P38A Gearbox Kickdown stopped working...

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MrGorsky

MrGorsky

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Location
Buckinghamshire.
Hello All,

I've tried to search for posts on this, but I keep getting an error message and it's not working.
Basically after years of trouble-free gearboxing, my car's gearbox has lost it's kickdown.
She drives fine in all other respects, perhaps the gearchanges are a little rougher than they were, but only under hard accelleration.

If I floor the throttle the car just sits in the gear it's in, even if going up steep hills. It will however kickdown if whilst going up a hill the speed drops to very slow and the gearbox selects what I would say is the right gear for the speed.

An ideas? I've read the fault codes and there are no faults logged.
If I change down using the gear lever then it changes down no problem.
 
Whats the oil like?

When was it last changed?

Mine was like that, it would hold onto 4th until 20mph :rolleyes:
new oil and a good run sorted it,
 
Henry_b said:
Whats the oil like?

When was it last changed?

Mine was like that, it would hold onto 4th until 20mph :rolleyes:
new oil and a good run sorted it,
Click to expand...

It was given a full service Feb last year. All fluids changed. I'm pretty regular with the servicing so the gearbox fluid is pretty clean usually. It gets done every two years. Engine oil every year. But I have to top up the engine oil a lot because she leaks!!

I have had a "gearbox overheat" message a bit lately, but it's the sensor, not the gearbox overheating. And it hasn't done that for a while now. I thought I might be in a "limp home mode" because of it, but the Nanocom shows no faults.
 
MrGorsky said:
It was given a full service Feb last year. All fluids changed. I'm pretty regular with the servicing so the gearbox fluid is pretty clean usually. It gets done every two years. Engine oil every year. But I have to top up the engine oil a lot because she leaks!!

I have had a "gearbox overheat" message a bit lately, but it's the sensor, not the gearbox overheating. And it hasn't done that for a while now. I thought I might be in a "limp home mode" because of it, but the Nanocom shows no faults.
Click to expand...

is it any different in sport mode?
 
I use to have the gearbox fault frequently when I lived in Zomerzet, turned out to be a bad contact with the sensor on the rad, cleaned the surfaces and all was peaceful...….
 
Henry_b said:
is it any different in sport mode?
Click to expand...
No. Does expactly the same thing in both modes.

The battery is fine, and the overheat sensor is due attention when the weather is more clement!

I'll have a look at the throttle cable adjustment (it's pretty tight without an play, but I'll check it) and the kickdown switch....
 
For future reference I have solved this kick down issue.

There is no kick down switch or cable on the gearbox, kick down is initiated when the ECU decides engine load, throttle position, and road speed etc demand it.

I lost kick down with no fault codes logged, but over time the engine started to run rough, and I lost power and all sorts of other symptoms. Turns out my throttle position sensor was bad. Its should read about 0.5 volts at idle rising to around 4.5 volts at WOT, but mine was nowhere near this. Changed it for a used eBay replacement (£20) and everything is fine again, Kick down is restored!
 
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