Clutch judder

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LaughingBoy
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Clutch judder

Post by LaughingBoy »

I have had ongoing problems with clutch judder. This is my current configuration:

Ital 1275 A+ Series modified engine
Modified Minor 1098 flywheel
1098 Sprite/Midget clutch cover (springs)
1275 Sprite/Midget carbon thrust bearing
Toyota 7.5" clutch friction plate
Toyota T50 5-speed gearbox (21 spline input shaft)

The engine produces about 86bhp max at flywheel (although that could be more now as it has been further tuned since bhp was last measured).

I have replaced the clutch on several occasions but the judder always re-appears and gets worse over time. At the moment it is intermittent and only occurs when the clutch gets hot in stop-start traffic. A really nasty shuddering vibration.

I have a good rear crank oil seal fitted and on no occasion have I found the clutch to be contaminated.

I am almost certainly going to upgrade the flywheel and clutch assembly with a lightened flywheel and heavy-duty diaphragm clutch + roller release bearing. This is more appropriate for the engine I think. But I'm not 100% convinced that the current clutch config is the sole cause of the judder.

Looking under the car I noticed that the driveline angle is not completely straight - i.e. the end of the gearbox points downwards a bit as does the differential nose. So the propshaft UJ's are always at an angle if you see what I mean. This seems to be normal for the Toyota 5-speed conversion but doesn't seem ideal to me. Can anyone else who has the 5-speed Toyota box confirm? I'm wondering if the fact that the transmission is not 'straight' could be contributing to or causing the judder problem.

Hopefully even if that is the case the upgraded clutch will compensate and solve the problem but I'm very interested to hear peoples' thoughts ...
oliver90owner
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Re: Clutch judder

Post by oliver90owner »

If the judder is when taking up the drive from a standstill situation, I don’t think the U/J angle being slightly off should affect the clutch operation - the clutch is between the engine and gearbox, after all and the U/J is stationary.

Any non-linear drive-train is not good. It should be straight when operating ‘normally’. Maybe your rear axle alignment is a problem? Checking the gearbox and engine mounts might be a sensible move, as well as engine and gearbox restraints.

I might suspect the alignment of any modified mounting plates between the engine and gearbox.

Good luck and get looking for the problem. It clearly has a cause - and will not go away until corrected.
kevin s
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Re: Clutch judder

Post by kevin s »

Loads of RWD cars and vans have a few degrees of angle on the prop joints without any problems, I'd be surprised if that was the cause especially as it only happens after sitting in traffic, how are you actuating the clutch? the mechanical linkage can cause judder as the engine moves on it's mounts.
don58van
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Re: Clutch judder

Post by don58van »

the driveline angle is not completely straight - i.e. the end of the gearbox points downwards a bit as does the differential nose. So the propshaft UJ's are always at an angle
The UJs have to be at an angle. They will not work correctly if they are perfectly in line. In fact in-line UJs are a potential cause of vibration.

Don
LaughingBoy
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Re: Clutch judder

Post by LaughingBoy »

Many thanks for your replies.

I have standard mechanical clutch linkage. May have to swap to hydraulic clutch when I upgrade. Or use another hole which I drilled in the drop arm many moons ago when I had the 6.5" Sprite diaphragm clutch.

So, it doesn't sound like it's the driveline angle (it was a long shot but I had read somewhere yesterday that if it's more than 3 degrees at either g'box or diff it can cause judder/vibration - hence my query).

Yes the judder occurs moving off from stationary and once the car is moving all is well - so it's just on clutch take-up.

The last time it occurred I replaced the engine mountings, replaced and adjusted the engine steady bar, and checked the gearbox mounting. I also had the flwheel re-faced. Then 500 miles later the problem recurred although it was the first time I had been stuck in a bad traffic jam (stop/start every 5 seconds) so I guess the probem might not have been solved in the first place.

Graham
kevin s
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Re: Clutch judder

Post by kevin s »

The mounts will soften with the heat when you sit in traffic and given one of the factors which affects judder is driveline stiffness would mean it becomes evident, a hydraulic clutch would certainly help, the problem with mechanical linkages is the clutch engagement is effected by engine movement so you can get into a circular effect where the clutch begins to engage, the engine moves, this reduces the amount of engagement because of the mechanical linkage, the mounts then relax with the reduction in load and the engagement goes up again so on such that you get Judder. the steady bar and cable are there to limit engine movement but at the expense of refinement.

We have a hydraulic clutch and it works perfectly with no cable or engine steady.
LaughingBoy
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Re: Clutch judder

Post by LaughingBoy »

When I replaced the mounts I used supposedly high quality softer mounts from CW MMC - I think the idea was that the softer mounts absorb more vibration.
the clutch begins to engage, the engine moves, this reduces the amount of engagement because of the mechanical linkage, the mounts then relax with the reduction in load and the engagement goes up again so on such that you get Judder.
I don't fully understand - yes, the clutch engagement can make the engine move but how does this reduce the amount of engagement because of the mechanical linkage?
Chipper
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Re: Clutch judder

Post by Chipper »

I think he means that as you push the clutch in, it slightly nudges the engine/gearbox forwards on its mounts (particularly if you've fitted softer ones), thus reducing the effort exerted on the clutch release bearing, hence the clutch doesn't disengage as much as would normally be expected...
Maurice, E. Kent
(1970 Traveller)
philthehill
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Re: Clutch judder

Post by philthehill »

The loading on the clutch release mechanism is determined by the pressure plate springs/diaphragm and nothing else though the clutch release pedal spring will have a small loading on the release mechanism but not on the release bearing.
I suspect that the fitment of the Toyota gearbox to the BMC engine is not fully in alignment and/or the flywheel is not concentric to the crankshaft. Did you do the flywheel yourself or use a ESM modified flywheel? The centre of the ESM flywheel has a bush which fits into the rear counterbore of the crankshaft so ensuring that the flywheel is concentric to the crankshaft.
Have you checked the run out of the flywheel both for concentricity (circumferance/edge run out) and lateral (rear face) run out?

LaughingBoy
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Re: Clutch judder

Post by LaughingBoy »

The 1098 modified flywheel was supplied by Charles Ware Morris Minor Centre back in 1998 I think - so it certainly should be concentric with no run-out.
I don't see how the gearbox could be misaligned unless the bellhousing is mis-shapen.
philthehill
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Re: Clutch judder

Post by philthehill »

Unless you measure you cannot be sure that everything is as it should be.
Way back things like adapter bell housings and flywheels were not made to the same tolerances as they are now.
I have a CS Autoclassics adapter bell housing fitted to my Minor to allow me to fit what was originally a Ford 2000E gearbox and I had to carry out additional work to make sure that everything was as it should be and it to be able to cope with additional power.
In the extreme - some adapter bell housings were just shortened bell housing from a BMC 'A' series gearbox with adapter plates welded onto the rear of the bell housing.
A photo or photos of what you have would be appreciated.

kevin s
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Re: Clutch judder

Post by kevin s »

LaughingBoy wrote: Thu Mar 10, 2022 5:18 pm When I replaced the mounts I used supposedly high quality softer mounts from CW MMC - I think the idea was that the softer mounts absorb more vibration.
the clutch begins to engage, the engine moves, this reduces the amount of engagement because of the mechanical linkage, the mounts then relax with the reduction in load and the engagement goes up again so on such that you get Judder.
I don't fully understand - yes, the clutch engagement can make the engine move but how does this reduce the amount of engagement because of the mechanical linkage?
The clutch pedal is fixed to the body, when the engine moves in it's mounts as the body end of the linkage stays stationary the gearbox end will move will slightly affecting the clutch actuation (it only takes a tiny amount around the engagement point). The gearbox restraint cable is to limit the engine moving as it reacts the longitudinal force from the linkage and the steady bar resists the rotational displacement in the mounts. By fitting a more powerful engine and I assume heavier clutch you may have reached the limits of the standard mechanical clutch actuation.

If it were an alignment issue I don't think it would only do it when hot, and it would also destroy clutch hubs regularly.
jaekl
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Re: Clutch judder

Post by jaekl »

Clutch engagement with the mechanical linkage does not move the engine forward. If there is any movement it would be rearward because the external force is rearward. However, the relay shaft that pivots in the gearbox limits the effect of the external force from the clutch pedal. Internally there is a forward force on the crankshaft. The rocking of the engine can affect the relative movement of the clutch linkage minimally, so the steady on the cylinder head was added. The cable on the gearbox is strictly for deceleration to hold the engine in place.
LaughingBoy
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Re: Clutch judder

Post by LaughingBoy »

All comments much appreciated.

Kevin - I understand now ...

I don't think there is a gearbox restraint cable on the Toyota 5-speed box conversion - it sits on a rubber mount mounted to a cross-member. This could be part of the problem. The engine steady bar will not prevent longitudinal movement so I may have an issue there.

Anyway I have bought a new lightened flywheel (which should be concentric!), a heavy-duty 7.5" diaphragm clutch + roller release bearing. I will also seek out a hydraulic clutch conversion kit. Hopefully all should be OK then ...
LaughingBoy
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Re: Clutch judder

Post by LaughingBoy »

A photo or photos of what you have would be appreciated.
Phil ... here are a couple of photos of my bellhousing & g'box. It may not be enough for you to see properly but it's all I have for the moment until I'm next under the car.
Bellhousing_1_opt.jpg
Bellhousing_1_opt.jpg (90.01 KiB) Viewed 1190 times
IMG_20200605_171516_cropped.jpg
IMG_20200605_171516_cropped.jpg (524.31 KiB) Viewed 1190 times
philthehill
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Re: Clutch judder

Post by philthehill »

Many thanks for the photos.
Does the clutch release bearing move on a carrier tube attached to the front of the gearbox in a similar manner to the Ford gearbox?
If the clutch release bearing moves on a carrier tube and the clutch release lever pivot point is fixed the two cannot move in a proper manner as they are both moving in different arcs or planes. This could lead to clutch judder as the bearing will move in a orbital motion on the pressure plate release pad.
I had a similar problem but overcame the issue with the fitment of a roller release bearing on a carrier that allowed the carrier and arm to move in different arcs/planes.
Some adapter kits have a slotted hole for the release lever pivot so allowing the release arm to follow the same plane as the release bearing.

LaughingBoy
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Re: Clutch judder

Post by LaughingBoy »

No I don't think there is a carrier tube. As far as I recall the Sprite 1275 carbon thrust bearing mounts directly on the fork ...
LaughingBoy
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Re: Clutch judder

Post by LaughingBoy »

.... just had a quick look at the mechanical linkage and it all seems completely non-standard. I have not paid much attention to it in the past but it must have been altered by CW MMC when they put the Toyota 5-speed box in. I will try and take some better photos but the relay shaft is only attached to the chassis not the gearbox. The rod has been replaced with a cable and the straight arm on the shaft doesn't seem to be used - i.e. the relay plate is not mounted in the hole at the end ...
clutch_linkage.jpg
clutch_linkage.jpg (45.62 KiB) Viewed 1087 times
LaughingBoy
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Re: Clutch judder

Post by LaughingBoy »

Not sure this has anything to do with my clutch judder but my mechanical linkage is very different. The linkage cross/relay shaft has been completely removed. The clutch pedal cross shaft has been extended with a drop leg welded on which is directly connected via a cable to the clutch release fork. The existing pedal shaft drop leg (near the chassis longitudinal member) is still there but is obviously not connected via relay plates to the missing cross/relay shaft. All very unusual - here are some more pics. I don't know if this arrangement makes the clutch softer or heavier or makes no difference?
Clutch_linkage_1.jpg
Clutch_linkage_1.jpg (85.44 KiB) Viewed 1033 times
Clutch_linkage_2.jpg
Clutch_linkage_2.jpg (91.47 KiB) Viewed 1033 times
kevin s
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Re: Clutch judder

Post by kevin s »

It's far from ideal , I'd see if you either fit a hydraulic actuation or a cable system with a inner / outer and a bit of curvature.
Stiffer mounts would help but it would mean more noise / vibration.
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