automatic transmission malfunction

[pep]

My sl500 auto transmission has a peculiar shifting. The second gear takes longer to shift and it does it on and off, sometimes shift ing great and others taking longer to shift or hard shifting. I changed the trans fluid, but it hasn't improved its condition. The other gears work well. Need help, I don't want to replace the trans and don't want to go to a trans repair place without an idea of what's going. IT is a SL500 Roadster 1994 with 88000 miles.

[400E]

MB transmissions, at least those from the 1990s, have an upshift delay built in to delay the 1-2 (and maybe 2-3) upshift until the engine warms up, as an emission control strategy. Is this by any chance what you are observing?

[pep]

It could be, but it does it whether on and off after the trans is warmed up. Specially as I stop and turn either left, or right. Its like something works right and then wrong, no steady shift pattern. Thank You for the rapid replay 400E. PEP

[ejsharp]

This is only a guess but because it is intermittant and effected by centripical force I would look for a loose or corroded connection... possibly at the temperature sending unit.

[pep]

I forgot to relate to you that I was told the modulator valve could be malfunctioning or the vacuum line might be obstructed. I'm going to check for a corrosive connection at the temperature sending unit and then, do you suggest I should go the modulator valve route and replace and how do you replace the valve? Thank You for your help. PEP

[stevebfl]

The modulator has very little to do with the shift timing. It is in control of shift pressure (which is then used to make control pressure, so modulator pressure does eventually effect shift timing).

The delay for catalyst warming is made by applying vacuum to a bellcrank mechanism that changes the effect of the control pressure cable. You might locate and disconnect this vacuum and plug it. This would keep tha cat heating delay from happening and set a check engine light eventually. It will eliminate this possible defect though. I have never seen it happen but if the vacuum gets through to the control element it will change the shift profile.