stevebez

Well been living with this for a while now (it may have been there all along) and its beggining to annoy me - actually something my wife noticed and brought to my attention and increasingly now its been annoying me ..........

I get on the gas WOT, for maybe 2-3 seconds (want to keep my licence thanks), and as I back off the throttle the car slows and then lurches again quite abrubtly... Maybe I got the order wrong (i.e. maybe lurches and then slows abruptly) but its really uncomfortable... I initially thought it was the S/C engaging / disengaging or something but it feels more dramatic than that...

Almost feels the tranny is still wound up and cannot get rid of the inertia as you come off the throttle and then its released into a lurch... If I come off the throttle gently the lurch is not there - only if I go from WOT to off the gas completely, do I get this "buck".

Most noticible in the low gears... trying to understand whats going on here and whats up mbe the tuning, mbe the gearbox ecu, mbe the s/c clutch - a little bit lost here at mom....

Any thots?

Havoc

I recently felt the same jerking on my car which was noticeable in the low gears when I would let off the throttle. The throttle felt off at times as well. I don't have the right tune so that could be the problem. The trans felt like it was shifting harder and the jerking would happen right after a down shift, so I can understand how one would think it's the gearbox tcu. Vadim just installed the upgraded SC clutch so maybe the pulley is the cause. I'll let you know if it goes away once Vadim gets it tuned right. My guess would be when the SC goes from boost to no boost durning a down shift something is not reading right.

Zod

this was mentioned b4 in an other thread.

My Symptoms were as follows:

Accelerating in lower gear and while the revs are going up i let off the gas, but then the car gives me a thud ''buck'' effect.
i assume its changing gears expecting the revs to keep coming, but then they stop as its shifting causing this effect.

The cure is as follows.......brake earlier to not make it up shift and you will not get the thud. thud does not happen if the speed is consistent with shifts.
Basically i have a feel for it now and know when its going to happen, so i can stop it.

some people have mentioned to change the engine mounts, have done but it has come back
hope this helps, you can try it out your self

be in lower gear ''auto'' accelerate then off the throttle as its about to change, you get the thud

Yacht Master

I have had this happen once, the neck snapping jolt/buck is more than uncomfortable. I think it is the torque converter locking up or software overruns and makes sloppy shift. What ever is going on it is not good. I try to avoid any quick lift now.

stevebez

Yep you basically need to lift off slowly cannot got 100% to zero - otherwise you get the "buck"...

Would be nice if there was a ECU / TCU / tranny software upgrade to overcome this...

stevebez

It might have something to do with the bypass valve opening up while the S/C is still pumping hard, the sudden release of the S/C load will jerk the car fwd... ?? Mbe mistiming of the S/C clutch and bypass valve...dunno still need to work this one out.

It was much less notible when car was stock if I remember correctly? Anyone still stock? with the same experience?

DFW01E55

Anyone?
It's unmistakeable when you get out of the gas quickly, you might think something broke.

stevebez

I think its the torque convertor going from locked to unlocked to slowly... So coming off the gas fast does not give the TQC time to release and let the car roll.

stevebez

And on an aside just noticed 997TT 2nd hand prices dropped around 10% over last month here - just collapsed.

08 with 1k miles can be had for £89k, was £110 new. Ouch.

jangy

about 40K miles?

stevebez

?

1k miles... mbe it has a fresh coat of paint somewhere ...

DFW01E55

Truly horrific pricing in the UK.
This might make you sick.

ChicagoX

Steve,

From what I read, the tranny will deliberately hold a gear if you lift off suddenly, as it thinks you came up on slower traffic and need to use engine braking.

More boost + bigger TB seems to exacerbate the issue for whatever reason according to anecdotal forum info.

I Like Soup

Mine does the bucking thing to but it does it when I'm hard on the throttle and then lift abruptly...I thought it was pretty obvious why it was doing it, but then again, I just assumed it was the increased horsepower from the new pulley/tune and stuff.

rpmnospin

I'm stock (in the stix of Tennessee) and the same thing happens to me every once and a while. I usually get it when I have to mash the gas on the highway to pass some bozo who is in the left "fast" lane going 55 and then let up quickly when the goof ball moves over to the right lane and cuts me off at the last possible second. I get that very hard "buck". Like -- did someone just crash into the back of me and my mind has not caught up with the event yet? I too have learned to try hard to moderate how fast I let up off the gas -- of course, most of the time I have no choice. It sure is embarassing when someone else (like my wife and 7 year old child) is in the car. Oh well --

supre55

Same deal for me as well... car holds gear longer and then after abrupt throttle letoff north of 5500 rpm it "bucks". I have always attributed to the delta between full blown acceleration and high rpm engine braking.

Peter_02AMG

I have the same problem with my Kleemann S/C from day one. I always thought that the torque and forward momentum pin you to the seat and as you let off the gas abrupt the weight of the car decelerate like hitting the brake and the people included stuff inside the car kept on moving forward. I see that jurking forward movement in my passenger after a hard acceleration all the time. I didn't know if that was normal

Hammer Down

It's the German Horses under the hood saying WTF! why did you let off

rarfinancial

Well I have a CLS 63 and I get the same type of bucking I think it has something to do with ESP. Try turning off ESP and see if it still happens.

Murtaza

Going home from work in 20min, going to try with ESP on and off to see what happens. I haven't had my 55 for that long and I haven't noticed any bucking, I usually don't let off when going WOT; usually shift up and then let off...

Zod

If you let off before the shift, thats when it happens

Murtaza

Just tried it a bunch of times, in M an S modes, went WOT till about 6k and let off, no jerk... ESP was on.

I Like Soup

This obviously isn't a problem with those underpowered '63's...

Zod

its on lower gear i.e 1rst going on to 2nd, or 2nd going on to 3rd (not 100% sure) going fast then letting off fast before the shift. If you do not get it be happy , do not really know why you are trying to get the effect

ps. this is in auto mode, is more noticble in C mode, but happens in S mode also, at rpm's lower then 6k...3-5k rpms i think

Murtaza

I did them in 2nd and 3rd gear, went WOT to 6k and let off in M and S...will try C tommorow along with 1st gear runs. Not trying to get the effect, just want to see if I have the same problem