[shawn]

Would the incorrect grade of gearbox oil equate to bad gear changes in a 4 speed manual box on a Type 4?

The specified oil is SAE90 but when I bought some last year the motor factor informed me this was no longer available and supplied an 'equivalent'. I can't remember what this was now, unfortunatly.

Not sure if this is the reason for the problem, but I have fiddled with the gear selector and got that as near to perfect as I can with new bushes at the front end so I don't think is the problem especially when you take into account it changes gear very well when cold but after a run of 10+ miles the gears seem to get harder to find with 1st and 2nd being the worst affected.

I'm wondering if it is the oil getting to thin and somehow interferring with the gear change? If not that could it be a clutch problem???

[Andy]

The wrong oil can effect it yes (generally) , probably this is the reason if its effected by temperature (as you say it gets worse when it gets warm)

Having said that, heat expansion could cause other things.

You can check if its the clutch dragging without too much trouble.


Do this with a cold engine then again when its hot after a run.

Clutch down, select reverse (as this has no synchro). Take it out of gear and try it again, this time don't press the clutch in quite as much (ideally about 5mm less) , remember to just very gently try to select, stop if there is any noise!

If its ok, repeat this a couple of times to find the point where you cannot engage it. (If you are careful you can use reverse for this, I do as it's the easy choice for this test, due to the potential noise)

If you find its different when hot / cold, it does point to a clutch issue normally. You should be able to select it with the pedal not fully (5mm less) depressed as this would be a decent clearance, but you are looking for differences with the engine / box hot and cold.

Assuming you have the clutch adjusted properly ?

[shawn]

The clutch is a hydraulic one on the Type 4 so not sure if it can be adjusted?

However, I'll try the reverse idea when I go out in it next and see what happens.

Cheers Andy

[Andy]

Oh I did not know that , I assumed it was cable.

Unlikely to have much if any adjustment on a hydraulic one (maybe pushrod adjustment but that's best left alone)

It "could" be dragging to to a failing clutch slave (more likely) or clutch master cylinder (not too likely)

If you do the idea I put above, (you get what I was trying to say) to see if that changes with temperature much.

It may be worth changing the clutch fluid too if its easy to do, although care needs to be taken to make sure you still have a functioning clutch afterwards. If I was doing this, I would not pump the pedal, just crack the slave cylinder bleed nipple open (with a length of tube on it) and let some fluid run out (keeping the master cylinder topped up), then tighten it after I had got about 250ml out. Gravity should do the work for you, it may take time (this only works when they "work" anyway, not a good method for an empty one) , at your own risk though as I am not familiar with T4's , although I have done this on an ancient BMW I owned for a while, with 100% success.

[shawn]

The clutch uses the same resovoir as the brake fluid, so I'll leave alone unless I need to touch it.

If I get chance this week I'll try and speak to the Terry's at Volksfarmers, what they don't know about Type 4s isn't worth knowing.

[Andy]

OK

Would be interesting to know the outcome etc.

[shawn]

I've spoken to Jane at Volksfarmers (a font of all knowledge Type 4 related) and she thinks it sounds very much like air in the clutch hydraulic system as ususally these gearboxes are very tough. She reckons it is possible a dodgy seal on either of the cylinders may be drawing air into the system or possibly one of the cylinders is dying. In some ways she thinks it is cheaper for a replacement gearbox than the master and/or slave cylinder!

Rather than mess about trying to do it here, I'm going to kill two birds with one stone and pop over to Ashford at the weekend so Volksfarmers (where they have replacement parts) can diagnose and hopefully fix the problem and then visit my brother afterwards.

[Andy]

shawn, on 22 Apr 2009, 04:06 PM, said:

Rather than mess about trying to do it here, I'm going to kill two birds with one stone and pop over to Ashford at the weekend so Volksfarmers (where they have replacement parts) can diagnose and hopefully fix the problem and then visit my brother afterwards.

Sounds like a good plan

Pain to change those seals (generally) anyway. I did the master cyl on a BMW years ago (new seal kit) and it was not too pleasant a job to do (more mess and trying not to snap the o-rings as you stretch them over the piston etc)

Let us know what they find anyway

[shawn]

The good news is the clutch seems to be working correctly

However the bad news is that there is almost a definite fault with the internals of the gearbox that is manifesting itself in difficulty changing down to second and finding first when stationary and an ominous rumble that I had tuned out as one often tends to do when you drive a car so frequently.

Fortunatly they have a few good gearboxes laying around.

Whilst the engine is out they will also check and replace the gear box, clutch, thrust bearing, slave cylinder as required for the grand total, in a worse case that all these need changing, of £400. I thought this is a reasonable price so just need to make it through the next couple of months to save the pennies for the work.

[Andy]

Good to hear the clutch appears to be ok now.

The problem (difficult changing especially down, does initially point towards a clutch issue) , but you've had that checked to it can only be internal.

Having looked at what they are going to replace (I'm guessing this is parts and labour) the price does look quite reasonable in my eyes , bearing in mind as you say, that's the "worst case" scenario.

It's good of them to give you that price ( and its a very good sign of honesty ) rather than have to bump the price up halfway through due to something unexpected.

I know what you meant about tuning (ie: learning to ignore as you hear them so frequently) noises out