SL Gearbox Update - Major Problem

[db1]

Hi,

My SL55 was diagnosed with a faulty control and this has now been upgraded.

The Upgrades were (as per the note from dealer):

27-4982-01 2hrs Electrohydraulic control unit for automatic transmission. Remove and replace as required for veh with transmission 722.6

27-2351-01 0.3hrs Control unit. Replace Vehicle with transmission 722.5/722.6 (following testing)
27-1046-01 0.5hrs Adaptation Perform Veh with transmission 722.6 MBNA


I noticed a few changes:

1. The display modes for the gearbox are C, S, M - and not W, S, M anymore.
2. You can now use the steering wheel gear changes whilst in D mode.

However there is a new really worrying symptom which is very harsh downshifts. I was told that it takes some time for the new control unit to "learn" the new driving characteristics etc and to expect around 200 miles or so before this settles.

The downshifts are particularly harsh from 4 - 3 when accelerating medium hard. Also, when on overrun (ie foot not on gas) and then coming back on the gas also causes a large jerk as the gearbox engages and downshifts.

I have so far done about 100 miles since collecting the car. Of course, I can't imagine that these jerks etc do the drivetrain any good so the quicker this thing "learns" the better.

My question are:

Is this normal?
How long should I expect this to go on?
What are the new gearbox modes C, S as compared to what there was before.


Any advice welcomed on this....

update: driving again this w/e was horrible. car back to dealer on monday...with an annoyed owner on the end of the phone.

 

[saorbust]

C - Comfort
S - Sport
M - Manual.

W used to be Winter I believe, effectively the same as C, but people didn't run in engines in Winter mode so they changed it. Now the manual says (you did read it right ? to run in for 1,000 to 1,500 miles in C mode. It did in my CLK anyway).

C effectively means smoother shifts (ie, not so agressive, lower RPM, more time between changes). It also means start in 2nd gear - so it can be used as a Winter mode.

As for being normal, doesn't sound like it. I only ever had that once - turned out to be a misfire. I think you are right to take it back. Having said that they obviously had a fault to rectify in the first place.

I have known a learning transmission to take over 500 miles. Its easy to spot, the car sometimes (not all the times) appears to be jerky in its changes, and occasionally doesn't find the right gear. By default the setting is set to the least responsive, and then you make the gear changes, acceleration pedal more responsive by 'requesting' - its all electrical nowadays - more power more early.

Clarky.