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[bestseany]

I have a theory about my gearbox problems and just wanted an opinion about it.

Just to recap, when my gearbox gets warm it can start getting clunky when changing down a gear and occasionally it will kick down a gear on its own if I hold the revs at certain point and I have to move the selector to '3' and back to 'D' to recover from it, otherwise "Automatic Gearbox" will show on the MID.

The past few weeks I've noticed that the drivers side front cooling fan is really noisy. It's squealing really badly, like it's rubbing on something or the bearings are going. I notice that the fan is on the same side as the transmission cooling pipes go into the radiator.

My theory is, if the fan isn't working properly and isn't cooling the gearbox fluid correctly, would that cause my problems? I'm probably way off here like.  

[Markjay]

The cooling fans only work when stationary or in slow traffic, not on motorway speed etc, so if the auto gearbox problem persists when driving in the open then the fan is probably not the cause...

[bestseany]

The gearbox only seems to kickdown and get clunky after coming off the motorway after a long drive or lots of stop/start driving in traffic, i.e. when it gets warm and there isn't as much airflow.

I know when it's about to do it as it holds onto the gear for too long just before it kicks down, but only seems to happen when driving slower, and if I accelerate or let off the pedal completely, it will clunk and then carry on as noraml. I think it does it either in 2nd or 3rd gear, so on the motorway the problem never occurs.

I've been told it could the valve block or the clutch bands in the box, but I wanted to check if it could be something as simple (and cheap!) as the fan that's causing it.  :-?

I was thinking about it being the selector switch, as the odd LED will flicker when putting it drive when I first start it in the morning (although not after driving for a bit), but I can't see how that would only cause it after the box has warmed up.

[bestseany]

Anyone?  :-/

[SteveD]

Have you tried replacing the oil & filter (both sumps worth of oil)? It sounds like your problems only occur when the oil is hot - which is when it's most likely to break down if it's contaminated.

I did mine for the hell of it and it was like a new box after about 100 miles. The new oil seemed to flush out all the valves and made the changes really smooth. It also made kickdown happen a lot faster and smoother.

[bestseany]

Have you tried replacing the oil & filter (both sumps worth of oil)? It sounds like your problems only occur when the oil is hot - which is when it's most likely to break down if it's contaminated.

I did mine for the hell of it and it was like a new box after about 100 miles. The new oil seemed to flush out all the valves and made the changes really smooth. It also made kickdown happen a lot faster and smoother.

Yep, the gearbox fluid and filter were the first thing I changed mate. I've done about 3000 miles on the new fluid now.

[Marks DTM Calib]

Classic valve block fault.....

[bestseany]

Classic valve block fault.....

What would need to be done to fix it?