'98 C250 DT tranny acting up.

[neilrr]

The transmission in my recent purchase, a 1998 W202 C250 Diesel Turbo automatic, is starting to act up.

Very occasionally it feels like it's trying to pull away from a stop in much too high a gear. Also, v. occasionally after brisk acceleration it will hang onto a lower gear far too long & be reluctant to change up after I've eased off the accelerator or even taken my foot off it completely & coasted.

Had it on a Star yesterday & there are no g/b faults showing, ATF level was good. ATF was changed in July '07, 42K miles ago, when a new transmission control unit (026 545 91 32) was also installed.

What does this sound like?

TIA.

 

[clk208]

Very occasionally it feels like it's trying to pull away from a stop in much too high a gear.

"W" mode engaging when not selected - dodgy switch? When my dad had a W202 C240 that used to sound very strained pulling away from a standing start in 2nd (W mode), particularly as it seems to be a fairly tall gear that will probably hit getting on for 60mph.

My W208 320 manages it just fine but not sure I would want to use this regularly with one of the lower powered engines.

 

[neilrr]

Unfortunately it does it in both modes.

 

[BlackC55]

Did you check any of the gearbox live data or adaptation values? Drop the sump pan too and check the filter is not blocked or any metal in the pan.

 

[neilrr]

The car is going back in on Wednesday. I'll update then.

 

[neilrr]

Well, had the car in for another check a couple of days ago when it was on the Star machine for a delve around.

There is apparently nothing wrong with the gearbox. He checked the adaptation values, erased any old faults, checked the ECU, temperature, flavour & did whatever else one does when a Star machine is plugged in & one is trying to find the cause of a problem.

He thought it might be engine related with something not telling the engine when to spool up the turbo (I think) or not telling the tranny info that would help it select the correct gear but the Star investigation revealed nothing.

I suppose the next thing would be an ATF & filter change, even though a Mercedes dealer did this 42K ago.

One thing which I forgot to mention to him (duh!) was on the PRNDL sometimes when it's in drive the light on the shifter isn't illuminated unless I give it a nudge into a position where the light comes on & all the time the reversing lights do not come on when in reverse unless I physically move the wand over a little bit & hold it in that position. I know (think) this stuff is all electronic but I wonder if it's possible this issue with the shifter has something to do with it.

Thoughts from the panel most welcome.

EDIT: Just saw a thread where someone mentioned speed sensor issues. Could that have anything to do with it? I'd have thought that would have shown up on the Star interrogation.

 

[tim.100]

Also, v. occasionally after brisk acceleration it will hang onto a lower gear far too long & be reluctant to change up after I've eased off the accelerator or even taken my foot off it completely & coasted.

Mine does that too - and has since new. But only for a second, or maybe two. Don't forget that it has adaptive electronics that try to adjust to your driving style.

On the other issue I can't comment.

 

[BlackC55]

Have a look at the engine mounts.

 

[Dieselman]

Very occasionally it feels like it's trying to pull away from a stop in much too high a gear. Also, v. occasionally after brisk acceleration it will hang onto a lower gear far too long & be reluctant to change up after I've eased off the accelerator or even taken my foot off it completely & coasted.

Unlike a mechanically controlled gearbox, lifting off won't make the gearbox change up.

I would check out the selector switch as it may be selecting an implausible position, but that should show on STAR.

 

[neilrr]

I haven't been using this car hardly at all so have had nothing to report back on.

It's going in this week to go on the hoist for a look at the engine mounts & all the rest underneath. Thanks for the suggestion.

It did go back on the Star machine to investigate whether there was something up with the gear selector ECU & nothing wrong was found.

I drove it last night, a 30 mile motor way trip & then 30 much slower stop/start miles in suburban traffic. It frequently showed its two problems - it feels like it's trying to pull away from a stop in much too high a gear & it will hang onto a lower gear far too long & be reluctant to change up.

I tried manually shifting down into 1st or 2nd when it felt like it was stuck in too high a gear on take off from a stop but this made no difference at all. What did make a difference was putting it in P then back into D. After doing that it would start off the line in the correct gear.

Any ideas?

 

[neilrr]

Well, I wasn't really using this car while driving the 190E 2.6 I sold the other day so did no more on investigating the auto box fault.

With the W201 gone I took the C250 TD into Star Motors in Caversham where we had a really good look around the underneath & couldn't see anything wrong. In fact, the underside of the car is in very good condition & everything is as it should be.

I decided to get the ATF & filter changed while it was there. Strangely, while looking at the ATF on the dipstick it was red, coming out of the box it was nearly black.

The fluid change seems to have cured the problem & you'd hardly know it had a gearbox now, so smooth are the changes. Another benefit seems to be quite dramatically improved fuel consumption.

Thanks to everyone for their help.