vacuum testing for transmission (300d ~1983)
03-09-2007, 08:52 PM
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vacuum testing for transmission (300d ~1983)
first post here-
I'm helping a friend, trying to get his transmission to shift like a normal car.
a little background:
just installed a used transmission (automatic)
has new:
vacuum switch at throttle
booster hose
yellow lock control vacuum valve thingy
no vacuum leaks at trans modulator, heater control, lock control, ignition switch.
vacuum pump holds easy >20 inches
vacuum at the throttle valve (leading to trans mod) is 13 inches at idle, drops to under 9 if you snap the throttle.
the car itself I think is a 1983 300d no turbo 4 door. it has small bumpers and I'm told it's 'gray market', for what that's worth.
one problem is that I don't understand the function of the vacuum unit (2 ports, white) located at the top and rear of the injection pump.
if I fiddle around with different things I can get the transmission to shift fine under heavy throttle, or light throttle, but not both.
it'll either shift very late, slip in 2nd, not kick down.
or some, but not all combinations.
if someone could explain or point me to info on the vacuum unit on the injection pump, or let me know what kind of vacuum signal to expect leading to the transmission mod under all conditions.
I've run a saab repair shop for near 20 years, but I'm out in the cold when it comes the the benz, or automatic transmissions. so I know a bit about working on cars, but not this one.
thanks for taking the time to read this post,
-dan
santa cruz, ca.
ps - if I've been vague about the car or it's components, just point out what I didn't explain and I'll do my best to find out. I can take photos if needed.
thanks again.
edit: the closest vacuum diagram I can find that seems to match this car is here : http://home.comcast.net/~phantoms/vacuum/engine.jpg
I'm helping a friend, trying to get his transmission to shift like a normal car.
a little background:
just installed a used transmission (automatic)
has new:
vacuum switch at throttle
booster hose
yellow lock control vacuum valve thingy
no vacuum leaks at trans modulator, heater control, lock control, ignition switch.
vacuum pump holds easy >20 inches
vacuum at the throttle valve (leading to trans mod) is 13 inches at idle, drops to under 9 if you snap the throttle.
the car itself I think is a 1983 300d no turbo 4 door. it has small bumpers and I'm told it's 'gray market', for what that's worth.
one problem is that I don't understand the function of the vacuum unit (2 ports, white) located at the top and rear of the injection pump.
if I fiddle around with different things I can get the transmission to shift fine under heavy throttle, or light throttle, but not both.
it'll either shift very late, slip in 2nd, not kick down.
or some, but not all combinations.
if someone could explain or point me to info on the vacuum unit on the injection pump, or let me know what kind of vacuum signal to expect leading to the transmission mod under all conditions.
I've run a saab repair shop for near 20 years, but I'm out in the cold when it comes the the benz, or automatic transmissions. so I know a bit about working on cars, but not this one.
thanks for taking the time to read this post,
-dan
santa cruz, ca.
ps - if I've been vague about the car or it's components, just point out what I didn't explain and I'll do my best to find out. I can take photos if needed.
thanks again.
edit: the closest vacuum diagram I can find that seems to match this car is here : http://home.comcast.net/~phantoms/vacuum/engine.jpg
Last edited by dan_j; 03-09-2007 at 09:00 PM. Reason: more info
03-09-2007, 09:49 PM
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Have you tried adjusting the valve on the transmission vacuum valve? This
is simple, remove the cap , use needle nose pliers or other
suitable tool to pull adjuster screw out of its seat, screw counter clockwise
for quicker shift, clockwise for later shift.
is simple, remove the cap , use needle nose pliers or other
suitable tool to pull adjuster screw out of its seat, screw counter clockwise
for quicker shift, clockwise for later shift.
03-09-2007, 10:03 PM
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well, kinda.
before I realized the throttle switch needed to be replaced I did 'mess' with it a bit trying to get it to shift sooner.
I won't be able to get back to it for a few days, knowing I should return it to where it was.
but I just don't understand how the vacuum control should operate, or what values to expect when testing them.
but your right, the transmission control valve (modulation ?) should be set back to where it was.
I took a few snaps, see here http://picasaweb.google.com/danjoel/...21559053678690
before I realized the throttle switch needed to be replaced I did 'mess' with it a bit trying to get it to shift sooner.
I won't be able to get back to it for a few days, knowing I should return it to where it was.
but I just don't understand how the vacuum control should operate, or what values to expect when testing them.
but your right, the transmission control valve (modulation ?) should be set back to where it was.
I took a few snaps, see here http://picasaweb.google.com/danjoel/...21559053678690
