HELP!! I have had harsh shifting problems since owning this 1980 300 SD 116 even after having the motor and transmission from an 81 300D installed and having the transmission rebuilt ($$$) by a good shop. After reading various threads about this problem, I have determined that:1. The vacuum valves that reside on the valve cover(EGR and throttle position)are not working correctly. The EGR is not a factor since its vacuum supply has developed a plugged line. And, 2.There was NO vacuum going to the transmission.
Using my trusty Mitivac,I found that the throttle position valve would reduce the vacuum to zero at the slightest touch of the throttle mechanism.
Defective valve?? There is a connection on the vac control unit on the IP that is on the fender side and below where the "snubber" goes into the top. When I disconnect and plug this connection the vac goes to about 12 in. Applied to the transmission line the 12 in of vac results in silky smooth shifts,also increased power(or is that just my imagination). At this point the 12 in is being fed to the transmission and to the "snubber only. What I am calling the snubber is the green cylinder shown in the pic. Question: will a constant 12 in to the transmission cause any problems? Anyone?? The Poor Soul would really appreciate any input you might provide to avoid any potential problems and to further his MB education.Thanks in advance, Willie(Poor Soul)

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