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Big Transmission failure; Gear selection screwed
Topic Started: Sep 29 2011, 10:20 AM (2,340 Views)
Paul
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Hello All,

After a couple of years pottering where the car's made good progress, had a heck of a lot of bits replaced and was looking as if it could go for its MOT soon last Sunday about 2 weeks ago proved to be the closest I've come to torching it.

Last month I moved it and the gear selection wouldn't work but I put it down to the gear lever having been removed and replaced recently. However attempts to fix things at this end proved futile. The scratchy clutch symptom seems to point to something more major as well.

Essentially I think the clutch set-up is broken/flawed/rubbish/screwed: more info below. Ideas welcome!

Background:

  • Engine's run OK for a while now (albeit with a bit of a knocking noise)
  • Gear selection works fine and gear ratios could be seen working when pushing the car in gear.
  • The car is fitted with an adapter plate, a longer gearbox shaft and an extender bush on the VW gearbox side and it then uses a standard (brand new) Alfa clutch on a 8v 1700 AlfaSud/33 engine. Engine and adapter plate were purchased second-hand together quite a few years back. Gearbox was from a VW breaker. This was all fitted together on this car for the first time so I can't vouch for any of it working together.
  • I BELIEVE we had moved it before under its own power and had gears, but it's never been driven further than back and forward in the garage if it did.
  • There was a bang when we were working on the car a while back. It would have been sitting in neutral at this point as we were dealing with engine side of things, but I guess this could have been the clutch letting go, didn't twig at the time as we didn't try to move it immediately.

Symptoms:

  • Engine OFF: Gear selection works fine with engine off. Clutch pedal feels fine (not "scratchy") although I accept it's not necessary at this point anyway.
  • Engine Started in Neutral: The clutch pedal feels "scratchy" when depressed (but still moves and doesn't require a big increase in pressure) but the gear stick cannot be moved into gear.
  • Engine Started in Gear: The clutch pedal can be released and depressed and provides or stops drive to the wheels in the selected gear. Car can be moved both backwards and forwards by starting in the relevant gear. I cannot however get the car out of any initially selected gear, either into neutral or into another gear.

Most mentions of clutch problems I've read relate to fluid based systems having lost pressure and not moving far enough. This one is still cable based and the fact that I can engage and disengage the clutch if I've started the car in gear seems to imply it is moving as far as it needs.

I'm reluctant to stick a new clutch in without understanding better what's gone wrong - new Alfa clutches are an expensive diagnostic tool!

I guess ultimately it's going to have to be pulled apart to get a definitive idea of what's gone wrong, but does any one have any initial useful ideas/suggestions?

Any way of identifying whether it's Gearbox, Clutch, Adaptor Kit or Engine related?

If it ends up looking like being beyond my basic mechanical abilities i.e. if anything needs reworking/making can anyone recommend anywhere that'll deal with something like this?

Anyone fancy free beer/pizza and knows what they're looking for rather than my technical level which extends to the ability to nail/glue stuff together!

It will survive I guess, I know DS Tuning still make a different style of Adaptor if I need to replace that and I've another Alfa engine stored.
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iwantasandrail
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Hi Paul,

The problem could be with the "extender bush".
If your adaptor kit is like mine this bush is designed to be a sliding fit on the gearbox input shaft. If this bush has either picked-up on the input shaft or is not sliding freely it will effectively transfer engine rotation into the gearbox even if the clutch pedal is depressed. This will then make it impossible to engage a gear.
As this is driven only by friction between the bush and the shaft, starting the car in gear would effectivly overcome the friction and give the appearance that everything was working ok.
Question, was any grease applied to the bore of the bush when it was assembled onto the input shaft?

Paul
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iwantasandrail
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Paul,

One further thought, you mentioned a "bang".
This could have been one of the clutch release forks failing, if this were the case the clutch would still operate, after a fashion, but would mean that the release bearing would only push the extender bush on one side, this would then cause the bush to bind on the gearbox input shaft resulting in the gearbox being driven even when the clutch pedal is depressed and again meaning you couldn't engage any gears.

Paul


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steve_vfr
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Sounds like the clutch is dragging - if you can't get it in or out of gear with the engine running.
Clutch not being fully released for any reason or as the others say, anything rubbing or stuck in where it shouldn't be would cause it.
Is there an inspection point anywhere on the bell housing that you could shine a torch in and look at the clutch?

Steve
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Knighty
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HI paul - this sounds exactly like what happened to me, the clutch was dragging badly as the bobbin that slides over the gearbox shaft was about 2-3mm too long, so I took out the engine (bummer I know), and put the bobbin in a lathe and machined it down to a 1-2mm clearance size........its unfortunatley down to a piece of crap design from GB engineering.

to double check this, take your engine out and get a good quality steel ruler, then :

1) measure the protrusion of the clutch bearing face from the mating face of the engine

2) measure the depth of the clutch realeas bearing versus the gearbox mating face

then do the match and you should have 1-2mm clearance.......if you have an interference, then thats your problem, just take the bobbin down to a machine shop and get them to machine it down on a mill or a lathe, if you get stuck just send it to me and I'll get it done at work FOC, but you need to take the measurements first and be sure that is your problem.

yes agreed - you need grease on the bush bore too!!!

If you think your clutch is shagged, I have a spare 1.7 Alfa 33 item from when I replaced mine, I seem to remember from the friction plate measurements that I took that its only about 25% worn and versus what the manual said, its yours for 30......bell me if you want to talk, as I dont look at the forum much during the week.
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Paul
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Firstly thanks everyone, this is great stuff.

Just back from a nice weekend in the Malvern hills well away from the car so this is all off the top of my head.

Grease : Hmmmm, no I don't think we used any :-( I think we had the view that it was a copper bush and didn't need grease. Sounds like we may have made the wrong call there! What are we talking about here - A bit of Moly on the shaft? Presumably not enough to start throwing it around?

Inspection: Not sure there's any way of checking without pulling it apart. There's a small plug at the top for the timing but can't remember much else - will have a look in case I can pull the starter or something but think it's going to be engine out.

Extender piece: Cheers for the very useful post Knighty and the bits offer. Probably going to be a couple weeks till I can get the helper I need for pulling the engine and box out but will come in very handy.

Will keep this thread updated!

Cheers

Paul
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Wozzafug
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Hi.
If you haven't greased the splined shaft the friction plate could be seized or semi seized to it! This will cause drag and give your symptoms. The bang could be the plate releasing a bit if the pedal has been played with. If this is the case the engine and box will not seperate!
Incorrectly adjusted clutch could cause this ( made difficult by corrosion )
Warped flywheel or pressure plate! Does it judder when it takes up drive?
Or as mentioned the thrust bearing not being able to do it's job because of a badly made kit ( no experience on that one )
I've been a mechanic for twenty years and the fugitive I've recently bought is suffering from the first one. The gearbox and engine is sat on the floor with wedges shoved in around the joint waiting for the rust to let go and not break anything ( hopefully ) all for a bit of copper slip :angry:
Good luck. W
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Knighty
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Hi Paul - I also forgot to mention in my post above, this problem only seems to affect the later style of clutch release bearing.......hence I couldnt understand why it was never a problem before my gearbox was rebuilt when running the smaller 1.5 alfa boxer motor.........then I rememberd Peter from cog-box updated the release bearing to the later style as it was a more common part and supposedly a bit stronger......hence it appears the GB Engineering alfa-vw adaptor kit was designed for early swing-axle gearboxes.
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