SL/R230: Transmission 'thunk'....maybe?
Thread Starter
Newbie
Joined: Aug 2003
Posts: 19
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From: London, England
Transmission 'thunk'....maybe?
When I slow to a stop and just as the car is at about 5mph, there is a distinct noise, a bit like a muted 'thunk', which seems to be coming from the rear axle area. This sound is heard and felt as well although it is really very slight.
Now although I can't be certain, it feels like transmission slack or 'driveline shunt' as the auto slips from 2nd to 1st on its way to a stop.
Took the MB mechanic out for a drive to demonstrate the problem and, guess what, the old denstist syndrome.....no 'thunk'.
All the guy could come up with is the surprising revelation that the elctronic brake system releases pressure automatically when the car stops to unload the suspension and prevent jerking, so no need for the driver to do this himself and maybe that was causing the problem. Dohhhhh.....
Can't get the breaking to do anything like this as the car will jerk if the driver keeps his foot hard on the pedal to a stop and, in any case, I don't think that this has anything to do with the 'thunk'.
Of course, as soon as I drove away from the dealership, it 'thunked' beautifully.
Any ideas?
Now although I can't be certain, it feels like transmission slack or 'driveline shunt' as the auto slips from 2nd to 1st on its way to a stop.
Took the MB mechanic out for a drive to demonstrate the problem and, guess what, the old denstist syndrome.....no 'thunk'.
All the guy could come up with is the surprising revelation that the elctronic brake system releases pressure automatically when the car stops to unload the suspension and prevent jerking, so no need for the driver to do this himself and maybe that was causing the problem. Dohhhhh.....
Can't get the breaking to do anything like this as the car will jerk if the driver keeps his foot hard on the pedal to a stop and, in any case, I don't think that this has anything to do with the 'thunk'.
Of course, as soon as I drove away from the dealership, it 'thunked' beautifully.
Any ideas?
Out Of Control!!
Joined: Jul 2002
Posts: 28,933
Likes: 12
Now that you mention your axle I do recall a service campaign going on with R230's talking about the axle. I suggest taking it in with your dealer and mentioning the campaign to him. I wish I had more information though.
MBWorld Fanatic!
Joined: Feb 2003
Posts: 5,856
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From: Sugar Land, Texas
09' 335i coupe
Re: Transmission 'thunk'....maybe?
Originally posted by oldrascal
When I slow to a stop and just as the car is at about 5mph, there is a distinct noise, a bit like a muted 'thunk', which seems to be coming from the rear axle area. This sound is heard and felt as well although it is really very slight.
Now although I can't be certain, it feels like transmission slack or 'driveline shunt' as the auto slips from 2nd to 1st on its way to a stop.
Took the MB mechanic out for a drive to demonstrate the problem and, guess what, the old denstist syndrome.....no 'thunk'.
All the guy could come up with is the surprising revelation that the elctronic brake system releases pressure automatically when the car stops to unload the suspension and prevent jerking, so no need for the driver to do this himself and maybe that was causing the problem. Dohhhhh.....
Can't get the breaking to do anything like this as the car will jerk if the driver keeps his foot hard on the pedal to a stop and, in any case, I don't think that this has anything to do with the 'thunk'.
Of course, as soon as I drove away from the dealership, it 'thunked' beautifully.
Any ideas?
When I slow to a stop and just as the car is at about 5mph, there is a distinct noise, a bit like a muted 'thunk', which seems to be coming from the rear axle area. This sound is heard and felt as well although it is really very slight.
Now although I can't be certain, it feels like transmission slack or 'driveline shunt' as the auto slips from 2nd to 1st on its way to a stop.
Took the MB mechanic out for a drive to demonstrate the problem and, guess what, the old denstist syndrome.....no 'thunk'.
All the guy could come up with is the surprising revelation that the elctronic brake system releases pressure automatically when the car stops to unload the suspension and prevent jerking, so no need for the driver to do this himself and maybe that was causing the problem. Dohhhhh.....
Can't get the breaking to do anything like this as the car will jerk if the driver keeps his foot hard on the pedal to a stop and, in any case, I don't think that this has anything to do with the 'thunk'.
Of course, as soon as I drove away from the dealership, it 'thunked' beautifully.
Any ideas?
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Junior Member
Joined: Jan 2003
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From: Europe
R230
Originally posted by vraa
Now that you mention your axle I do recall a service campaign going on with R230's talking about the axle. I suggest taking it in with your dealer and mentioning the campaign to him. I wish I had more information though.
Now that you mention your axle I do recall a service campaign going on with R230's talking about the axle. I suggest taking it in with your dealer and mentioning the campaign to him. I wish I had more information though.
please tell me some more details about this campaign, where can i find any info about it? I had some similar noises, at first the MB mechanic said it was something wrong with the transmission but later they only changed the transmission oil and told me that the factory used the wrong type of oil... strange isn't it?
Regards
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Thread Starter
Newbie
Joined: Aug 2003
Posts: 19
Likes: 0
From: London, England
Got it!
It turns out that the culprit is nothing to do with the transmission but is attributable to the fancy electronic braking system, specifically, a sticking rear caliper which.
And it also seems that the MB shops know all about this problem and have a set of procedures for remedying iy. Starting with bleeding the system and, if that doesn't work, more invasive work.
Hope this helps.
And it also seems that the MB shops know all about this problem and have a set of procedures for remedying iy. Starting with bleeding the system and, if that doesn't work, more invasive work.
Hope this helps.
