transmission slow shift between 2nd and 3rd - PeachParts Mercedes-Benz Forum

oldblue1 · #1 10-22-2002, 09:58 AM

I recently purchased a '90 300SL with 70K miles that has a transmission that appeared to have minor issues, but looks like it might be more than that. Please excuse my non technical desciption of the problem...

Two symptoms exhibited, one was slipping or RPM increase between 2nd and 3rd shift, the other was the "known" slow shift between 2nd and 3rd to warm up the catalytic converter. (and thus I was led to believe that it was normal). I was also told the pressure was a little low on the transmission/valve assembly. The service records indicated that this has been going on for some time. As the car has low milage, I thought it might need to be driven for some long trips and have transmission oil change before and after. This was done...problem still exists.

The slipping was easy to correct, there was an issue with the "clutch" bands, but the shift remains slow, even after you have driven the car for 2 hours or more, so it should be warm or even hot!

If you stop, whether for a traffic signal, or switch off, for any period of time, even less than a minute, the transmission does not want to shift from 2nd to 3rd as smoothly or as easily as the subsequent shifts or transitions. If you do not floor the accelerator, it will normally make the shift around 3500 to 4000 RPM, whereas the other gears shift in the 2500 RPM range. If you floor the accelerator, it will red line (not good).

I have read conflicting opinions on this, normal/not normal etc. I have consulted with a local transmission specialist who is also puzzled by this.

Apart from this, the car seems fine, no noises, no grinding, no problem with reverse, once on the open road or past 3rd, she goes like a dream!

joe p · #2 10-22-2002, 11:03 AM

shorten the bowden cable about 4 turns and see what it does.

Joe

oldblue1 · #3 10-23-2002, 09:16 AM

Thanks for the tip Joe.

Looking through the service records this seems to have been done. The tech at that time suggested that the next step was to change the valve assembly. We will try it again though.

During the latest work on the tranmission the clutch plates were found to be flaking. All the plates and various seals, O rings etc. have just been replaced. The Valve assembly was inspected and looked fine.

This is a 5 speed auto tranny with the part id of xxx 500 xxxx, if this helps anyone. I cannot find any record of it having been replaced. (the vehicle only has 70K and has been sitting for most of the last 5 or 6 years...probably when this problem started to develop...around 60K)

Could this be an electornic component that is failing?

jsmith · #4 10-23-2002, 10:30 AM

if the valve body is replaced, there is no guarantee that it will be fixed, there is the possibility that they may have to do further adjustments on it . this is additional labor because then they will have to drain ATF and open it up again. the bowden cable adjustment is the most obvious adjustment since that is supposed to adjust part throttle shift points. just keep track of the adjustment & do it in slow increments...

oldblue1 · #5 11-12-2002, 11:38 PM

OK, I am still having trouble with this tranny staying in 2nd for much longer than necessary.

I have had the unit rebuilt, checked and set the Bowden cable, checked the solenoid that apparently controls this first shift, all seem ok.

The first time I take it out, it just will not shift until its RPMs get way on up there 4500 or higher. Doesn't change by the time ALL my other cars do on the same section of road.

Once I can get it to shift into 3 and subsequent shifts 3 -4 and 4 -5 are smooth.

If I stop at a light, the next 2 -3 shift is smooth, around the 2500 - 3000 range. Transmission shifts into 5 easily around 55 - 60mph and drops right down to about 2200 RPM.

If I switch off the engine for less than 5 seconds the first change is still good, but if I SWITCH OFF FOR LONGER THAN 5 SECONDS, it reverts back to this long shift between 2 and 3.

Is there some timer that controls this shift as well as the RPM and Temp.,

Could it be that the is a sensor that is not working correctly and it is reset after this short switch off period?

One more thing, it sounds like the fuel pump does not switch off or cycle down during the times I am at idle, does this signify some controller problem that might be at fault and these are just the symptoms of it failing?

Also, I have read elsewhere that the 300SL, although not as good as the 500SL, is not that sluggish when you floor it...this car seems to drag just a second or so before kicking in, is this normal? Can this be also tied to the tranny issue?

It is driving me nuts!

oldblue1 · #6 11-29-2002, 09:28 PM

When my SL's tranny was recently rebuilt, we found the clutches were worn and/or flaking.

Replacing the clutches resolved the flaring.

Now it is only the delayed upshifts that are the problem.

Hocky · #7 11-30-2002, 05:03 AM

Sorry to hear that your tranny does the things you described. Mine is a C180 and it gives you this huge wake up call only in the morning or the first drive out whether morning or not. After that, all goes well and you wouldn't suspect anything. I'm surprised that yours goes back to the same drudgery after more than a 5 second stop of the engine. Maybe its something more serious there going wrong? For me I just need more power than what this 1799cc engine can produce. I should have bought at least a C220 or the C280. Who knows, maybe the 2002 C180 Kompressor will make me happier.

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