mpwnbr
Senior Member
- Joined
- Sep 28, 2014
- Messages
- 81
- Reaction score
- 0
- Location
- Liverpool, UK
- Your Mercedes
- Mercedes CL600 / 2007 / 5.5 litre
A few weeks back my car decided to stop driving; their was power available but there was some sort of lock on the transmission or gears. Anyway, after loading it onto a flatbed truck, Mercedes repaired the car by fitting a new Transmission Control unit to the gearbox. All sorted I hoped. However since that repair the drive of the car has been so different, with the symptoms being a few fold.
Firstly there appears to be some sort of resistance to the drive. It's difficult to explain, but if I accelerate to a certain speed, lets say 40mph, and then take my foot off the gas, the car decelerates at an unusually quick rate. It's like there's something that's stopping the car from free wheeling properly. This is best demonstrated by driving down a hill, which I do and continually test on my daily commute, and when I take my foot off the accelerator, the car actually decreases in speed. Unfortunately CL600's didn't exist in Newton's days, and maybe his theories may have been a little different had they been around, but everyone of us knows that if you do freewheel down a hill then the speed will increase. Not mine!
Another symptom is the gear change of the car, which is certainly less smooth than previously, in fact quite jerky, and is then followed with higher revs than I seem to recall prior to the new Transmission Control Unit.
And finally, there's also another noise coming from the car, which can be noticed when driving along a quiet road with windows open. As speed increases the noise gets quicker and as speed decreases the noise gets slower. Imagine if you had a sticker on the surface of a new tyre; it's that sort of rotational/rubbing/friction noise. I've taken a look for a few possible issues such as warped brake disc with pad rubbing on it, but all discs seem to be the same temperature after a drive. I've also looked at the inner face of the tyres in case there's any delamination or other damage that could be providing this noise, but again there's no sign of a problem.
So this all brings me back to the Transmission Control Unit, and although I returned my car back to Mercedes earlier this week, they test drove it and put it on the Star Machine, they weren't able to pick up any errors or identify any problems.
So, as ever you guys are a wealth of knowledge and good ideas, so I was hoping for some more assistance.
Any ideas would be more than welcome.
Thanks,
Mark
Firstly there appears to be some sort of resistance to the drive. It's difficult to explain, but if I accelerate to a certain speed, lets say 40mph, and then take my foot off the gas, the car decelerates at an unusually quick rate. It's like there's something that's stopping the car from free wheeling properly. This is best demonstrated by driving down a hill, which I do and continually test on my daily commute, and when I take my foot off the accelerator, the car actually decreases in speed. Unfortunately CL600's didn't exist in Newton's days, and maybe his theories may have been a little different had they been around, but everyone of us knows that if you do freewheel down a hill then the speed will increase. Not mine!
Another symptom is the gear change of the car, which is certainly less smooth than previously, in fact quite jerky, and is then followed with higher revs than I seem to recall prior to the new Transmission Control Unit.
And finally, there's also another noise coming from the car, which can be noticed when driving along a quiet road with windows open. As speed increases the noise gets quicker and as speed decreases the noise gets slower. Imagine if you had a sticker on the surface of a new tyre; it's that sort of rotational/rubbing/friction noise. I've taken a look for a few possible issues such as warped brake disc with pad rubbing on it, but all discs seem to be the same temperature after a drive. I've also looked at the inner face of the tyres in case there's any delamination or other damage that could be providing this noise, but again there's no sign of a problem.
So this all brings me back to the Transmission Control Unit, and although I returned my car back to Mercedes earlier this week, they test drove it and put it on the Star Machine, they weren't able to pick up any errors or identify any problems.
So, as ever you guys are a wealth of knowledge and good ideas, so I was hoping for some more assistance.
Any ideas would be more than welcome.
Thanks,
Mark
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