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 Clutch problems. Pedal travel too short?

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T O P I C    R E V I E W
andydeans3Posted - 17 Jan 2020 : 12:14:50
I've just fitted a refurbished gearbox in my car. Since the engine was out, I also fitted a relined clutch plate. (Standard clutch, not a diaphragm clutch.)
The older 4 spring clutch plate that does not have problems with things being riveted round the wrong way. They fitted 3.2mm thick lining, overall thickness from one side to other around 8.4mm, though there was one small section, where it was near 9 mm to 9.2mm.

Also fitted a new release bearing.

Having got it all together now, I only seem to have 50mm of clutch pedal travel, way, way short of the floor of the car. At the window, where you can see the clutch arm moving on the gearbox bell housing, the arm is moving about 12mm. The back edge is only "just" disappearing into the bell housing, Hitting something very solid, bottoming out I guess, but why?

I never touched the clutch hydraulics. Just unbolted the slave and tied it to the side.

Crunching like hell trying to get it into reverse, and hard to get it into first.I haven't got the front on the car yet, so have not been out on the road.Something is not clearly not right.

I'm pretty sure the engine will have to come out again, but I'll hold back on that till I get some advice.

Maybe I should bite the bullet, and convert to a diaphragm!

Andy

1978 LHD SAAB 96
1978 MGB Roadster
2008 LHD "Classic" Renault Twingo
1991 Nissan Figaro
15   L A T E S T    R E P L I E S    (Newest First)
greg124Posted - 28 Sep 2021 : 16:53:29
I found the problem. Thanks Andy. Pulling back the rubber boot revealed that the end of the piston was protruding from the cylinder. The circlip was missing. I imagine the remnants must be languishing in the bottom of the bell housing.
As there was a rebuild kit among the box of spares that came with the car, I thought it a good opportunity to replace the seal as well. With the addition of a washer behind the slave cylinder to act as a shim, it all seems to work perfectly now.

Having said that, the position of the assembly at rest is not the same as on my 95. The front end of the rod is significantly vertically lower, such that the rod does not travel along the same line as the piston. I will look into this further when I have the engine out to cure the 'constant loss lubrication system'.
andydeans3Posted - 21 Sep 2021 : 22:45:57
Mmm, if the clutch operating arm is coming into contact with the clutch/flywheel assembly after only a fraction of an inch of arm movement, then there must be something seriously wrong.

Before doing anything drastic, check the clearance, and if you can get access to another 96, pull back the rubber cover on the bell housing where the clutch actuator goes in, and compare the position of the assembly at rest, and compare how far it moves in.
You could also check back at the beginning of this thread, somewhere there I noted some measurements of the actuating system in motion.
If you weren't so far away, I'd come and have a look!


My clutch has worked perfectly since shimming the slave cylinder forward slightly last year, as outlined further back in this thread.
If I remove all of the carpets/sound deadening material, and really push the clutch hard to the bare floor, I can just get the operating arm to make contact with the Flywheel/Clutch assembly.
It sounds really 'orrible!!!



1978 LHD SAAB 96
1978 MGB Roadster
2008 LHD "Classic" Renault Twingo
1991 Nissan Figaro
greg124Posted - 15 Sep 2021 : 17:35:09
My car has just developed a fault which may be partly related to this.
The clutch biting point has always been quite high in the time I've had the car, and I've never been able to adjust out the grinding noise (as mentioned above)with the pedal fully depressed. This morning I reversed the car across the yard and when putting it in first gear we failed to proceed. I'm expecting the friction plate to need replacing.
However, I decided to bleed the hydraulics to see whether it made any difference, and now the pedal can only be depressed about 2 inches, but with the engine running only a fraction of an inch depression before the grinding starts.
I'm beginning to wonder if I might have a bent release arm?
Iain GPosted - 06 Feb 2020 : 14:47:13
New diaphragms from Malbrad are direct fit and don’t need modified flywheel.
Older or used ones might.

Iain G
Betsy67Posted - 06 Feb 2020 : 07:15:03
Iain G - sounds reasonable to me.
I have a spare pressure plate as well as the VW diaphragms, so I'll probably have a bit of a 'play' at sometime when it warms up a bit. Been rather busy with Betsy since December and hopefully all sorted now. Had a few shortish test drives and all appears ok.
Does the flywheel need drilling and tapping to accommodate the diaphragm ?
Iain GPosted - 05 Feb 2020 : 14:28:55
From my own painful experience I know that one way or another you need to have the centre plate on the clutch cover, which contacts the release bearing, protruding just above the main domed shape of the clutch cover pressing. Just a millimetre or two. If the centre plate is below the dome then it is too much travel for the release bearing and you end up shimming the slave cylinder forwards which is the common bodge and can lead to clutch sticking and/or release arm catching the clutch cover. You can achieve the right height by shimming under the clutch cover bolts or skimming the flywheel. Same for spring or diaphragm clutches with the donut. I know some diaphragms don’t have the donut and you must use a thicker stepped release bearing with these not the flat type. You set these with fingers pointing outwards slightly. Never inwards.
Hope I have explained ok.

Iain G
Betsy67Posted - 05 Feb 2020 : 07:13:17
Quite interested in the VW clutch fitting details.
Think I have two variants in my garage. One from an Air cooled T/P and another from a T4.
Not sure which one I've been messing about with, but it fits in the Saab flywheel nicely.
Is the correct option the 200 or 220mm Diaphragm ?
VLMPosted - 04 Feb 2020 : 04:30:11
GavinC: I'll get back to you in a day or so. JN, a fellow who works for/with me on the things (and everything else as well - he is a master of all things mechanical) will be back in tomorrow. We have a rather "snappy" lathe in the barn and he did the work with it. I will get the measurements from him. We may have an "ortho 3D" of the flywheel as currently turned down. If so, I will post it.

VLM
GavincPosted - 02 Feb 2020 : 21:25:53
Thats interesting VLM, how much did you take out of the flywheel? I took mine down to fit a VW clutch, but you then start to have clearance issues with the flywheel bolts. I had to take a skim off the bolts also, and still needed to use shim washers on the spring plate.

96V4 stage rally car
99 stage rally car.
VLMPosted - 02 Feb 2020 : 11:38:38
A better solution in the long term is to have the flywheel recut the next time that the engine is out (if there ever is a next time) to get the correct depth for clearance without resorting to shims. I just converted to a 200mm VW clutch/flywheel setup and made the depth adjustments on the lightened flywheel rather than go with shims.
andydeans3Posted - 19 Jan 2020 : 22:53:07
Melle.

Yeah, getting a bit long winded, main thing is that the car's working fine now!
I see that the Great Western Classic car Show is on at the Royal bath and West, 8th/9th February, so you never know.
Andy

1978 LHD SAAB 96
1978 MGB Roadster
2008 LHD "Classic" Renault Twingo
1991 Nissan Figaro
mellePosted - 19 Jan 2020 : 20:55:45
We'll have a look at it next time you're in Bath; tea and cake at the ready. :D

www.saabv4.com
andydeans3Posted - 19 Jan 2020 : 20:31:29
Melle
Aye, the slave cylinder is supposed to sit "all the way back", but due to the vagaries of the clutch pressure plate set up, it would seem that it's sometimes necessary to shim it forward slightly.
My mechanic friend was a SAAB mechanic from the late 60s, through to the early 2000s, and tells me it was standard practice at the time, among other bodges. (Like dropping slotted washers through the inspection window!). This was at a main SAAB dealer, not a back street bodge shop!

The spring on the clutch assembly is not broken.
When the system is at rest, and the slave piston is "relaxed", the position of the piston in the bore will be dependent on the relative position of the slave cylinder to the operating rod.
Shim the slave cylinder forward, and the piston will move back, and therefore give more "stroke" so to say.

Before I shimmed the slave cylinder forward by 2 or 3 mm, the pedal only moved about 50 mm, because the piston was coming up against the circlip at the end, ie it had run out of travel.
The clutch was not clearing, could not get the car into reverse without a lot of crunching.
Shimmed the cylinder forward 2 or 3 mm, ( I didn't measure it, but it's about 2 or 3 mm) and hey presto, pedal goes to the floor, and all gears are smooth. I may have shimmed it too far, because the rod was just fouling the clutch cover. Re-setting the free play fixed that.
I'm going to experiment again tomorrow because when everything has expanded at full temperature the fouling might come back

It's quite hard to explain this all in words. Maybe some cartoons would help

1978 LHD SAAB 96
1978 MGB Roadster
2008 LHD "Classic" Renault Twingo
1991 Nissan Figaro
mellePosted - 19 Jan 2020 : 19:19:35
quote:
Originally posted by andydeans3
There's nothing wrong with the hydraulics, the slave cylinder is simply sitting too far back.
But it's designed to sit all the way back?

quote:
Originally posted by andydeans3
This means that once the rod is in place , the piston is already part way along the bore. Push the pedal, and the piston moves along the bore, and comes up against the circlip, before the clutch is fully extended,(because the piston didn't start from the back end of cylinder)
If the piston in the slave doesn't fully retract the spring is probably broken?

quote:
Originally posted by deggsie
may be a copy on Melle's website ?
No, this is copyrighted material so I can't publish it on my website.

www.saabv4.com
deggsiePosted - 19 Jan 2020 : 16:16:36
I've been following this thread with great interest ... since my engine rebuild and re-installation, I have had arguably the opposite problem, the clutch only operates with the pedal right down by the floor.
Initially it wouldn't release at all, so shimmed the slave forward a bit (2mm) and it worked fine on all forward (synchromeshed) gears, but graunched into reverse. Had the symptom of the release arm fouling the clutch cover when the engine was warm and the clutch pedal was pressed hard.
Shimmed the slave a bit more (another 2mm = 4mm in total) and adjusted the free play, now works reasonably OK but can still be noisy into reverse when hot.
The guy who rebuilt the engine for me mentioned there were "washers on the heads of the pressure plate bolts" that he didn't think should be there and so omitted on rebuild, but I suspect that they were actually spacers between the pressure plate and the flywheel (we didn't replace any of the clutch parts as it worked fine before the engine problems - probably false economy).
It's too cold in the garage for any lengthy work at the mo, but may try to reinsert some spacers when the weather improves.
Jack Ashcraft's "Transmission Survival Guide" (p. 47 - may be a copy on Melle's website ?) shows a diagram of 'trouser' shims with a hole in the bent tab to aid installation/removal), anyone familiar with these ?

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