Weird transmission Vacuum Problem 1984 300SD
 

Ok this one has me puzzled. I checked vacuum going to the transmission (unplugged black line and replaced with vac gauge.) I got a steady 21 inches no matter where the throtte was. I removed the round green surge damper and I get 12-2 like I should (12 @ idle 2 @ WOT) and the transmission shifts much better.

So I look at the surge damper, I can blow through it and pull a vacuum through it both directions. So why when this surge damper is installed, I lose my 12-2 vacuum going to the trans?

Anyone?

I did not know what the green thing was for but this is an excellent question. Hope someone knows; I do not. But I certainly know how to adjust the vacuum modulator, vav lever, and vav nut under the plastic dome. Got my new tranny almost completly straightened out - 81 300SD.

Good luck - hope someone has an answer. Bet Steve Brotherton knows.

it is just that - a damper. When vacuum changes suddenly, it smooths out the change so the trans gets an even signal that is better timed and not so 'touchy'.

it is a dashpot, it damps pressure fluctuation. It only 'decreases' flow under severe changes in pressure or vacuum. It does not restrict flow when flow is constant.

the only reason it could be disturbing your vacuum levels to that degree is:

-contamination
-bad rubber connections
-broken (ie.. the plastic somewhere has a crack)

I also do not understand why your vacuum increased with it installed. The way you measure has a great affect.

also, did you remove any other parts with it? (...a 'Y' or a colored plastic insert)

Did not remove the orifice (sp?) the I pulled the black line going to the trans modualtor and hooked up my vacuum gauge. I might clean it out with brake cleaner and reinstall to see what happens,,, will keep you posted

OK Cleaned it out with soapy water, reinstalled and I have 12-2 again! Hopefully I've also eliminated the occasional "Clunk" when letting up off the accelerator pedal.