so i went to put my car in reverse (car was cold) and i barely put my foot on the gas and the car reved up to around 3k rpms. had the car for around a month now it has 50k on the dot, from what carfax says the transmission was serviced at around 10k miles ago. i just recently had another instance where i was slowing down at a stop light and the light turned green so i eased into the gas and the rpms shot up aswell for a split second (these were the only two times its hiccupped like this). and also something else has been going on aswell at times when im cruising or just barely putting preasure on the gas to speed up a bit the car will instantly cut power it feels exactly like how it would feel losing traction but the traction light isnt coming on whatsoever when it happens.

the car is tuned and has a ecu software update recall from what the dealer has told me. has pure 1000 turbos, ecu tune, and im almost positive the TCU is tuned aswell.

Might be normal if I am reading it correctly, need forum member superswiss to chime in. See if this is related? https://mbworld.org/forums/c63-c63s-...ml#post9122123

Sounds like it might be normal based on your description of when it happens. Does it slip between any gear changes when you're accelerating with intention?

Sorry for the confusion. The post belongs to forum member superswiss, you need to ask him directly or ask in that thread linked.

Doesn't sound normal to be honest. On that other thread I was mainly commenting on the inherent slip that a clutch has, but revs shouldn't shoot up to 3k rpm during a gear change and such or cut power as you experience. When shifting hard under WOT, then the transmission pretty much shouldn't slip at all. It should slam the next gear in and you should not experience an interruption in power delivery. Maneuvering around slowly and during comfort shifts there will be some slippage to make things smooth, but you should never really have the revs increase significantly without the car accelerating. An excessively slipping clutch is a distinct feeling. The engine will rev, but the car doesn't accelerate. There are intermittent blips at times when going between D and R, but not revving up to 3k for no reason.

With the car being tuned, there isn't really a "normal" anymore. Everything is running out of spec and your clutches might be worn. That's not uncommon for tuned cars. A tune will ultimately shorten the lifespan of the powertrain components. The clutch packs in particular will wear sooner due to having to handle more than stock torque.

Thanks for joining in.

it did once at the stoplight. was slowing down then the light turned green then eased into the gas through the turn and the car shot up to 3k but wouldn’t accelerate for a split second.

I am not blaming your tune but that is certainly a variable, I am curious, did you change the fluid yet, I think it is due (if not mileage then the time mileage of 5 or 6 years)

Just realized you mentioned the transmission was serviced 10K miles (I guess by the previous owner) before but you can't confirm if the fluid level was correct or if the right fluid is used.

about a couple days ago i went out and was driving quite a bit like 2 and a half hours total and the car felt great shifting wise but on the way back home i took the same exact route its uphill ish for like 5 minutes and the car did the same thing as before at the same light. stopped a little too far above the white line so i tried to reverse back a little and the car shot up in rpms but wouldnt move. light turns green, i switch it into drive and did the same thing. rpms shot up to 3k and wouldn't accelerate for a split second.

at 50k even on the original ATF you'd be fine, I think you might be low a quart or so on fluid if this is a habitual thing. although yeah once a car is tuned I'm sorta leary just because you introduce a whole lot of new information and variables to the system

yeah i went out the other day and drove a decent amount around 2 and a half hours total and the car didnt hiccup once the whole day buton drive back i took the same exact route home as last time it goes up hill for around 5 minutes or so and the car slipped at the same exact light as before. stopped a little too far above the white line so i put it in reverse to go back a little and rpms just shot up to 3k and didnt move. light turns green, put it in drive same thing for a split second.

drove the car the other day for around 2 and a half hours or so and didn't hiccup once like the car shifted fine all day until i took the same route as last time back home it goes up hill for around 5 minutes and at the same street light it did the same thing again. rpms shot up to 3k when i tried reversing a little because i stopped a little too far above the white line. light turns green, put it in drive and same thing for a split second.

Sounds like a fluid level issue as forum member ChrisHimself mentioned.