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  #1  
Old 01-27-2011, 10:42 AM
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Join Date: Jan 2005
Location: St. Louis Missouri
Posts: 473
722.369 vac mod question

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
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  #2  
Old 01-27-2011, 10:56 AM
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Join Date: Mar 1999
Location: Tucker, Ga USA
Posts: 12,153
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?
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  #3  
Old 01-27-2011, 09:26 PM
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Join Date: Jan 2005
Location: St. Louis Missouri
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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
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1994 E320 Wagon, 230,000 miles
1995 E320 Sedan, 106,000 miles
1994 E500 Sedan, 79,000 miles
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