The big brown truck of happiness delivered my new Mityvac today. Now starts the quest to find the root of my clunking sound during the 2>1 downshift.
So far I have:
1: Connected to Mityvac to blk line going to modualtor. With engine at idle pumped up to 17"hg it held for 5min. So I assume line to tranny is go to go.

2: Connected to fitting between Vacunm pump and brake booster. Started engine. Reading at Mityvac was 21-22"hg. So belive vacunm pump and those line ok.

Got dark on me so I quit for the night. Have read most of the tranny articles like Steve Brotherton's etc. My next step is to test IP control/bleeder valve, but a little confused on where to hook up the mityvac. Do I go to top direct to valve? Or connect to green orfice? Do I pump up mityvac and see if it holds vacunm? Start engine? Or is it suppose to procuce vacunm on its own and give reading?

Sorry for long post, just wanna learn.

Andy

__________________
83 300D 169K (Mine)
86 F250 4X4 6.9 (Mine)
05 VW Passat TDI (Wife's)

This should help: http://transmission.articles.mbz.org/adjust/

I have the same downshift clunk in all gears on my 1982 300sd. I think it is a vacuum problem. One issue I have is the Switchover valve on top of the valve cover. My cam arm is worn out. I am not sure if this could cause the problem or not. Let me know what you find out.

willrev@earthlink.net

Check your front flex disk, too!

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

I think, I found the source of my leak. Hooked up mityvac to lines going to 3/2 valve, would not hold vacuum. Took cover off one of the rubber hoses was off. All looked old and came off too easy. So replaced all with closet size from Autozone.

This time mityvac would pump up, but would slowly come down, which leads me to belive that the 3/2 valve itself is leaking.

Just for grins I plugged the two (white and black) lines going to the 3/2 valve at the rubber Y connectors. And guess what: smooth postive shifts with no downshift ckunks.

I spent most of the afternoon doing, a fourm search on the 3/2 valve. and there seems to be a debate as to plugging the lines and bypassing the 3/2. Will this hurt the anything, or should I play it save and repalce both 3/2?

They seem easy to change (not as easy as pluggin lines) and not that expensive.

PS Peter, flex plates look ok, but will look close next weekend.
Willrev, try plugging those lines and see what that will do.


Andy

__________________
83 300D 169K (Mine)
86 F250 4X4 6.9 (Mine)
05 VW Passat TDI (Wife's)