reverse clunk

[scruffy]

when selecting reverse from cold my 209 auto engages with a loud clunk, doesn't happen all the time or with forward gear selection and not at all when hot.

Does anyone else's car do the same or is it something to investigate further.
Car is garaged overnight.

S

 

[liammc]

My SL280 does the same same thing. I have to hold the car quite firmly with the brake when selecting drive or reverse. Dont know if its a bad sign or not.

 

[Brian WH]

I would try and change the Gearbox and Torque Convertor oil and see if that improves it mate. The oil level could be low anyway and not engaging properly.

 

[andy_k]

points to consider before you start taking the cars to pieces


1, don't your boxes have a "hard shift" designed to help get the gearbox and engine up to temperature quicker?

2, when the engine is cold it will tick over slightly quicker which will also make the changes (particularly into reverse) a little harsher

3, when the engine has just been started oil has not fully circulated around the transmission and it's not up to full pressure - a slight clunk is to be expected

to me it sounds like pretty normal behaviour for an automatic transmission

Andy

 

[scruffy]

Hi andy

I kind of assumed its oil related, its only just had a dealer service so assume the levels are ok (or can you).

Not heard of a hard shift though, any more info.

I'll keep an eye on it as the weather gets colder, spose I could reverse in at night and avoid the issue completely, but thats being ridiculous isn't it!

S

 

[andy_k]

most MBs will have a device on the gearbox that forces the gearshift to be a little harsher when everything is cold - this is to force the car up to operating temperature quicker.

From the sound of it all you are experiencing is a cold transmission with oil that's not fully warmed not engaging as smoothly as it does when it's hot, just that it's more pronounced in reverse as the gear ratio is higher

Andy

 

[Brian WH]

most MBs will have a device on the gearbox that forces the gearshift to be a little harsher when everything is cold - this is to force the car up to operating temperature quicker.

From the sound of it all you are experiencing is a cold transmission with oil that's not fully warmed not engaging as smoothly as it does when it's hot, just that it's more pronounced in reverse as the gear ratio is higher

Andy

I agree with your methodology, but cannot agree that "a slight clunk is to be expected". In my opinion the "clunk" should be negligible, and undetectible.

I am still of the opinion that the oil is low or old.

 

[mark.t]

clunk

is your car parked on a slight incline even enough for it to roll in neutral if so when you come to a halt in your garage your foot brake will still be on then you engage park this will hold on the incline ...but the car will roll slightly then when you start in the morning and select reverse it will clunk because of the slight roll forward which happened the last time you parked it :bannana:

 

[scruffy]

Good point, the car is parked on a flat surface however will reverse a touch before switching off to give it some slack to see if that cures it.

Tend to agree with brian that any clunk should be negligable, MB are supposed to make the best auto gbox's aren't they.

Will speak to the dealer also re oil levels, sure its nothing but just homing on any possible probs before my warranties up next year.

 

[mark.t]

Good point, the car is parked on a flat surface however will reverse a touch before switching off to give it some slack to see if that cures it.

Tend to agree with brian that any clunk should be negligable, MB are supposed to make the best auto gbox's aren't they.

Will speak to the dealer also re oil levels, sure its nothing but just homing on any possible probs before my warranties up next year.

my drive is flat so i just drive in stop on foot brake slip the the car into..N..then after that release footbrake car is stiil then slip into ...P...mine has clunked on incline or when ive stopped quickly and just put it in park...