Technical Sticky Gear Selection

[Mercky]

Hi All

Over the past few days I've noticed my gear selection has got a bit stiff and it also crunches while selecting reverse, car is a 2014 TA and has 77,000 miles. Is this likely to be the clutch on the wayout or a selector problem? Thanks

 

[John202020]

How is it engine off?

 

[Mercky]

How is it engine off?

seems fine with engine off, or at least better, obviously no crunch in reverse, seems to point at clutch/slave cylinder? I had been wondering about the clutch recently as pedal feels a bit soggy

 

[John202020]

Twin air reverse has always been noisy though not crunchy if clutch hydraulic then try bleeding the system first?

 

[jrkitching]

Clutch hydraulics has to be the prime suspect, followed by the clutch itself.

 

[Mercky]

Clutch hydraulics has to be the prime suspect, followed by the clutch itself.

Thanks, an interesting observation this morning - started up car from cold and everything fine, went for a 3 mile drive stopping half way to check reverse and all still fine but as I approached home I noticed the gear change getting sticky again and when I got home it would not engage reverse. So if it's temp related does this suggest gearbox oil? I cant see the hydraulics changing on warm up but maybe I'm wrong? Could it still be the clutch itself?

 

[John202020]

Our 1.2 last year suddenly decided you couldn't select reverse at all, over time we now can but there's still something not right as the stick won't spring left once out of the gate

 

[Ralf S.]

when I got home it would not engage reverse. So if it's temp related does this suggest gearbox oil?

No. Gearbox oil (or lack of it) does not stop the gears engaging. It only prevents the gearbox components wearing out.

Garages always suggest "change the gear oil" as a catch-all suggestion but I've lost track of the number of times an OP writes... "....the garage changed the gearbox oil...." and "... it was better for a while..." and ".. but now it's the same as it was before..." all in the same post.

I cant see the hydraulics changing on warm up but maybe I'm wrong?

You're right. However the slave cylinder is sitting on top of the gearbox, which is hot.. so it will get warm and that will affect the push-rod and the seals. Even without a slave, the internal gearbox/clutch parts do get hot so the clearances within the clutch and gearbox are different when it's all warmed up, which might affect how easy the gears are to shift.

Could it still be the clutch itself?

Yes it could.. Worn out clutch plates are more likely to have problems not slipping, rather than not disengaging the drive... but.. the slave activates the clutch by rotating a forked arm inside the clutch bell-housing that presses a release bearing against the clutch pressure plate, which disengages the clutch. After a while the bearing body starts to wear a groove into the pressure plate fingers, so that when the forked arm pushes it, some of the movement is not transferred to the clutch pressure plate because the groove introduces "slack" into a chain of what should be just/barely touching parts.

You can also get wear of the forked arm and/or wear of the bearing body itself.. but the bearing and pressure plate fingers are the softer parts so they're more likely to wear out... They both come in the same clutch kit, so there's no point trying to work out which one of them is the main culprit.. by the time you get this far in the dismantling, just replace both of them regardless.

Clutch hydraulics has to be the prime suspect, followed by the clutch itself.

The best clue to the cause is to listen to the engine while it's idling. Get your head under the bonnet.. If you can hear a scraping sound like shhhick shhhick, shhhick... etc. get someone to press the clutch pedal in. If the noise quietens down, then that's the release bearing (you will need a new clutch kit). If the gearbox/clutch are relatively silent and don't make any more or less noise when the pedal is pressed, then it's more likely to be the slave cylinder.

Ralf S.

 

[Mercky]

No. Gearbox oil (or lack of it) does not stop the gears engaging. It only prevents the gearbox components wearing out.

Garages always suggest "change the gear oil" as a catch-all suggestion but I've lost track of the number of times an OP writes... "....the garage changed the gearbox oil...." and "... it was better for a while..." and ".. but now it's the same as it was before..." all in the same post.



You're right. However the slave cylinder is sitting on top of the gearbox, which is hot.. so it will get warm and that will affect the push-rod and the seals. Even without a slave, the internal gearbox/clutch parts do get hot so the clearances within the clutch and gearbox are different when it's all warmed up, which might affect how easy the gears are to shift.


Yes it could.. Worn out clutch plates are more likely to have problems not slipping, rather than not disengaging the drive... but.. the slave activates the clutch by rotating a forked arm inside the clutch bell-housing that presses a release bearing against the clutch pressure plate, which disengages the clutch. After a while the bearing body starts to wear a groove into the pressure plate fingers, so that when the forked arm pushes it, some of the movement is not transferred to the clutch pressure plate because the groove introduces "slack" into a chain of what should be just/barely touching parts.

You can also get wear of the forked arm and/or wear of the bearing body itself.. but the bearing and pressure plate fingers are the softer parts so they're more likely to wear out... They both come in the same clutch kit, so there's no point trying to work out which one of them is the main culprit.. by the time you get this far in the dismantling, just replace both of them regardless.


The best clue to the cause is to listen to the engine while it's idling. Get your head under the bonnet.. If you can hear a scraping sound like shhhick shhhick, shhhick... etc. get someone to press the clutch pedal in. If the noise quietens down, then that's the release bearing (you will need a new clutch kit). If the gearbox/clutch are relatively silent and don't make any more or less noise when the pedal is pressed, then it's more likely to be the slave cylinder.

Ralf S.

cheers for that - very helpful. I'm not sure I'd hear the 'shhhick' noise with the clatter of the TA but I'll give it a go! I was looking at Youtube videos of clutch replacement and was surprised how involved and labour intensive it is, wont be cheap I suspect.

 

[Mercky]

Have made some enquiries and will be having a new clutch fitted. From reading the forum I'm concerned I should also be replacing the DMF, can anyone advise? Could the current symptoms actually be the DMF and not the clutch?

 

[Ralf S.]

Have made some enquiries and will be having a new clutch fitted. From reading the forum I'm concerned I should also be replacing the DMF, can anyone advise? Could the current symptoms actually be the DMF and not the clutch?

The DMF usually makes a grinding noise and gives you driveline shunt when it's starting to get worn. If your car drives quietly and doesn't shunt excessively then the DMF should be okay.

If your car has had a clutch before, I would change the DMF, otherwise it would be a PITA if that failed in a few months time when you've just finished paying off the clutch replacement work.

It's a Universal Rule that DMFs last around 1.5 times as long as a clutch... you just know. Cars are devious...


Ralf S.

 

[Mercky]

The DMF usually makes a grinding noise and gives you driveline shunt when it's starting to get worn. If your car drives quietly and doesn't shunt excessively then the DMF should be okay.

If your car has had a clutch before, I would change the DMF, otherwise it would be a PITA if that failed in a few months time when you've just finished paying off the clutch replacement work.

It's a Universal Rule that DMFs last around 1.5 times as long as a clutch... you just know. Cars are devious...


Ralf S.

I'm getting a new DMF also, not cheap, the entire job is now coming in well over a grand, dident want to take the risk with the DMF as I may well hang on to the car for a few years.

 

[Mercky]

An update for the record, just had the clutch, DMF and slave cylinder replaced by an Indie and car driving like new, it's surprising how light a new clutch is! Decided to change the DMF as a precautionary, although it was fairly pricey it seemed the wise thing to do, slave cylinder was cheap enough and again seemed a sensible move while everything was stripped. Will do an oil / filter change myself this week and also change the Iridium plugs as they have about 55k on them now. Suspension will be next!!