2.5 16V Auto gearbox acceleration prob.

[Merc30]

Hi.

I've got a 2.5 16v Auto which has developed a problem regarding the gearbox.

When I accelerate from a standing start, the car initially starts to go and within a few seconds slips into neutral and then a couple of seconds later slips back into gear and drives fine until I halt at lights etc and the same thing happens again.

Does anyone know what could be causing this? is there some sort of electronic selector that could be the problem rather than the actual gearbox?

Let me know if you've come across this problem before.

Cheers.

 

[Dieselman]

Your car uses a purely hydraulic gearbox, so no electronics.
The likely causes are either the ATF is low or the gearbox is trying to change into 1st gear but either cant engage it or 1st gear has gone AWOL.

 

[redbaron]

As DM says, A trip to your local specialist to check ATF level and a change to fresh ATF would be step 1.

 

[Will]

Could be worth checking the engine and gearbox mounts also. The 16v engine tends to move around a fair bit when revved hard on worn mounts. As the selector is fixed to the bodyshell, it could be enough to pop it in-out of gear?

 

[grober]

Sounds as if you might have a B2 piston problem. The (infamous) B2 Piston the problem was supposed to be fixed in later transmissions but the jury is out on that one. An auto transmission specialist [ who ideally should be familiar with these MB 4speed hydraulic boxes in particular!!] should be able to confirm/diagnose.

this is how to do it on another car- think you would have to drop the transmission in a 190 - if indeed this is the problem. http://www.dieselgiant.com/Mercedesb2pistonsealreplacementl.htm

 

[Merc30]

Thanks for the replies.

Fluid levels have been checked, all in order.

Will - I don't suspect engine mounts. Had them checked out recently.

Dieselman - If that's the problem, I take it the gearbox needs to come out and be opened up?. Surely it is finding first gear though because initially the car starts off ok, then it seems to slip out of gear because the engine just revs. Only lasts 2 seconds and slips back into gear.

Grober - sounds interesting, I'll look further into it.


It's a real pain because it means I can't cut into traffic or beat a Fiat 127 at the lights.

 

[Will]

If you get stuck, I know a guy who has a spare 2.5-16 autobox. They are specific to the 16v model and very difficult to locate secondhand.

Will