Semi auto gearbox won't change up when accelerating...

[Kerry9]

Dear Funsters,

My Mercedes 2.7 semi-auto transmission won't change up as I accelerate, or change down on decelerating. Until the journey home today it has worked as it should do since we bought the motorhome last year.

I had to nurse it home this weekend from by flicking the gearstick out of auto, into neutral, then back into auto and it would then engage the correct gear for the speed. It amnually engages first, and reverse no issues, and stays in neutral when it should.

A new Mercedes flywheel and clutch system was fitted by Mercedes under previous ownership about two years ago, so these have done less than 2000 miles.

No smells, no noises, no warning lights on the way home.

On reaching home I ckecked the clutch reservoir which is just below the maximum fill level.

Could anyone advise what might be the cause of this problem? Could it be low transmission oil levels? (No drips or stains under the vehicle suggesting any leakages.)

Thanks in advance for any advice and suggestions.

 

[Odd-no-more]

I can't help with your system, but on the one I had on a transit all the faults were electronic. Sometimes it would loose a gear going for second to forth. Always sorted itself out by turning it off and back on after 5 minutes. If you have tried this then maybe a gearbox ECU reset may help. I think that is a dealer's job. Good luck

 

[Figaro]

Gearbox oil level ?

 

[tinks703]

Have a look at merc van web sites and see if you can identify the problem and how to sort it.

 

[Podney]

If you can check gearbox oil level,that’s a start.
A Mercedes car I had a few years ago never had the gearbox oil checked by main dealer,and this was only discovered by a specialist merc garage when the car was about five years old.

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[TheBig1]

at a guess, and it is a guess, gearbox speed sensor input to gearbox ecu

 

[Sundowners]

Have you tried disconnecting the battery for a few minutes to reset it????? Providing disconnecting it doesn't create other issues??!!!!!!---------- the only issues I have had with auto are electrinic--------- reset fixed it for a while and low oil-------i eventually fixed the electronic fault by getting new battery connections soldered on!!!!
Have you moved any wiring???? The cables to the transmission control may be picking up stray signals------ sounds stupid but a common fault on certain years of Dodge Ram autos!!!!!!! I screened the main cable from alternater with tin foil---- that helped but not100%

 

[jezport]

Have you tried disconnecting the battery for a few minutes to reset it????? Providing disconnecting it doesn't create other issues??

Had an issue on a ford auto box, disconnecting the battery sorted it. Fault never came back, owned it further 3 years.