Hard shifting on slower acceleration

Okiebenz · #1 06-18-2002, 08:23 PM

After I recently had the Control Pressure Cable replaced on my 1994 C220, the shifts to 2nd and 3rd are very harsh on slower accelerations and OK on fast acceleration. A little research, including this forum, suggests the vacuum modulator needs adjustment. My question is whether this is related to or independent of the Control Pressure Cable and any adjustments or calibrations needed after its replacement. Also, is it necessary for a shop to have special pressure gauges for this procedure or can it be done by "feel" and multiple trial adjustment?

Thanks,
Okiebenz

jsmith · #2 06-18-2002, 08:28 PM

what are the rpm's when you feel the harsh shifts at slower acceleration? i had this problem on my car and was able to eliminate it by adjusting the control pressure cable to make it shift later at part throttle.

Okiebenz · #3 06-20-2002, 04:50 PM

It occurs at very low, e.g. sub 2K, rpm in my wife's style of driving which involves very slow acceleration. The shop that installed the control pressure cable tried that adjustment with little improvement.

jsmith · #4 06-20-2002, 08:48 PM

If they adjusted it correctly, then it should shift at a higher rpm under part throttle where it should shift more smoothly. Didn't you say that it shifts more smoothly at higher rpm? I think at the lower rpm there may not be enough vacuum for the modulator to do its job - just a conjecture though.

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