E320cdi gearbox problems

[dave w]

Hi, guys and girls my E320 cdi(2000) series gearbox is behaving quite strangely? On a 400 mile round trip last friday the car kept changing down to fourth gear on the motorway even though I was making no input to make this happen. The car then stayed in fourth until I 'tipped' it up to fifth but even when trying to tip it up the response was not immediate. I know it is normal for the car to change gear automatically but this is out of the ordinary, this would happen holding a steady 70 on a flat road surface. I had fluid and filter changed 4k ago, have had car plugged in on star computer and no faults logged. The car has covered 134K and am concerned this is going to be a big bill. Nearest independant says could be speed sensor in gearbox, what sort of job is this to achieve (£) and is there anything I can check DIY before I book the car in? Any advice appreiciated.

 

[stewie07]

Sorry to resurrect an old thread but this is exactly the symptoms I am experiencing with my 320 cdi. Did you ever resolve it?

 

[Naraic]

He was last here in August 2007.

 

[television]

Speed sensor normally stop the car shifting from the lower gears, sticking valve in the valve body, has the fluid ever been changed as this could cause the problem, we now like to change the fluid every 40k miles

 

[stewie07]

I have changed the fluid and filter about 1000 miles ago, the fluid that came out was red and looked almost new. In a twist to the tale I have a way to resolve the change down by flicking on the cruise, this immediately drops it back into 5th.
It seems that if the car goes over say 75mph when you slow down by throttling off as soon as the speed drops below 65 - 70 it changes down to 4th, the only way it will change back to 5th is if you knock it over on the selector or flick on the cruise, even if you accelerate with speed rising to over 100mph it still wont change back up on its own.
Also if you have the cruise on at 75 and you flick it off to slow down it slows down normally and won't cog down.
I've read the codes with my own c4 and there are no faults, I've changed the throttle position sender & the EGS controller and still it does it.

 

[stewie07]

Yesterday I tried changing the turn rate sensor under the rear seat, still no change. I have a couple of untested 722.6 boxes at work I might try swapping out the electrics pack. One thing I was curious about was are the valve bodies the same in all the 722.6 boxes?

 

[markheaney2]

i had this problem once on my 2000 e320 cdi when i had mis matched tyres on the car they were all the same size but upon inspection had slightly different rolling ratios new tyres sorted it out

 

[stewie07]

I think the thing keeps me thinking its electrical is the fact that when I use the cruise control all gear changing is normal

 

[Steve@Avantgarde]

I would advise getting it onto STAR diagnosis and getting the codes read but it is likely a electro plate issue.