Joined: May 2020 Posts: 20 Threads: 5
Reputation:
0
I am having problems with the clutch dragging on my car. 1930 3 speed box. Fine engaging 1st gear when cold, but it is impossible to engage without mashing the gears, when the gearbox has warmed up. Idle is not excessively fast and using an EP 80/90 gear oil. I note in previous threads that various people have suggested that the incorrect length splined spigot on the driven plate may be the culprit, resulting in it bottoming out in the gearbox input/constant mesh gear shaft. I wondered what the different lengths of spigot are, so I can check mine and perhaps take a fraction off the end with a grinder, or find another one. Surely though, the difference in lengths can't be that borderline.... Alternatively, I wondered whether a worn driven plate spigot could be allowing the driven plate to flop down slightly and rub against the pressure plate at the bottom. I think it would have to be completely knackered to do so, which mine is not. I also note that the clutch pedal sometimes slowly comes up, when you take your foot off it, and I wondered whether this could indicate a worn thrust bearing register on the gearbox.
Any thoughts?
Nick
Joined: Aug 2017 Posts: 923 Threads: 6
Reputation:
10
Location: Scottish Borders
I can confirme that the longer spined spigot is a problem. When I fitted the wrong one in our car it was impossible to engage the gear at all.
The gearbos shoule be lubricated with engine oil, in our case SAE 30.
Jim
Joined: Aug 2017 Posts: 809 Threads: 72
Reputation:
9
I had a similar problem after fitting a clutch centre plate from another car. It was the correct length but the splines had worn with a very slight step, enough to discourage it from disengaging freely.
Joined: Mar 2015 Posts: 5,195 Threads: 223
Reputation:
59
Location: Scotchland
06-06-2023, 10:04 PM
(This post was last modified: 06-06-2023, 10:04 PM by Ruairidh Dunford.)
Hi Nick,
There at least 4 lengths of splines, a 1mm cutting disc will safely remove 1/8" and reduce it suitably, if you have the longest.
Some modern clutch linings are thicker than original, these can prevent the clutch opening fully, spacing out the cover plate with suitable washers will overcome the issue.
Some flywheel nut lock washers are too wide and hold up the centre plate, inside the dome, they can be trimmed using a sharp chisel.
A7 gearboxes should use SAE30 or 20/50, anything thicker is not really suitable, in my experience.
Hope this helps find a solution.
Ruairidh
Joined: Aug 2017 Posts: 1,454 Threads: 21
Reputation:
15
Location: The village of Evenley
Car type: 1934 Austin Seven RP Deluxe
Brilliant response Ruairidh, a couple of things I hadn’t considered, that’s for sure!
Joined: May 2020 Posts: 20 Threads: 5
Reputation:
0
Thanks Ruairidh,
I've tried shimming the bell housing out from the crankcase. Doesn't seem to have made any difference, which rules out the spigot being too long and bottoming out. I can spin the input shaft around with the lid off the box and clutch depressed, and the driven plate seems to turn freely. I wonder whether the crank/flywheel nut/washer is fouling the boss. It must be something that has enough friction to spin the input shaft when the oil is hot. Could be that the driven plate is not fully disengaging and still rubbing on either the front or rear linings. I've always used gear oil, and I would think that engine oil will only make the situation worse..
best,
Nick
Joined: Mar 2015 Posts: 5,195 Threads: 223
Reputation:
59
Location: Scotchland
Hi Nick,
I have only ever used engine oil in gearboxes but Terry Griffin uses GL4 75/90, which is as good recommendation as you will ever get, in my book.
Ruairidh
Joined: May 2020 Posts: 20 Threads: 5
Reputation:
0
Charles,
I shimmed out using some circa 16-14 swg ali sheet. I think if it was just binding that would be sufficient.. I've decided to bite the bullet and take the engine and box out to investigate it further. At least I can see what's going on on the bench, rather than grovelling under the scuttle!
Nick
Joined: Mar 2015 Posts: 5,195 Threads: 223
Reputation:
59
Location: Scotchland
If your linings are too thick, the spacers need to go between the cover plate and the flywheel, not the bellhousing, Nick.
