. I gave up and had to "Jimmy" the master clutch cylinder rod to my own longer dimension! It never, EVER, shifted worth a damn since we owned it, until now!
We need an update... how's it driving.
|Thanks for your interest. Life always seems to get in the way of what I have planned, so I haven't had time lately to do much with the car except look wistfully at it every time I open the garage door. I'll give you an update when I have anything to report. Soon, I hope!|
|Some of us work very slowly, but Iím happy to report that my car is running well and is back on the road for the first time since 1983! The pilot bushing just needed a little running-in and now everything works perfectly. I am especially happy with the OíConnor modification of the clutch linkageóthe clutch is much smoother and easier to operate than I remember it used to be. Thanks for all the help from this forum. I need to put the hood/bonnet back on the car and then Iíll post a picture or two.|
|Congrats Joe! Cheers |
Peter TD 5801
This thread was discussed between 26/05/2014 and 31/07/2014
MG TD TF 1500 index
This thread is from the archive. The Live MG TD TF 1500 BBS is active now.