athanasy

Hi there:

I really need your experties here...

Just got my new c450 for couple of months and now there's about 2K KM on it. I'm a believer of "breaking in period" and I have been very careful with the first 2K, never stepped on GAS too hard and never used sports or sports plus mode.

I switched on the sports plus mode for the first time yesterday since it's already passed 2K. When I pulled ahead at a red light (stepped on gas really hard, about 6000-7000 RPM) then let go of the gas, the car basicly jerked really bad and noticeably 4 time in a roll, and every time it jerked RPM dropped about 1000. I have tested it again and same thing happened another time. I understand when you let go of gas the computer is trying to gear up but it felt horrible.

I'm little scared right now, although everything feels normal in other modes and gear shifting does feel fine still, is this kind of jerking in sports plus mode normal?

Thank you guys.

arnold0523

i test drove a C450 the other day. Transmission jerks at SPORT+. Sorry, couldn't help. but that's happening on that car I drove. It had 40 miles.

vic viper

Shifts are supposed to be harder in S+ nothing is wrong.

Zorq

I actually have the opposite, my tranny is not smooth in comfort. There was warranty work done on it to replace the "valve body" and reset the adaptation. Since then the car has been much better but it still not 100% smooth. From my understanding, this has something to do with how the tuning was done by AMG on our 7G Tronic.


Regardless, in your scenario, I'd recommend putting it in S+ and Manual, and do the exact same thing, step on it hard and let go of throttle, see if it's still dropping the RPM by 1000, it shouldn't in this case as your essentially holding the gear. If it still does, then you should bring it up with your dealership. In your case it could be that the timing of your de-throttle was matched with the computer's timing for shifting up so it created a bigger jerk than usual.


As with what most others have said, S+ does shift harder, and you don't really need it in city driving imho.


I think the most comfortable shifting behavior for our AMG tuned tranny is actually Sport mode. I prefer the shifting range of the Comfort though. The comfort does try to slow down shift speed considerably to the point that the car jerks the opposite way if you know what I'm trying to say. I'm hoping all these will be fixed later on as the C450 gets new firmware for the tranny. Hope this helps, cheers!

PeterUbers

I think you reset the tcu and drive exclusively in sport mode and in 500 miles problem will be gone

Terminator1

I have C250 and 16K KM on it. I also noticed that tranny is not always smooth. It can stay long for no reason in a specific gear @ high RPM, no matter which mode we talk about, while I expect it normally to shift up. Sport+ mode shifts gears somehow aggressively @6200 RPM with a bit of a delay. Like the tranny stays @6200 for a second and then shifts aggressively up with a noticeable yank. I also noticed several times when I floor it, the tranny downshifts to 6000 - 6200 RPM, stays there for a second and then shifts aggressively up. I cannot explain this behavior, because there is no logic in downshifting to ~6000 RPM (which is near the red line limiter). Because of that, I'm using regular Sport mode (which is smooth - any other mode is smooth), and manual shifting when in Sport+ mode to avoid yanks (shift just before the red line).

schvamf

My C450 does it as well in S+ mode, I assume it's normal as other cars I've driven do this as well when in similar modes. I prefer sport mode as others seem to.

Mr. J

When we test drove these cars in sport+ mode the throttle was very responsive on pressing it and just as responsive on the let off. If you come off the gas pedal with a jerking motion in sport+ you will feel it and the car will jerk, especially in low gear. This is not a defect of the vehicle.

This is a very similar feeling to coming off the throttle to quickly while in first gear with a manual transmission. The principal is the same, engine compression in low gear exerts more braking force upon the vehicle.

My wife and I both adapted to this instinctively. Both of us had learned on and had driven manual transmissions for years, so that throttle control is kinda hard-wired in I guess.

The fix, go smoother with the gas or switch from sport+ to sport or comfort mode.

Mr. J

This is incorrect^^^

A sport tuned transmission would still jerk in this scenario precisely because you are holding it in 1st or 2nd gear and coming all the way off the throttle.

In a typical automatic transmission (for example my dog car/grocery getter Ford Escape) if you stomp on the gas the car revs up and quickly accelerates. If you come off the gas rapidly the car will still jerk a little but the vehicle will almost always have shifted into a higher gear as you come off the throttle. The higher gear reduces the amount of mechanical advantage of the engine braking force applied so the severity of the lurching/jerkiness is much less.

The C450 and similar type vehicles with sport tuned transmissions are designed to hold the gear upon acceleration and bounce off of redline or close to redline for the shift points. So if you are pulling of the throttle rapidly you are going to to be in a lower gear than you would be in a typical car or in the comfort mode of the C450.

Maritime

Whatever, Portlandia, I love my c450.

Mr. J

que amigo?

Maritime

Regardless of your opinions on why or how it works, I love it.

matoo

How do you reset the tcu, i need to do this lol

imj0257

Useful info. Thanks.