I have a W123-240D, it wants to shift into 4th gear at approximately 25 mph (actually it shifts into all gears too soon). The kick down switch does not work. I have checked the switch and it seems to be working by using a volt/ohm meter but not shifting the trans down. I have checked the vacumn going to the modulator valve and it holds fine. Just what are you adjusting when you adjust the modulator valve? Are you adjusting the amount of vacumn or something other than that? Do you adjust it IN or OUT and will this adjustment change the shifting points (speed)? When shifting it manually, it shifts great, nice and smooth. It engages both forward and reverse as soon as it is put into gear, so appearently no slippage.
Any suggestions/help would be appreciated.

Thanks,
Hugh

Vacuum modulator adjusts firmness of shift by acting on pressures within transmission. That's why a pressure gauge on trans is used when truly adjusting modulator. Sounds to me like you want to adjust shift timing, which is related to Bowden cable adjustment. (assuming 81-83 240D has a Bowden cable like my 300SD, and not a control pressure rod or some such).

For most of our diesels (can't speak for all models):
Firmness of shift... vacuum modulator
Timing of shift.......Bowden cable

Of couse the two form their own little feedback circuit to add an infinite # of possible adjustments.

Stevebfl has a great article on it here:http://www.continentalimports.com/ser_ic20242.html

__________________
The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)

I checked the article you mentioned. I found no mention of BOWDEN cable. I'm not sure the 240D is equiped with it. However, I'm new to the 240D so still learning.
I'm trying to find the info re: the Bowden cable you refered to.
In the looking/learning process...
Again thanks for your reply
Hugh

I am not disagreeing with the previous reply which stated:
firmness of shift depends on the modulator, and timing
of shift depends on the adjustment of Bowden cable.
I assume the Bowden cable is the one which hooks up
to the linkage atop the valve cover and goes into the
trans. However, this logic has not applied to my new
(said to be new, bought on ebay) transmission for my
82' 300sd. I am having very harsh 1-2 shifts.
There is a small improvement if I turn the modulator
adjustment screw counter clockwise, but have run
out of adjustment. It becomes backed out too far
to fit back in the slot. I get smooth shifts if the Bowden
cable is completely disconnected but it shifts through the
gears way too fast. I've tried various adjustments
on the cable and modulator but the end result is
either a harsh shift (especially 1-2) or a immediate
shift through the four gears, 2-3 sometimes takes
one second. I've also replaced the plastic piece on
the injection pump and adjusted for correct vacuum
bleed off. It seems to be a decision of whether I want
spilled coffee and high wear on the drivetrain or if
I want that challenge of merging on the highway
while the engine lugs in fourth gear at 1200 rpm. I could
downshift manually, but since this is a new (or I was
ripped off bigtime) transmission I expect better.
Perhaps I could have gotten more out of the trans
that was replaced-partly because of harsh shifts-
if I knew what to correct externally. Thanks in advance
for any advice.
Mark T. 82' 300sd

Hugh, Tell us what year 240 you have. The early 240s didn't have the cable, they had a control rod.

__________________
My Truck.. 2007 DODGE, 5.9 Cummins, 6spd stick, 4X4. My car..1977 240D, OTHER WHEELS...1955 VW Oval window bug, European Delivery (Holland) with a 1700cc, 2 barrel, Porsche drum brakes. 1939 WILLYS Pick-up. 1967 Triumph 200cc Tiger Cub. 1976 Honda 550F 4cyl Motor Cycle.

try the following link...

Tranny setup

Been doing fine adjustment this week and the pictures here helped along with the info from this site.

I just completed the adjustment of the vacuum bleed valve which sits on the back of the injection pump. This valve and the accompanying vacuum hoses are all we have on the 240D; there is no bowden cable on the '82 model year.

Fine adjustment on this valve will increase or decrease the range of vacuum leak to the modulator. The higher the leak the harder and later the shifts, the lower the leak the sooner and softer the shifts.

The link to continental imports helps, I also use Alldata DIY net for hose routings and adjustments to spec.

I also found it almost impossible to adjust the valve while on the IP, so I just removed it and adjusted it in my hand while making small adjustments looking at my vacuum guage. Also, you need to make some sort of 10mm spacer between the stop pin and lever.

Good luck.

Regards,

Jack

Thanks Jack
Did you take any pics? When you say "lower the leak" means slow to lose vacuum? What about the position of the actuating lever?

__________________
Jim

Hugh,
I have a 1980 300D without the bowden cable or mechanical linkage so I am not sure if this applies but here is what i went through on my car to correct my shifting problems. Much of it was trial and error after reading numerous posts on transmission adjustments.

http://www.peachparts.com/shopforum/showthread.php?threadid=56404

__________________
'99 S420 - Mommies
'72 280SE 4.5 - looking to breathe life into it
'84 300SD Grey - Sold
'85 300SD Silver - Sold
'78 Ski Nautique

What I mean by "lower the leak" is that the vacuum valve on top of the IP is used to increase and decrease the vacuum to the transmission modulator. The adjustment on the valve increases or decreases the "range" of the vacuum bleed througout the movement of the vacuum valve lever. When the valve is positioned at full throttle it provides the least vacuum to the modulator ( highest leak ) and when the throttle is at idle it provides the most vacuum to the modulator ( lowest leak ).

Since this was my first experience with this type of repair, I read all I could on this message board. I believed that if I removed all vacuum from the vacuum modulator, I would be able to troubleshoot the transmission shifting problem I was having. ( the transmission never shifted into 3rd). What I learned, was that it is true that all vacuum is removed at full throttle, but prior to getting to full throttle on the 240D the vacuum valve shifts through all gears smoothly with the aid of regulated vacuum.

BTW, I don't have a way to take or post pictures, but if you do a search on this board for transmission vacuum valve, etc. many links and pictures are available that dicsuss that discuss the adjustment of the vacuum valve.

Thanks to all on this board for the many messages and help. Since I am new to the board. I have been a 1982 249D owner since 1983 when I purchased it used in Atlanta. The vehicle has been our pride and joy since then and I have learned to do almost everything to maintain this vehicle. Started with 35k miles and now have 211K miles.

The only problems I can't seem to overcome are the constant leaking (blowing) of oil from the valve cover Bypass port. Also, the AC has never worked well, after chaning over to R134, it worked for awhile and then quit.

Again, Thanks for all help.