Joined: Apr 2018 Posts: 191 Threads: 76
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Hi,
I've just fitted a new clutch pressure plate to my 3-speed engine / gearbox and fitted a new lining to this but not to the flywheel as it's only done 1,000 miles or so and I didn't want to remove the flywheel.
The clutch assembly seems to fit fine and before fitting the gear box the clutch driven plate seemed to be tightly gripped by clutch pressure plate / flywheel.
After fitting the gearbox however, and with the box in 1st gear, i can just about turn the gearbox output shaft without turning the engine so obviously the clutch is slipping.
I've noticed that there is now no free play in the clutch pedal and also the thrust bearing housing can't be rattled about which I'm fairly sure it could be before.
I'm wondering if it could be as simple as the toggle arms not being correctly engaged in the slots in the thrust race but I've tried taking it out and re-fitting and there's not much difference.
Any suggestions? Also is there a recommended method for ensuring the clutch arms are correctly in the thrust race?
I fitted the thrust race to the clutch first and then offered up the gearbox since it meant I could check the toggles were OK but obviously they could have moved whilst I was trying to slide the gearbox into position and lining up the double spline. Would it be better to have the thrust race in the gearbox first?
John.
Joined: Mar 2015 Posts: 5,436 Threads: 231
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Location: Scotchland
The whole clutch thrust assembly may have rotated slightly and is now catching - can you see the oiler hole at top dead centre or is it off to one side slightly?
Joined: Apr 2018 Posts: 191 Threads: 76
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Oiler hole appears to be OK and I'm now more confident the toggles are located correctly in the thrust race.
However the part of the toggle which engages against the thrust race is much less than the 5/16" I have seen mentioned in various articles before, in fact it's no more than 1/16" at most.
This is curious because the only part I've changed is the clutch back plate which carries the ring gear and everything else is as it was when it worked OK.
The "new" back plate had previously been repaired by the process of fitting grub screws into the bottom of the toggle lever slots to allow for more clutch disengagement. I am wondering if this was overdone to compensate for wear in other areas of the clutch mechanism and because of the ratio between the pivot to grub screw dimension and the pivot to toggle end dimension then a relatively small difference in height here would affect the 5/16" dimension more significantly.
I'll need to try to confirm this before doing anything but I'm not at all sure how I would go about reducing them now the new lining is riveted on and the toggles can't be removed. I have only very limited equipment but may be able to put it under my pillar drill and try to spot face it using a slot drill. What do you think?
John.
Joined: Mar 2015 Posts: 5,436 Threads: 231
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Location: Scotchland
If the slots have been ‘repaired’ and you suspect this is causing the problem - release the gearbox from the bellhousing a little and see if things improve.
If they do - you could make up spacers to put over the studs.
Joined: Apr 2018 Posts: 191 Threads: 76
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Thanks for all the help so far, and apologies if the following is rather long winded.
This morning I had another look at the issue and made some more accurate measurements which makes me think I now know what's wrong but not exactly the best way to resolve it.
Initially I measured the dimension from the bottom if the slots in the thrust race to the face of the gearbox which mates with the engine. As far as I can establish this makes the bottom of the slots (where the toggles bear) 0.182" proud of the gearbox face.
When I had the clutch assembly bolted in position on the flywheel the ends of the toggles were virtually flush with the face of the the casting which mates with the gearbox. As a result the toggles would be compressed by around 0.182" when the gearbox is bolted on which would explain why the clutch is at the point of slipping.
To rectify this and allow for a little free play in the mechanism I was thinking I would adjust the depth of the toggle slots to give me something like 1/16" of clearance. This would mean altering the slot depth so that the ends of the toggles would be around 1/4" below the gearbox mounting face.
There is something like a 3:1 ratio built into the toggle mechanism so to achieve 1/4" of clearance I would need to deepen the toggle slots by around 0.083".
I then measured the depth of the toggle slots in my "new" back plate and although these vary slightly due to wear the average depth is 0.230" so if I were to deepen them by 0.083" they would become 0.333" deep although I suspect the slots were originally 5/16" (0.312") deep because on another Ruby type plate the unworn area seems to be 5/16" deep.
This all seemed fine and I was thinking I'd simply file down the repair pegs in the bottom of the toggle slots by something between 0.062" and 0.083" depending upon whether I based it on the slot depth being 5/16" or the calculated 0.333". This would move the toggle ends by around 1/4" and remove the clutch slip whilst hopefully still giving me good disengagement.
Now the problem. I don't really know how the repair pins were fixed into the bottom of the toggle slots but it looks as though they are actually headed pins pushed in from the slot side and then peened over on the back. The thickness of the head above the bottom of the slot is probably around 0.100 so if I remove 0.062 then there may be only 0.038 of material left and even less if I were to remove 0.083".
Trouble is I just don't know if this will be OK. The alternative is obviously to do as others have suggested and add spacers between the gearbox and engine but these would need to be around 1/4" long which would mean the gearbox flange no longer engaged in the engine casting.
What do you think?
