Gear selection troubleshooting

[Spider]

Can I suggest first measuring how far the Backing Plate moves on Clutch operation ? You can do that by opening the Timing Cover Inspection Hole, rotating the engine over until a backing plate bolt head appears in the window. I do it with a 6" rule. Have someone operate the Clutch pedal and see how far that bolt head moves. You need about 1.0 mm. At 0.8, you'll just get enough disengagement. When everything's in perfect condition, you'll get around 1.5 mm.

An often over looked 'stopper' is the circlip in the Slave Cylinder. If everything looks right and you are getting limited travel, as a test only, remove the circlip and try again with the measurements. If this works, then there's likely still something worn in the lever mechanism. The other thing to check is the Pushrod, there was 2 lengths in these.

Also, when bleeding the clutch, be sure the Piston is pushed ALL the way in to the base of the Slave. Bleeding with it in any other position, it can (and usually does) hold some air as the bleed nipple is right over the hose inlet, but there is still a large cavity that holds air, to the side if the piston isn't pushed all the way back.

If you are getting 1.0 mm or more movement here, then I'd suggest the issue isn't with the clutch itself but the Primary Gear. It may well have been pinched under the Flywheel.

[mini_surfari]

Thanks Spider,

Yeah primary gear was removed on stripping.

I’ll do as you suggest and measure the back plates travel.

[360gts]

Oli, was the flywheel dismantled???
As I said earlier...suspicious of the primary gear and/or the plate itself.
Even though the pressure plate may be moving the required amount....if the plate is semi stuck on the primary gear....drive will still be there on the input gear.

Think it's time to jack up the RH side and remove the flywheel for inspection.
Just my opinion.

[mini_surfari]

Right,

Had a measure, and currently getting 2mm of travel using spiders method. With both the long and short push rods on.

So I’ve not bothered, fighting with the clutch arm split pin at the bottom, as I suspect you’re right, and the engine will be coming out to get the flywheel off.

Are you able to explain what you mean been by the primary gear being pinched under the clutch? I assume you mean the friction plate isn’t sliding properly on the splines to disengage?

[Spider]

Are you able to explain what you mean been by the primary gear being pinched under the clutch? I assume you mean the friction plate isn’t sliding properly on the splines to disengage?

Yes, sound to me like you are getting plenty of movement and disengagement there.

What I mean here in regards to the Primary Gear being pinched is under the right (wrong) circumstances, the Primary Gear is being pinched between the Flywheel and the thrust shoulder on the Crank, though, there can be other reasons for the Primary Gear not being able to free-wheel on the Crank Tail.

Some causes for the Gear being pinched in the way I'm suggesting are the end float is too tight, the thrust washer being fitted the wrong way around, the C Clip being dislodged as the flywheel is being fitted, a worn taper on the crank and / or flywheel (letting it seat too 'low' on the crank), though, there can be others, but I'd say it's somewhere around here you now need to look. It could also be binding of the Primary Gear on to the Crank Tail - has it had new bushes fitted in recent years ?

[mini_surfari]

Thanks for that, I’m with you.

The primary gear hasn’t been re-bushed, as it was in v good condition.

I’ll hopefully get some time to work on it over the bank holiday, so I’ll report back with my findings!


Currently sat pondering whether to do it in place or take the engine out.. that remote diff housing gives me the sweats taking it in and out

[mini_surfari]

Went with the engine out option!

Ok picture heavy post... other than marks in the primary gear bush, didn't find anything suspicious. Double checked end float, on the higher side of spec. Thrust washer in the correct way. There is wear on the clutch arm ball, but stated above, the clutch diaphragm has 2mm of travel when the pedal was depressed.

[360gts]

Well, the thot plickens!!!!


My first thoughts were...Aha...the primary gear....however, the pitting on the teeth is mostly NOT where the plate sits.
Guess we could ask if the plate slides back and forward nicely on the P. gear? It doesn't need much movement to free the drive.

The mystery seems to be that you say it worked well prior to the gasket strip down.

[Spider]

Cheers for the photos.

To Check if the Primary Gear was being pinched between the Flywheel and the Crank, you really need to check for that with the Flywheel on. I usually do this before fitting the Flywheel Housing. I'll drop the Flywheel on the Tail of the Crank (I'll have it in the engine stand, tail up) and with the Primary Gear all fitted up, make sure it spins free and there's plenty of end float. If it feels like there's limited end float, then I'll torque down the Flywheel and check again.

From your photos, what's going on in the centre of the hub ?

[mini_surfari]

Well, the thot plickens!!!!


My first thoughts were...Aha...the primary gear....however, the pitting on the teeth is mostly NOT where the plate sits.
Guess we could ask if the plate slides back and forward nicely on the P. gear? It doesn't need much movement to free the drive.

The mystery seems to be that you say it worked well prior to the gasket strip down.

Yep, clutch plate slides on the the primary gear nicely despite marks on the teeth.

[Spider]

Cheers for the photos.

To Check if the Primary Gear was being pinched between the Flywheel and the Crank, you really need to check for that with the Flywheel on. I usually do this before fitting the Flywheel Housing. I'll drop the Flywheel on the Tail of the Crank (I'll have it in the engine stand, tail up) and with the Primary Gear all fitted up, make sure it spins free and there's plenty of end float. If it feels like there's limited end float, then I'll torque down the Flywheel and check again.

From your photos, what's going on in the centre of the hub ?

Another check that comes to mind here too since the flywheel is off is to drop the C Clip, Backing Washer in to the Flywheel, then offer up the Primary Gear in to that, it might show up something.

[mini_surfari]

Cheers for the photos.

To Check if the Primary Gear was being pinched between the Flywheel and the Crank, you really need to check for that with the Flywheel on. I usually do this before fitting the Flywheel Housing. I'll drop the Flywheel on the Tail of the Crank (I'll have it in the engine stand, tail up) and with the Primary Gear all fitted up, make sure it spins free and there's plenty of end float. If it feels like there's limited end float, then I'll torque down the Flywheel and check again.

From your photos, what's going on in the centre of the hub ?

My old man’s wiped the flywheel over, that mark is just residual oil. Will post a picture when once I’m back on the computer,

Ah ok, so I suppose the potential is the flywheel is moving too far up the crank tail once it’s torqued up. Time to take the transfer case off then and check that.

Will also try the C- Clip test!

[Spider]

My old man’s wiped the flywheel over, that mark is just residual oil. Will post a picture when once I’m back on the computer,

OK, Gotya on the 'mark' on the flywheel hub.

Ah ok, so I suppose the potential is the flywheel is moving too far up the crank tail once it’s torqued up. Time to take the transfer case off then and check that.

And yes, thus 'pinching' the Primary Gear

[360gts]

My old man’s wiped the flywheel over, that mark is just residual oil. Will post a picture when once I’m back on the computer,

OK, Gotya on the 'mark' on the flywheel hub.

Ah ok, so I suppose the potential is the flywheel is moving too far up the crank tail once it’s torqued up. Time to take the transfer case off then and check that.

And yes, thus 'pinching' the Primary Gear

I keep going back to what was said at the beginning
"it was working well before I stripped it"
So what happened during the strip down that would cause this problem???

[Polarsilver]

IF my car & with nothing obvious at fault with the crank & primary gear end float check out ok .. i would buy a "reputable" New Clutch Plate make sure it free slides on the splines ..then set up the 3x spring steel drive strap packs with at least two drive straps per pack ( 3 off drive straps under each bolt if i had them )
Fit a new MS Clutch Arm & put it back together.

[360gts]

In addition to what Notman suggested....replace that primary gear as well....just as a future preventative measure.
As an engineer I am all about finding the source of a problem......always worried that if you put things back together without finding a problem.....keep wondering when it will come back to bite you. It usually does...and at the most inconvenient time and place.

There was one test I forgot to mention way back.....bit late now. Sorry.
Not sure if Oli jacked the van up and had it running with it in a gear....depress the clutch to see if the wheels slowed to a stop.

Guess we will all be waiting to hear the results when he puts it all back together.
Good luck.

[mini_surfari]

Had an hour spare earlier.

C clip and washer fit in the back of the flywheel no problems there. I put the flywheel back on the crank and torqued it down, then turned the engine over, and it’s not bound up on the flywheel as the primary gear remains stationary when turning over.

I was looking at new clutch plates for a ‘quality one’ last night, minispares do borg&beck, but I’m sure the one thats on it is AP…

What’s the idea of putting a 3rd drive strap on sorry?

As you say it’s very frustrating not being able to find the issue definitively, and even more so that no components from the clutch / gearbox were changed!

Thanks again for all the pointers so far everyone!

[Andrew1967]

NOS clutch plate here Oli ...

https://www.ebay.co.uk/itm/285789715998 ... SwUFVmBzla

[mini_surfari]

NOS clutch plate here Oli ...

https://www.ebay.co.uk/itm/285789715998 ... SwUFVmBzla

Thanks Andrew! Got to be better quality than what’s being turned out by some suppliers!?

[Polarsilver]

Can only speak for me.. i would get a "new" Clutch Plate & then with the flywheel taken off the crankshaft & placed flat on the Bench with the Clutch Friction Plate in position & look see how the drive straps sit ( with the bolt up the end secured on the Flywheel) ..they "may touch" onto the cast upstands on the pressure plate "or there may be a Gap" between the sets of spring steel Drive Straps & the upstand .. the idea is to shim or space these drive Straps so the Drive Straps just sit on-top of the pressure plate upstand without any sort of bending pre-loading. the drive Straps when bolted up are sort of in a neutral situation not bending by significant amount either up or down .. to add a 3rd Strap is advised ( by the Experts ) for competition use ..but me using ye-oldie Drive Straps think they might be a bit weak so i add the third.
Also seen some of my used Drive Straps that have material cracks so best check any that will be re-used.. keep at it ..will be good when your problem is solved .

Unrelated but my GT had poor clutch action did not slip it was just odd.. i could not see anything wrong other than when i looked the Friction Plate & it had a date printed on showing this clutch plate was 25 years old but it looked good to use .. a New Friction Plate supplied by MS transformed my Clutch