Possible clutch disengagement problem

arebee

Hi all, since swapping out the M41 in my 122S Rally car project for a M410, I can't seem to be able to get the clutch to disengage properly. I have checked and adjusted the clutch pedal to ensure that I get fully travel of the clutch master cylinder (1 inch travel), this was with a Willwood 13/16 inch unit. I then found that the clutch fork also moved 1 inch when clutch pedal was fully pressed down. Thinking that some additional travel of the slave cylinder may help, I found a 3/4 inch ID clutch slave cylinder to replace the 13/16 inch one that was in the car, still no joy. Then swapped out the 13/16 inch master cylinder with a 7/8 inch one, bled system and tried again, still no joy. Gears want to crunch in 1st, 2nd, and reverse as well, indicating input shaft still rotating at full clutch pedal down. The slave cylinder piston movement is now around 35 mm, compared to initial 25 mm.

I am thinking that either I have a dud clutch setup (higher pressure standard clutch from Nordicar) or I have been a fool and for the first time in my life I have put the clutch disc in backwards!

Any other ideas welcome, since hopefully I can resolve this annoying problem during next weekend.

For the record, the M410 looked quite good inside prior to installation, synchros appeared largely unworn with no crunchy bits on any of the gear sets etc. The transmission seems to go into gears OK when engine is not running..

1971_144GL

Hi, the clutch bearing for the 164 and 144 style gearboxs are quite differnt, with the 164 style being thicker by quite a bit, and with quite a different arm that connects to the clutch hydraulics. I have a few sets here if you need a picture, including on a 164 m410.

Anyway, I am not sure which bearing the 410 version of the box uses in a B20 setup from factory as I have never dismantled that verison, even though a few australian p1800's have it - the smaller m40 style? Which version did you install? Is it possible that even with a working clutch fork/hydraulics you are still not geting enough pressure or correct contact angle, that might oterwise be corrected by the thicker bearing? Just a thought.

Interesting project, and glad to hear that others have not given up on the old style gearbox setup.

arebee

Hi 114GL,

I also have a 164 type M410, and can confirm your observation. The setup used for the B20 type M410 is the same as the M40/M41.

The other possibility is that one of the flywheel bolts has backed itself out enough to contact the clutch disc, but seems unlikely as I use lock tight on them.. The mystery will hopefully be revealed in the not too distant future…

arebee

Well the mystery has been solved, not something that I thought of previously I have to admit.

I removed the M410 from the Amazon, and found to my dismay that I had put the clutch friction disc in the correct way, the pilot bearing was also smooth and functioning well. This meant that further investigations were required. The hydraulic clutch fork setup in the 1800/M410 bellhousing was also cleared of any wrongdoing.

So I set up a flywheel in a vice, and bolted the clutch assembly to it. Using a bolt and a series of washers, I tightened the bolt to compress the spring diaphragm until the clutch disengaged. Only problem was that one side of the pressure plate was properly disengaged, whilst the other side was still slightly engaged, causing the transfer of unwanted rotational energy to the gearbox. The pressure plate was therefore not co-planar (is that the correct term?) to the flywheel face when supposedly disengaged, bugger. (For anyone wondering, I made sure to compress the fingers equally).

Also, trying for more clutch fork movement (using different diameter master cylinders / slave cylinders) eventually gets you properly stuck as well, since a kind of re-engagement occurs if one over compresses the pressure plate.

Luckily I have several other pressure plates at hand in my workshop (who doesn't….), and on testing those, no problems were identified. so I will reinstall the clutch / transmission next weekend.

dmc

So it was a failed pressure plate? That is a new one, one to remember.

I recall being taught to ease the bolts off a pressure plate evenly to ensure one side of the pressure plate or the fingers did not warp against the other side. Also to tighten them evenly for the same reason. I have never seen a failed one though, I have also been off the tools for 20 years.

Great to hear of a positive result.

Some progress on the template for the clutch slave mountings, more to come once finished…

arebee

So I got into touch with Frank De Vries at Nordicar, and explained my situation with the pressure plate, showed him the following pictures of the clutch on my bench with the setup I used to measure disengagement / partial engagement of the clutch. I used a feeler gauge to demonstrate the problem.

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A standard clutch for comparison…

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On seeing this weird problem, Frank agreed to immediately send a new 'reinforced' pressure plate of the type that I bought, and he and his team will check it first prior to sending it, how's that for service, even sending some additionally purchased items with the pressure plate at no freight charge to me.

Needless to say, very happy to do business with such reputable people at Nordicar.

arebee

Last week the replacement pressure plate arrived, and after double checking the disengagement (which Frank De Vries from Nordicar also had his staff do), confirmed that it was working perfectly, I installed the clutch, transmission etc, which all sounds easy, but since I also repair the families cars (XC90 , various V70's and S60.s etc…) I was delayed getting the final nuts and bolts done up.

I am now delighted to report that the new clutch works perfectly, and the M410 transmission now shifts well (and is actually quite smooth, what a relief!) Was hoping to go auto-crossing next weekend, but looks like the family tow car may have been pre-booked on another assignment, will see if I can somehow get a hold of it…