1994 E320 Wagon
250,000 miles
original transmission (B3 friction discs replaced about 10K miles ago)
regular ATF fluid/filter changes since new

Over the last 6 months, car has developed slightly harsh upshifts, 3 to 4 shift seeems to be the worst.

I suspect vac mod or vac leak problem. Checked vac system for leaks by visual inspection and with Mighty Vac tool--none found, vac mod circuit will hold 15 inches of vac with no leakdown.

So my question: is it possible/likely that the vac mod is defective even if it holds vacuum?

I did try to reduce pressure slightly be adjusting the vac mod pin--harsh shifts still present. If anything, the adjustment resulted in a very slight flair in the 2-3 shift.

Thanks for reading.

J. M. van Swaay

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1994 E320 Wagon, 230,000 miles
1995 E320 Sedan, 106,000 miles
1994 E500 Sedan, 79,000 miles

Yes, the modulator could be defective & still hold vacuum.

Could also be that the engine is making less vacuum. (valve job?)
Is the compression still good?

__________________
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

Thanks for the response. I haven't done a compression check--engine runs strong and produces very adequate power. Valves were done about 70K miles ago when I did the head gasket. I do have a compression tester set up--I'll do a check next time I'm under the hood.

A new vac mod was about $40 last time I checked--maybe (against my better judgement) I'll try the throw parts at it and see if it fixes it approach......

J. M. van Swaay

__________________
1994 E320 Wagon, 230,000 miles
1995 E320 Sedan, 106,000 miles
1994 E500 Sedan, 79,000 miles