Ken Silver

Still getting to grips with my month-old 2003 SL600, and as I've become more acclimatized to it, I've noticed a peculiar hunting in the gearbox.

It happens mainly at low speed on a gentle uphill incline at around 1500 rpm, and it feels like the automatic can't make up its mind what gear to change to. From outside, with the top down, the engine sounds constant, but inside it's like a slipping clutch all the time.

I've tested with Sport and Comfort settings, driven both gently and agressively at times to fool the computer, but it still happens.

Also I've found it difficult to take off smoothly. It's always too much or too little accelerator.

Is there something I'm missing? The car went through a pre-purchase check with top marks, so seems to mechanically OK.


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~2003 SL600, black/black
~1999 SLK 230 silver/black
~2007 Lexus LS600hL, 5 seat, black/black
~2004 Lexus RX330 silver/black

Ausmbtech

Sounds like you may have coolant in the transmiision oil. Pretty much never heard of in a R230, very common in W203/209/211.

I would suggest you get a oil sample tested by your dealer (most dealers have test kits they either do in house or send for analysis) to see if you have coolant in the transmission oil. It doesn't matter if you do or don't have coolant in the oil, you need to know what you're dealing with ASAP and it's the cheapest way to find out.

Basicly the "hunting" is not the transmission changing gear, it's the torque convertor clutch slipping excessivly then grabbing. Basicly it's fluctuating friction levels of the clutch in the torque convertor and the transmission ECU can't work out what to do about it.

If you have coolant in the oil then that's the cause, if you don't then get back to us and i'll let you know the other possible causes.

Ken Silver

Well that's interesting. If you say it's rare in the R230 - and this one has been meticulously maintained with only 38,000kms - what are the other likely causes?

DeLorean00

I do not own a SL600 but I have a 2003 SL500 and I get annoyed at times with my automatic transmission. Not exactly what you are talking about, but just doesn't all feel perfect. And my car is a Certified Pre Owned from Mercedes-Benz.

Ausmbtech

How well it's maintained has no bearing on wheather the radiator fails causing coolant to enter the transmission.

If it's not coolant then you would probably start by checking if there is new transmission software (if programmable), performing the adaptation (learning) of the lockup clutch, if still playing up then it may be a physical fault in the valve body, a fault in the transmission ECU (the problem ones are identifiable by the part number), of the lockup clutches are damaged which would nessecitate a transmission removal to rectify.


Start with a check for coolant, if there is coolant then it can destroy the entire transmission if there is enough in the transmission and left in there long enough. Cheap piece of mind to know you won't have a bigger problem later.

IngenereAMG

You might be low on transmission fluid. I would start with the basics and work from there. The easiest thing to do is bring it to the dealer and have them check it out.

Ken Silver

Thanks all, I'll be booking it in tomorrow.


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~2003 SL600, black/black
~1999 SLK 230 silver/black
~2007 Lexus LS600hL, 5 seat, black/black
~2004 Lexus RX330 silver/black

jagass

Whoa, that really sucks...

jagass

It was just only month-old?...

mlandis

I'd imagine that means month-old -- for Ken....

Ken Silver

It's booked for Wednesday. The techs didn't seem to have experienced this problem before.

I did hear one guy say that the SL600 accelerator has always been sensitive, a result of the drive-by-wire setup. It certainly accelerates much more differently than any other car I've driven. Sometimes I feel like a beginner again trying to avoid a bunny hop. (That was 47 yrs ago though!)

We'll see...


--------------
~2003 SL600, black/black
~1999 SLK 230 silver/black
~2007 Lexus LS600hL, 5 seat, black/black
~2004 Lexus RX330 silver/black

Ausmbtech

The throttle is different from most cars, but the hunting of the transmission isn't normal at all. Having so much torque should make it very smooth because it has very little need to change gears

Rook3300

I do recall when I first drove my SL500, I found the throttle to be a little sensitive. Of course, it didn't help that I was moving from a 140hp 4-banger Civic to the 302hp V8! I did find that the transmission was in Sport mode which made off-the-line starts a little touchy. Perhaps you should switch it to Comfort mode and get acclimated to the throttle then try Sport mode once in a while. Keep in mind that the transmission computer has to learn to adapt to your driving style and the previous owner may have liked to jackrabbit it off the line. You don't, so it'll have to learn that.

My Civic had throttle-by-wire which wasn't too sensitive at all. So not all systems are like that.

On the transmission hunting, it definitely should not be doing that at all. The torque in that engine is enough to pull down a house, so climbing an incline while holding a gear should be no problem at all. Do let us all know what the techs find out.

Rook

Ken Silver

I'm used to all my previous MB's - SL500 R129, SLK 230, 350SL, 230E, 280E etc - having a late throttle. You put your foot down, there's a lag, then the car moves off fast or slow depending on how deep you pressed the throttle. My Lexi are the same.

The SL600 is nothing like that and it is taking a lot of getting used to. However, as you note, the subsequent takeup is very smooth and powerful.


--------------
~2003 SL600, black/black
~1999 SLK 230 silver/black
~2007 Lexus LS600hL, 5 seat, black/black
~2004 Lexus RX330 silver/black

Ken Silver

For the first week - until I figured out how to set Sport and Comfort, I was unwittingly in Sport. But the last couple of weeks I've been using it solely in Comfort.

Don't know whether I can tell any difference, and I'm reluctant to change it back to Sport in case it messes with the transmission memory.

I'm really after a smooth and consistant ride. But I also like to unleash the beast every once in a while too... it really is a VERY fast car and a lot of fun!


--------------
~2003 SL600, black/black
~1999 SLK 230 silver/black
~2007 Lexus LS600hL, 5 seat, black/black
~2004 Lexus RX330 silver/black

Rook3300

It doesn't do anything to the transmission memory to switch back and forth. As a matter of fact, just yesterday while running errands, I must've switched between Sport and Comfort modes at least three times. When I get into the heavier-traffic parts of town, I like the quicker throttle response of Sport mode to allow traffic "sharking" (as I call it). There is difinitely a noticable difference between Comfort and Sport, but only if you are launching from stop lights or trying to pass people. During normal everyday driving (depending on how you drive normally), there's not much difference.

Just make sure that when you do switch, you are either parked or at a complete standstill. Otherwise, you'll get a weird hitch and pause as the TCU tries to figure out if you should be in a different gear or not. I did switch it once while moving (by accident) and won't do it again as it scared me into thinking something was wrong with the transmission.

Rook