TD5 Auto unexpected kickdowns

Hi all,
so, I have this maybe odd issue with the automatic box in the TD5. Basically, I can be driving at a constant pace or a slight acceleration, and the box will drop down a gear when it really shouldn't do.
Normally I lift the throttle, it goes back to the original gear and I can put the power on again. It's odd.

A couple of times it's dropped down and I gave it a bit of throttle in frustration, there's a heavy clunk in the transmission and the auto box goes into limp mode with the lights flashing.

Any ideas?!

could be a solenoid failure... the shortest way is to read the fault codes from transmission ECU ... a filter and oil change before that would be good to start with a 'clean page' in this area

Loco said:

Hi all,
so, I have this maybe odd issue with the automatic box in the TD5. Basically, I can be driving at a constant pace or a slight acceleration, and the box will drop down a gear when it really shouldn't do.
Normally I lift the throttle, it goes back to the original gear and I can put the power on again. It's odd.

A couple of times it's dropped down and I gave it a bit of throttle in frustration, there's a heavy clunk in the transmission and the auto box goes into limp mode with the lights flashing.

Any ideas?!

Click to expand...

It would be helpful to know what speeds this behaviour occurs?

It had a change of transmission oil & filter maybe 3,000 miles ago, so still pretty fresh.
The speeds are relatively low, maybe 30-40mph up a very slight hill, not sweating it with the engine at maybe 2,200rpm (it's TD5) and not struggling, then it'll jump down pretty unexpectedly. You let off the power, it'll change back up, then you can continue as it was before. Really odd. Sometimes as I say, if the revs climb it clunks quite harshly and goes to limp mode (happened maybe twice now).

Probably unrelated, but sometimes when just starting the car from absolute cold, if I go from reverse to forward quickly it drops into limp mode. This doesn't happen when it's warm, however.

I'm crossing my fingers it's not a transmission out/rebuild issue!!

Loco said:

It had a change of transmission oil & filter maybe 3,000 miles ago, so still pretty fresh.
The speeds are relatively low, maybe 30-40mph up a very slight hill, not sweating it with the engine at maybe 2,200rpm (it's TD5) and not struggling, then it'll jump down pretty unexpectedly. You let off the power, it'll change back up, then you can continue as it was before. Really odd. Sometimes as I say, if the revs climb it clunks quite harshly and goes to limp mode (happened maybe twice now).

Probably unrelated, but sometimes when just starting the car from absolute cold, if I go from reverse to forward quickly it drops into limp mode. This doesn't happen when it's warm, however.

I'm crossing my fingers it's not a transmission out/rebuild issue!!

Click to expand...

On cars with any form of electronic control, like TD5 auto, battery condition is crucial. So the first thing I would be doing is checking the voltage of the battery WITHOUT starting the engine - best done first thing in the morning when the weather is cold and the battery has been standing overnight.

Just in case you're not used to doing it, here's a "how to":

1. Get hold of a multi-meter and set it to a low voltage such as 20 volts

2. There will be two leads - one red and one black - place the red one on the positive (red cable) battery post and the black one on the negative/black cable and wait until the reading has reached it's maximum (3-5 secs).

This will give the 'standing charge'. If it is below 12.5volts, your battery is low and needs charging. Once it has been charged for at least 12hrs, test drive the vehicle.

If the lights come on again, it is likely the fault lies elsewhere.


Dave

OK, I'll check it out. I think the battery is on its way out though. You turn the lights on and there's a notable dip before the alternator makes up for it. Also, there's a crust of acid coming from one of the terminals. The engine cranks well each time though, so didn't see an immediate need to swap out the battery just yet.

This wouldn't be the cause of the random kick-downs though, would it?

Loco said:

OK, I'll check it out. I think the battery is on its way out though. You turn the lights on and there's a notable dip before the alternator makes up for it. Also, there's a crust of acid coming from one of the terminals. The engine cranks well each time though, so didn't see an immediate need to swap out the battery just yet.

This wouldn't be the cause of the random kick-downs though, would it?

Click to expand...

It's important to understand why battery condition is critical in modern cars.

Imagine that you are about to start your car first thing in the morning after a cold night.

Due to their chemical nature, batteries cannot give out their maximum in cold temps.

So now we attempt to start the car by turning the motor, at this time large amount of battery power are sucked out to feed the start motor. This substantial drain does not leave sufficient 'juice' to supply all the various ECU's in the car so one or more of them throws up error codes and this is exactly what is happening when the M&S lights light when firing up the motor.

From how you describe the battery terminals, it sounds like you have further problems with the battery being able to deliver reliable electrical supply.

My advice? Remove the cables, Clean the battery terminals and charge the battery - then see if it's fixed the problem.

Good luck

Dave