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Gearbox /clutch issues

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johnnyj
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Gearbox /clutch issues

Postby johnnyj » 04 Jan 2021 22:17

Hi folks

I mentioned in a previous post that I have problems with the gearbox/clutch. At the time I was working on the water pump and cooling, so put the gearbox issue out of my mind. Sadly however I now have to turn my attention to it and would appreciate your advice. Here goes:

- '77 2l FHC, 4 speed
- engine rebuilt (new crank, bearings, thrust washers etc)
- zero miles since rebuild
- engine runs fine
- new 3 piece clutch kit fitted from reputable '7 supplier

The problem: When the clutch is depressed with the engine running, something makes a hideous metal-on-metal screeching sound. It gets worse, and louder, the more the pedal is pressed. The engine revs drop the more the pedal is pressed, to the point that it would stall if pressed all the way. Naturally since the first time I discovered this, I haven't been doing a lot of it!

In my novice-like opinion I suspect one of these possibilities:

- excessive crank end-float
- faulty clutch release bearing (or slipper pads somehow dislodged?)

One other thing worth mentioning is that I changed the gearbox mount for the Volvo Febi type, and had been a bit concerned about getting the height correct using shims. It always bothered me that this was a bit hit & miss. Could the mounting being incorrectly shimmed cause this problem (not sure it would, but thought I'd ask anyway)?

Any thoughts/comments/shared experiences much appreciated.

Cheers

John
Triumph TR7 FHC, 1977
http://t-r-7.blogspot.co.uk

saabfast
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Re: Gearbox /clutch issues

Postby saabfast » 04 Jan 2021 22:48

It does sound as if there is something amiss with the clutch. I am not that familiar with the 4 speed but are you sure the friction plate is in the right way around? Otherwise it could be something in the arm (worn at the pivot if it is like the 5 speed) or the thrust bearing not square/properly inserted. At least the 4 speed is lighter and easier to remove for a look than the 5 speed! Was the flywheel nose bearing changed? Did the gearbox work OK pre fitting with no binding? Crank end float could be roughly checked by just levering the front pully to see if there is much movement (not very scientific but could show if it is very bad).
Alan
Saab 9-5 2.3t Vector Auto Estate Stage 1
Saab 9-3 2.0 SE Turbo Convertible
'81 TR7 DHC
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johnnyj
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Re: Gearbox /clutch issues

Postby johnnyj » 04 Jan 2021 23:06

Hi Alan and thanks for the info. The gearbox is the original one to the car and was working fine when removed. It was then stored for about 20 years, but checked over and the oil and seals replaced before re-fitting. Friction plate, yes, it is the right way round (I even took the bell housing off again and re-checked before mating it to the engine, just to be sure!). I didn't change the nose bearing/spiggot bush and probably should have done. I'll have a look tomorrow at the approx level of crank movement tomorrow. Thanks again.

John
Triumph TR7 FHC, 1977
http://t-r-7.blogspot.co.uk

busheytrader
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Re: Gearbox /clutch issues

Postby busheytrader » 05 Jan 2021 03:14

a mate’s Spitfire had the same issue many years ago.

The advice he had from an old school garage was “it’s either the clutch release bearing or spigot bearing that are knackered or both! You have to open up the bell housing for both so you might as well replace both”

johnnyj
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Re: Gearbox /clutch issues

Postby johnnyj » 08 Jan 2021 22:02

Quick update on this one. I decided to go for the clutch release/throwout bearing theory, so removed the gearbox in situ for a look. Got the box/bell housing on the bench, took off the bearing and it was very noisy and scored, with lots of evidence of heat build-up. Curious. Why had it happened?

Time to fess up - I had installed it backwards on the carrier. What an idiot! No wonder it was knackered.

A quick call to Robsport got a new one the next day, in it went, everything back together...lovely clutch operation and gear changes. Result. There's a moral to this story somewhere...

Thanks for all your help, advice and encouragement, as ever.

John
Triumph TR7 FHC, 1977
http://t-r-7.blogspot.co.uk

saabfast
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Re: Gearbox /clutch issues

Postby saabfast » 09 Jan 2021 12:25

Good to know it was not an engine problem and was easily solved.
I often get it all back together and then have doubts I have put it all back the right way around. I think it an age thing in my case, memory fading! :roll:
Alan
Saab 9-5 2.3t Vector Auto Estate Stage 1
Saab 9-3 2.0 SE Turbo Convertible
'81 TR7 DHC
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FI Spyder
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Re: Gearbox /clutch issues

Postby FI Spyder » 09 Jan 2021 14:44

Carpenter: measure twice, cut once.

Mechanic: Check assembly twice, button it up once.
- - -TR7 Spider - - - 1978 Spitfire- - - - 1976 Spitfire - - 1988 Tercel 4X4 - Kali on Integra - 2013 Volt - Yellow TCT

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