Shifting Delayed w/Engine is Hot
08-10-2012, 03:59 PM
#27
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That's what I thought too Bud, but low and behold, it happened. Think it's possible that the rpm speedup is a leftover software issue? Should mention that I have a 207 Cab. Possible difference there as well.
Last edited by mambrose23; 08-10-2012 at 04:02 PM.
09-27-2012, 02:29 PM
#28
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2011 E550, 2013 GLK
Engineering has responded about this issue. It is considered normal and there is a reason for it.
It's something that has trickled down from AMG into regular V8's and is a method to cool the transmission.
When the transmission reaches a certain temperature and the A/C is running, the transmission is shifted to a lower gear to increase engine RPM. I thought it was to help engine cooling but it turns out it's to help transmission cooling.
It's tied to the A/C so when I turned it off, I was then allowed to force an up shift.
From now on I am not going to try to override the system by turning off the A/C.
It's cooling off here in Arizona now so I'm not experiencing the situation.
It's something that has trickled down from AMG into regular V8's and is a method to cool the transmission.
When the transmission reaches a certain temperature and the A/C is running, the transmission is shifted to a lower gear to increase engine RPM. I thought it was to help engine cooling but it turns out it's to help transmission cooling.
It's tied to the A/C so when I turned it off, I was then allowed to force an up shift.
From now on I am not going to try to override the system by turning off the A/C.
It's cooling off here in Arizona now so I'm not experiencing the situation.
08-25-2013, 08:17 PM
#32
Member
Phew, am I relieved to see this thread. I've been seeing the same behavior of delayed shifts, I'd narrowed it down to hot days when starting after the car had not fully cooled. Being in Houston the AC is always on, I'm going to try cycling it off tomorrow to see if that "fixes" things.
Car in question is a 2010 E550, no other transmission issues.
FYI my commute is through neighborhoods and I don't go over 45 mph; in the morning with a cold car and outside temp in the 80's I see the normal half mile of delayed shifts (catalytic converter warm up) followed by normal transmission behavior. Which means when burbling along I'm in top gear at around 1000 rpm.
If I use the car for lunch or something so it is hot when I come to drive home in the evening outside temp up to 100 F, then it will hold onto gears to a little over 2000 rpm which means I never get out of 4th on the way home. If I drive far enough the transmission will eventually sort itself out and without any input from me switch up from 4th to top; after that it's fine.
Will report back with details of whether the AC trick clears things.
Big thanks for discussing this issue.
Peter
Car in question is a 2010 E550, no other transmission issues.
FYI my commute is through neighborhoods and I don't go over 45 mph; in the morning with a cold car and outside temp in the 80's I see the normal half mile of delayed shifts (catalytic converter warm up) followed by normal transmission behavior. Which means when burbling along I'm in top gear at around 1000 rpm.
If I use the car for lunch or something so it is hot when I come to drive home in the evening outside temp up to 100 F, then it will hold onto gears to a little over 2000 rpm which means I never get out of 4th on the way home. If I drive far enough the transmission will eventually sort itself out and without any input from me switch up from 4th to top; after that it's fine.
Will report back with details of whether the AC trick clears things.
Big thanks for discussing this issue.
Peter
08-25-2013, 09:59 PM
#33
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08-25-2013, 10:47 PM
#34
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Good point, thank you, I really want to test out the AC operation as I'll feel a lot better if I'm sure it's not a transmission issue.
Are others seeing what I see in that the holding onto low gears only happens for a few miles (guess it depends how hot it is outside) after starting hot. Once my transmission has started to behave normally it never reverts to holding onto gears; maybe I haven't driven it far enough on a hot enough day. Would love to hear from those who have seen this issue. Also is it only 550's that do this?
I'm no expert on MB cooling/automatic transmissions but am a little suspicious of the explanation and even more so if MB's logic for cooling the transmission can be defeated by turning the AC off and on.
Peter
Are others seeing what I see in that the holding onto low gears only happens for a few miles (guess it depends how hot it is outside) after starting hot. Once my transmission has started to behave normally it never reverts to holding onto gears; maybe I haven't driven it far enough on a hot enough day. Would love to hear from those who have seen this issue. Also is it only 550's that do this?
I'm no expert on MB cooling/automatic transmissions but am a little suspicious of the explanation and even more so if MB's logic for cooling the transmission can be defeated by turning the AC off and on.
Peter
Last edited by T100T; 08-25-2013 at 10:54 PM.
07-26-2021, 09:42 PM
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MB E550
E550 won't upshift on hot days
My 2014 E550 has a similar problem, when the outside temp is above 30c/87f it won't upshift past D4 in city driving. In cooler weather it shifts up to D6 on the same streets at the same speed.
I haven't tried the A/C trick but will on the next hot day
Sometimes it will upshift if I quickly accelerate for a 'few' feet (not recommended in heavily patrolled areas.
)
And at highway speeds it's normal
Cheers
I haven't tried the A/C trick but will on the next hot day
Sometimes it will upshift if I quickly accelerate for a 'few' feet (not recommended in heavily patrolled areas.
)And at highway speeds it's normal
Cheers
I have a 2011 E550 (3/2011 build date). Recently, I've experienced a problem where the the transmission won't shift into 7th gear when the engine is hot.
The symptoms are similar to the delayed shift when the engine is cold. Mercedes delay the shift to heat up the catalytic converter. This only lasts for a few minutes at the most and is normal.
My problem is that this occurs when the engine is hot and won't shift up even after driving several miles at 50 MPH. I don't know if this is a problem with very hot weather since I live in Arizona.
If I take the car out with the engine cold, drive it until the engine is warm, park the car for some minutes and then restart the car and continue driving, it won't shift into 7th gear.
Now here is something interesting and works every time. If when I'm driving, I turn the A/C compressor off for a few seconds and then turn it back on it will shift into 7th and act normally from then on.
All of these symptoms are pretty consistent since the weather got hot. The problem didn't occur last year.
I recently had the car in for service and there were no outstanding Service Bulletins for my VIN number. I didn't mention this problem at that time.
Has anyone had a similar experience or have an idea about what could be wrong? It's as if there is a bad sensor somewhere.
The symptoms are similar to the delayed shift when the engine is cold. Mercedes delay the shift to heat up the catalytic converter. This only lasts for a few minutes at the most and is normal.
My problem is that this occurs when the engine is hot and won't shift up even after driving several miles at 50 MPH. I don't know if this is a problem with very hot weather since I live in Arizona.
If I take the car out with the engine cold, drive it until the engine is warm, park the car for some minutes and then restart the car and continue driving, it won't shift into 7th gear.
Now here is something interesting and works every time. If when I'm driving, I turn the A/C compressor off for a few seconds and then turn it back on it will shift into 7th and act normally from then on.
All of these symptoms are pretty consistent since the weather got hot. The problem didn't occur last year.
I recently had the car in for service and there were no outstanding Service Bulletins for my VIN number. I didn't mention this problem at that time.
Has anyone had a similar experience or have an idea about what could be wrong? It's as if there is a bad sensor somewhere.
07-26-2021, 10:12 PM
#36
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'11 E350, '11 E550, '98 M3, '95 E320
Seems like an odd issue as described... with the A/C on and "high" ambients, I wouldn't expect the car to shift into a high gear and lug the engine. City driving, what are we talking 40-50 mph?
Rough napkin math: 1500rpm, 6th gear (0.82), 2.42 diff, 25.7 in wheel diameter ~ 60 mph. So 40-50 mph is 1000-1300 RPM, I could see around 1300. Driving the E350 it will stay around 1300-1500 in the 40-ish mph range in moderate A/C weather (in 70-80*s) when driving steady. The E550 on the other hand, I haven't paid much attention in that regard.
Does is matter if your in transmission mode E or S?
Rough napkin math: 1500rpm, 6th gear (0.82), 2.42 diff, 25.7 in wheel diameter ~ 60 mph. So 40-50 mph is 1000-1300 RPM, I could see around 1300. Driving the E350 it will stay around 1300-1500 in the 40-ish mph range in moderate A/C weather (in 70-80*s) when driving steady. The E550 on the other hand, I haven't paid much attention in that regard.
Does is matter if your in transmission mode E or S?
07-27-2021, 12:40 PM
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MB E550
E550 delayed upshifting
Looks like BudC answered this - see post #28.
Annoying but there it is. Let's hope the heatwave is coming to an end.
Funny, MB supported Rommel during the African campaign of WWII - I'd wager these vehicles didn't have shifting problems.
Then again they probably didn't have A/C or auto trans
Thanks Bud
Annoying but there it is. Let's hope the heatwave is coming to an end.
Funny, MB supported Rommel during the African campaign of WWII - I'd wager these vehicles didn't have shifting problems.
Then again they probably didn't have A/C or auto trans
Thanks Bud
