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Auto downshift while braking

 
Old 07-24-2013, 08:11 AM
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2012 ML350 BT
Auto downshift while braking

I have mixed feelings on this - What do y'all think...?

While braking, particularly under 25 mph, my 2012 ML350 will noticeably downshift. You'll actually see the RPMs jump and feel the transmission "assist" in slowing the vehicle.

On the upside, I suppose this may reduce brake wear. It also gives me the torque I expect to accelerate.

On the downside, it's harder to brake to a stop smoothly. I don't mind it so much myself, but can be embarrassing with passengers. As the gears grab, I instinctively let up slightly on the brakes (around 20 mph) but then end up braking harder to stop (false confidence, I suppose).

It's not a huge deal and I only recently figured out what was happening. Maybe I'm still used to my old Rover HSE.


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Old 07-24-2013, 02:41 PM
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Engine braking assists in stopping the vehicle and keeps the vehicle at optimum engine speed for acceleration. If you were manually shifting a car or motorcycle, you'd match shifts under braking, so wouldn't you imagine an automatic will do the same thing?
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Old 07-24-2013, 03:11 PM
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Originally Posted by jesterdfw
Engine braking assists in stopping the vehicle and keeps the vehicle at optimum engine speed for acceleration. If you were manually shifting a car or motorcycle, you'd match shifts under braking, so wouldn't you imagine an automatic will do the same thing?
Sure, I get that. I've just never noticed it (let alone to be so pronounced) in any other car I've driven.


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Old 07-24-2013, 04:24 PM
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2013 ML350 Bluetec
I have the same issue in my 2013 ML350 Blutec. In fact, with AC runing downshifting is more jerky and it is almost impossible to smoothly decelrate to 0. I really do not like the brake feel with the transmission downshifting with the speed decreasing to 0. Thats pretty much the only gripe I have for this vehicle!
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Old 07-25-2013, 12:42 AM
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How many all-time-four-wheel-drive vehicles have you owned before ?

Different feel, you will be surpised if you open minded on adjusting driver patterns..
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Old 07-25-2013, 08:19 AM
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I don't think it has anything to do with the fact that it is a 4-wheel drive. But if it does, then MB needs to fix it. I have owned other 4-wheel drive vehicles (Lexus, RangeRover) and this is not typical behavior.
In the ML, the initial brake input feels spongy until you depress the pedal a little more when the brakes grab quickly and that's when you start overcontroling the brake inputs. I have tried another ML2012 and it is pretty much the same thing. I would say, the ML electric brake system need tweeking at low speed.
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Old 07-25-2013, 09:36 AM
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Try complaining about it the next time the car is at the dealer.

About six months ago, I complained about abrupt downshifts while coming to a stop, along with stumbling while the engine was cold. (I exaggerated the severity of both because MB dealers won't check for software updates routinely. There has to be a a specific customer complaint, or official recall.)

They did find a software update for the transmission control unit that seemed to help somewhat. I don't know whether the update was designed to address these particular problems, though.
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Old 07-26-2013, 01:22 PM
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Originally Posted by Shrdlu
Try complaining about it the next time the car is at the dealer.

About six months ago, I complained about abrupt downshifts while coming to a stop, along with stumbling while the engine was cold. (I exaggerated the severity of both because MB dealers won't check for software updates routinely. There has to be a a specific customer complaint, or official recall.)

They did find a software update for the transmission control unit that seemed to help somewhat. I don't know whether the update was designed to address these particular problems, though.
Same here on both issues. I really did (and still do) feel that something isn't right. Of course, the dealership said that everything seemed normal.


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Old 01-28-2014, 02:32 PM
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2013 ML350
Abrupt Downshift

Same exact issue, seems to happen at when slowing down and at 20 mph. It is quite abrupt. My dealership wasn't able to find any software update that corrected it. Had it in 2 times and they said they see no error messages and couldn't recreate it themselves. It seems to have started at around 14,000 miles and I agree it's more significant with the A/C on. Since it has been colder here in Florida and I haven't had the A/C on when I first start the car, it doesn't seem to be doing the downshift. It will be interesting to see if it starts up again when it's really warm out. So frustrating though that they aren't able to see any message that something is wrong.
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Old 01-29-2014, 04:19 AM
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ML350 BT soon......pleeeease. GOT IT NOW....Wooooo
Originally Posted by Semibru View Post
I have mixed feelings on this - What do y'all think...?

While braking, particularly under 25 mph, my 2012 ML350 will noticeably downshift. You'll actually see the RPMs jump and feel the transmission "assist" in slowing the vehicle.

On the upside, I suppose this may reduce brake wear. It also gives me the torque I expect to accelerate.

On the downside, it's harder to brake to a stop smoothly. I don't mind it so much myself, but can be embarrassing with passengers. As the gears grab, I instinctively let up slightly on the brakes (around 20 mph) but then end up braking harder to stop (false confidence, I suppose).

It's not a huge deal and I only recently figured out what was happening. Maybe I'm still used to my old Rover HSE.


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mine is smooth' noticeable,but smooth and no problem for controlled braking....see your tech.

mlee
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