Odd gearbox behaviour - SL500

rexemper

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Hi

Just back from a quick run out in the SL - needed to go to the shops. Normally the 7G gearbox is lovely and smooth and you don't really notice the box changing up and down.

However, twice now it has exhibited some strange behaviour. On these occasions, it has taken a lot more revs to get it moving and it fails to change up normally. The first time this happened, I was redlining it on the rev counter and it was only doing about 40mph and it wouldn't change up.

It did the same sort of thing again today and I also noticed that when I put it in reverse it wouldn't really move even though I was revving it. Changing it back to Drive and there was a loud 'thunk' and then it would move. I changed it from D to P a few times and there was a loud thunk each time (my BMW has always down this when changing from P to D).

Each time this has happened, switching the car off and then on again seems to restore things to normal. On the two times it has done this, it has been from when I turn the car on as opposed to starting to happen whilst driving.

Its very odd as the gear indicator was showing D and S in the display which is what its normally on.

Any ideas or thoughts???
 

Craiglxviii

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I'd start with a transmission fluid change, it can't hurt and in many of these cases cures the problem.
 

star

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Get the fault read BEFORE doing an oil change, it sounds like the tcu is going down, so the oil will be changed when doing the tcu.
 
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rexemper

rexemper

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Get the fault read BEFORE doing an oil change, it sounds like the tcu is going down, so the oil will be changed when doing the tcu.

Thanks. Is that an expensive fix?? Will I need to get it onto a STAR machine to get the fault read?

According to the service book, the transmission oil was changed about 5k miles ago.
 
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rexemper

rexemper

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Willing be taking the SL into Star in Reading tomorrow as I never got round to getting this seen to. A change of battery earlier in the year seemed to make the problem go away but it's definitely doing it again (the battery change was probably unrelated anyway!).

Fingers crossed it isn't too expensive a fix...
 

bembo449

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let us know what the diagnosis is and then the fix for it pal , ive been planning a fluid change on the 216
 
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rexemper

rexemper

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Update - been to see the chaps at Star. Not the best news - needs a new valve body as the cheaper repair option isn't possible...

This will be north of £1300 so quite a bit more than just a fluid change!

On the upside, the chaps at Star were very helpful and friendly and even showed me the parts in question from another car.

Bugger! Deep breath.
 

flowrider

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Update - been to see the chaps at Star. Not the best news - needs a new valve body as the cheaper repair option isn't possible...

This will be north of £1300 so quite a bit more than just a fluid change!

On the upside, the chaps at Star were very helpful and friendly and even showed me the parts in question from another car.

Bugger! Deep breath.
Not great news but not terrible either. At least you now know what the issue is.
 
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rexemper

rexemper

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Not great news but not terrible either. At least you now know what the issue is.

Yes, you're right. I guess I was hoping I'd be able to have the guild changed and be done. Oh well, the first big bill of SL ownership strikes!
 

bembo449

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its one thing that always looms over those of us with luxury vehicles pal , like the AMP on my 216 at £1100 ! gulp
 

John Laidlaw

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I agree, could be a lot worse....at least you know it's getting done right too!
 

kid-jensen

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Presumably the fluid change 5K miles ago was before you bought it?

If so, I guess you've just found out why the PO sold it...
 

craigdm

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They had my 60k mile CLK for 3 weeks when this happened to me about 4 years ago. The £1300 bill drove me away from the brand until I came back a couple of months ago.

The delay was due to there being no reconditioned parts being available in the UK. Eventually, after many emails and phone calls to head office they agreed to fit a new part for the same price as a recon part.

See here :

http://forums.mercedesclub.org.uk/index.php?threads/7g-box-full-of-neutrals.129131/
 

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