A Little Help from the experts would be nice!
My 83 300sd is shifting hard (neck snapping - wheel squawking) 1-2 and 2-3 and when cold it starts in second and not first gear. When warm it starts in first but has the hard shift, The shift points are fine. I have checked and recheck the vacuum system for proper operation and I am sure it is OK. I checked the modulator and it holds vacuum. But here is where the problem is, I can put full vacuum or disconnect the vacuum line to the modulator and the shift quality does not change. I thought that someone might have adjusted it too tight so I have back out the adjustment but problem is still there. Do these valves freeze up or internally stick, or is it possible that the piston it the Trans has stuck?
Regards,
Bryan

At idle there should be approx 15" vacuum at the modulator. This is controled by a vacuum valve on the valve cover & another vacuum valve on the injection pump.

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

Yes I have 15hg of vac at the modulator at idle and it slow drops with throttle posistion. 7.5 @ half throttle and 0 at full. Its operation is smooth. There are no vacuum leaks. I checked the system from top to bottom and found it to be OK. This is what leads me to belive that the modulator or piston in the trans is internally stuck. I ordered a new modulator and I will check the valve in the trans as well as I have run out of logical answer