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SLK230 transmission issues

11K views 23 replies 9 participants last post by  Mn car guy 
#1 ·
I just bought a 2001 SLK230 and it has not been taken care of. On my first highway drive I was pulling 4000 rpms at 60mph. Thought that was high. Then the next day I took it out again and was pulling around 2200 rpms at 60mph. Much better. Then after taking off from a red light it went back to 4000 at 60mph. Did the transmission reset and it was back to 2200 until taking off from another red light awhile later. Any idea what is happening? I'm stumped.
 
#3 ·
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#4 ·
#6 ·
I just bought a 2001 SLK230 and it has not been taken care of. On my first highway drive I was pulling 4000 rpms at 60mph. Thought that was high. Then the next day I took it out again and was pulling around 2200 rpms at 60mph. Much better. Then after taking off from a red light it went back to 4000 at 60mph. Did the transmission reset and it was back to 2200 until taking off from another red light awhile later. Any idea what is happening? I'm stumped.
Try this and use the proper grade gasoline

http://www.slkworld.com/general-discussion/70666-reset-transmission-adaptive-learning.html
I did this and it worked fine till a bit down the road when I had to come to a complete stop for a red light. After take off it was back to pulling 4000 rpms at 60mph. Does it require multiple resets?
 
#7 ·
no only 1 reset

do a transmission service if you have no idea when it was done last
 
#9 ·
First and foremost, you need to check for transmission fluid wicking through your "pilot bushing" into your wiring harness and further into your transmission computer. The pilot bushing is where the wires enter your transmission, it's a plastic electrical connector with rubber seals designed to prevent fluid leakage. They frequently go bad, and when they do, transmission fluid will wick through your wiring harness all the way up to your transmission computer and cause all kinds of weird behavior. You should inspect your bushing from under the car - feel for any oily fluid on the wires. Next pull your passenger carpet back, remove the styrofoam, free your equipment bridge (3 10mm plastic nuts) and lay the bridge down in the floorboard so that you can see the yellow padding. If the yellow padding has any red stains near the wires - bingo - replace the pilot bushing. You might be able to salvage your transmission computer by disassembling and cleaning it, but usually replacement is required once it gets to this. It's a straightforward swap, no coding or computer work required.

I've also had to replace a conductor plate to straighten out one of these transmissions - this just adds a few extra minutes to a transmission service. IIRC these plates cost about $100 USD and are very easy to replace - again with no coding or computer work required.
 
#13 ·
I was thinking the same thing. Are you inadvertantly selecting manual mode? You have a gear indicator on the dash. If you are in fully automatic mode, it will say 'D". If you've bumped it to manual, it will read the gear number you've selected. I'd start here though it also makes sense to service the trans especially as it's history is somewhat unknown.
 
#19 ·
You don't say how many miles are on the car.

Automatic transmissions on Mercedes cars from the late 1990s to about 2007 or 2008 are often left un-serviced, even by the dealership service teams, because MBZ removed the transmission service entry from the recommended service list for those years in order to compete with other car makers' claim of "No service required!"

The automatic transmissions should *always* be given a lubrication service at 40,000 mile intervals (drain old, contaminated oil, replace filters, refill). Most of the transmissions will last through two missed transmission services, but a large number of them then have transmission problems starting around 100,000-115,000 miles. This usually means a $4K to $8K transmission replacement, for any shop where the mechanic is unwilling to overhaul the old transmission at a reasonable rate; they just replace it with a new or remanufactured transmission. (A good shop and a knowledgeable mechanic can usually do an overhaul on the bench for around $3K or so, but this is becoming rare to find because it is quite time consuming to do and locks up a service bay while the car is apart...)

The behavior you describe sounds like it could be one of or a combination of a couple of things:

  • gear selection mechanism clogged up and working inconsistently
  • valve body damaged or worn
  • clutch packs in the transmission worn out
  • insufficient fluid level or clogged filter not allowing trans to maintain proper operating pressures for the mechanism

The very first thing to do, however, is to pull a sample of the transmission oil and examine it for current condition. If it smells burnt, it's at least worn out. If it feels gritty or larger bits of metal/friction material come out with it, and the mileage is high, the likelihood is that the transmission needs an overhaul. Changing the oil and filter could restore consistent, proper operation for a while, but depending upon mileage, it might not last long.

My SLK280 had 85,000 miles on it when I bought it. I had the automatic transmission oil checked when I had the pre-purchase inspection done. It smelled slightly burnt and very slightly gritty, but analysis showed no metallic content and the shifting seemed sound. I had the transmission service done immediately after buying the car, with an extra flush of fresh oil, and no significant crud came out. Since I did that, the transmission's behavior has been transformed: it feels like a different car, shifts consistently and crisply in both C and S modes, up and down shifts manually perfectly. Even the service is somewhat expensive (about $700) but once every 40,000 miles is well worth the price—it should allow the transmission to last 300,000 miles or more.

Good luck with it! Take it to a qualified Mercedes-Benz independent shop ... they'll generally cost a lot less than the dealer and often give better, more informed service.

G
 
#20 ·
So I ordered a new conductor plate and tranny fluid for my slk230. Just got to thinking and I bought this car with 20" rims and low profile tires. Could the change in size be what's causing my tranny to shift at higher rpms? I planned on putting stock wheels and tires on it anyways. Should I do this before I change out conductor plate to see if it helps?
 
#23 ·
P0500 P0700 and P0101

P0500 is a general OBD-II code that indicates a malfunction has been detected in the vehicle speed sensor circuit. .
P0700 is a generic OBD-II code that is indicating a fault within the transmission control system

I think this is a strong clue why your transmission is acting strangely. I would investigate P0500 first.
 
#24 ·
It's hard to diagnose stuff on the internet but the codes help. You mentioned the car has 20's. Were they put on fairly recently? It's possible that whoever did it damaged a wheel speed sensor. Below is an article on how to replace them. It's still possible that you have a bad shifter. It's signigicant that you can't select manual mode. Id suggest you do the following. You've already bought the stuff for the tranny fluid change. Go ahead and do that as it's good long term preventative maintanance. Then I'd use your scan tool to reset the codes. Then take it for a drive and see how everything works.

If you're still getting shift issues, I'd take it to a dealer for diagnosis at least. Otherwise you could wind up throwing lots of unnecessary parts at it. Good luck.

Mercedes-Benz SLK 230 ABS Wheel Speed Sensor Replacement | 1998-2004 | Pelican Parts DIY Maintenance Article
 
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