1987 w124 transmission shifts at maximum rpm - PeachParts Mercedes-Benz Forum

mrmati · #1 10-21-2007, 06:35 PM

Hello everyone
Im having some issues with my transmission in my 1987 w124 300d (om603)
Basically what happens the transmission only shifts at maximum rpm (redline) no slipping or anything like that (on all gears). Other then the fact, that im first off from when the lights go green, it is pretty annoying, bad for the engine, and a waste of fuel, on the highway to get to the last gear I have to 150km/h (which in Canada is a pretty big offense now if one get caught, they take you car away!!! ) therefore I want to fix it or change it if worse come to worse, here are something’s I have in mind:

I have read some about the b2 piston and k1 spring kit ??? it probably would not hurt
in the case that the tranny is toast should I rebuild or buy a used one
would a 300e tranny work /adapt to the om603 engine?
what is the transmission number that should be in this car?
out of pure curiosity and sense of adventure would the 300e 5 speed work, what about the 190e since I have a brand new flywheel and pressure plate (original for the w124 300d) ?

Any other ideas? I love this car (freshly rebuilt new head, fresh injectors, timing chain, vacuum pump, engine runs beautifully no smoke even at max rpm! O yeah 500k on the clock), just this transmission issue,
Thank you for all info upfront

babymog · #2 10-21-2007, 09:49 PM

It sounds like the downshift/bowden cable is stuck or mis-adjusted. There is a bellcrank at the throttle cable connection that pulls the downshift cable as you add throttle, make sure it returns properly when at idle, possibly adjust it longer to see if it helps.

Where are you located?

sixto · #3 10-21-2007, 09:59 PM

Or the kickdown switch is stuck. Maybe the carpet or mat is bunched up in that area. Remove the switch and see if that restores normal shifting.

Sixto
87 300D

Brian Carlton · #4 10-21-2007, 10:07 PM

Quote:

Originally Posted by sixto

Or the kickdown switch is stuck. Maybe the carpet or mat is bunched up in that area. Remove the switch and see if that restores normal shifting.

Sixto
87 300D

Yep.........

Maxbumpo · #5 10-22-2007, 08:06 AM

Quote:

Originally Posted by sixto

Or the kickdown switch is stuck. Maybe the carpet or mat is bunched up in that area. Remove the switch and see if that restores normal shifting.

Sixto
87 300D

I'll second that "Yep"! Classic symptom...

mrmati · #6 10-22-2007, 03:27 PM

thanks for all the help
the kick down switch must have been the problem, I have unplugged it and works much better, i guess i will need to replace it.

moving on the transmission issue, i found that it has some problems shifting gears, its difficult to explain, its not slipping or kicking out when in gear just between 1-2 2-3 and a little between 3-4 gears, its like when driving a manual transmission car the driver instead of shifting puts it neutral and tries to to accelerate and a second later shifts ?! i cant really come up with a better way of explaining this issue

would this be the b2 piston? any hints?
thanks again matthew

ps anyone know if the w126 oil cooler would fit the w124 ? is it the same cooler/radiator? cant seem to find any info on this subject

Brian Carlton · #7 10-22-2007, 06:49 PM

Quote:

Originally Posted by mrmati

moving on the transmission issue, i found that it has some problems shifting gears, its difficult to explain, its not slipping or kicking out when in gear just between 1-2 2-3 and a little between 3-4 gears, its like when driving a manual transmission car the driver instead of shifting puts it neutral and tries to to accelerate and a second later shifts ?! i cant really come up with a better way of explaining this issue

The term that you are searching for is "flaring".

It occurs when the transmission sees too much vacuum. Connect a Mityvac to the transmission line (using a T) and drive the vehicle while observing the gauge. Report back with vacuum levels at various operating conditions.

mrmati · #8 10-23-2007, 02:42 PM

i dont have a Mityvac, ill pick one up on the weekend, anyway could you be more specific where to connect it? somewhere under the hood? or beside the tranny? am i suppose to run the hose trough the window into the car? by the way i have noticed that it shifts a lot worse when its raining!!! (would this be connected in some way to a vacuem leak, or more of a electrical problem?) by the way does the fact that the tachometer does not work, in any way connected to the tranny problem?

Brian Carlton · #9 10-23-2007, 08:48 PM

Quote:

Originally Posted by mrmati

i dont have a Mityvac, ill pick one up on the weekend, anyway could you be more specific where to connect it? somewhere under the hood? or beside the tranny? am i suppose to run the hose trough the window into the car? by the way i have noticed that it shifts a lot worse when its raining!!! (would this be connected in some way to a vacuem leak, or more of a electrical problem?) by the way does the fact that the tachometer does not work, in any way connected to the tranny problem?

Find the vacuum amplifer (the blue flying saucer). On the top of this device is a port called "trans". This line goes to the transmission. T into the line with the Mityvac and put the Mityvac through the window so you can observe it while driving.

I have no possible suggestion as to why is shifts worse in the rain.

mrmati · #10 10-23-2007, 09:24 PM

thats really wierd because the port that has "tra" on is disconected what is the color of the line that has to connect to it maybe the PO has one something !!! could someone post a picture of this ? please. I cant get under the car to see what vacuum line goes into the tranny until the weekend, (i have to take it to my as place, my tools are in his garage)