Transmission not up-shifting to third - PeachParts Mercedes-Benz Forum

inventor · #1 07-13-2009, 10:33 PM

Hi, I have a 1981 300SD turbo 240.000 and for the last month the trani refuses to shift up to third, first second shifts very smoothly and on time but no third I tried the pumping and ez on the throttle but it refuses to up shift.

So far I have tested and checked this,
1: vacuum tests all test 20 on all the orifices.
2: vacuum valve 3/2 levers are worn out but still working, Half throttle, half vacuum. Full throttle, no vacuum.
3: nothing is liking.
4: oil level good, red, no smell.
5: throttle linkage no slack.

Is anything I'm missing or overlook?

I read this threads to:

http://www.dieselgiant.com/trannyleverreplace.htm

http://www.peachparts.com/shopforum/showthread.php3?t=105297

http://www.mercedesdismantlers.com/AutomaticTransmissionInformation.html

thanks

kerry · #2 07-13-2009, 11:12 PM

Check your kickdown switch and bowden cable. When you say it won't shift to 3rd, how high an rpm have you pushed it to to try to get it to shift?

inventor · #3 07-13-2009, 11:50 PM

25 MPH at 2900 to 3000 and then push to 3000 to 3400 with no result.

Check your kickdown switch and bowden cable?

inventor · #4 07-14-2009, 12:06 AM

Update.

I don't know what is the kick down switch but the bowden cable is working OK as far as I know.

tbomachines · #5 07-14-2009, 12:24 AM

Quote:

Originally Posted by inventor

Update.

I don't know what is the kick down switch but the bowden cable is working OK as far as I know.

The kickdown switch is underneath the accelerator pedal. Unplug it. The Bowden cable should be intact, but you need to adjust it. It is on the throttle linkage where you can screw a little white collar to tighten it. Take all the slack out of the system and then try. Search "Bowden cable adjustment" on here and you should get some good results.

inventor · #6 07-14-2009, 12:30 AM

Yes thanks I will give that a try.

inventor · #7 07-14-2009, 12:40 PM

OK the kickdown switch is unplugged and there was no slack on the throttle cable. The problem is still there.

kerry · #8 07-14-2009, 01:00 PM

If the bowden cable mechanism is stuck it may still shift at higher rpm's than what you've tried. I'd go higher to see if it will shift. I'd also try manually shifting it up thru the gears.

inventor · #9 07-14-2009, 01:55 PM

Quote:

Originally Posted by kerry

If the bowden cable mechanism is stuck it may still shift at higher rpm's than what you've tried. I'd go higher to see if it will shift. I'd also try manually shifting it up thru the gears.

The Bowden cable is moving freely it dose not uppers stuck. I tried adjusting the throttle and got up to third, shifting at 3400 rpm i tried higher rpm (4200) no shifting, I knottiest something funny happening here if I'm revving it up to make it shift and let go of the peddle the eng cuts off and upon restarting it the trani is behaving normally for a wile this phenomenon happen several times in the pass three weeks, but it goes back to not shifting sudden.

inventor · #10 07-17-2009, 07:36 PM

To all the good people that care to help in this forum this is what happen so far.

The problem is still there no up-shifting to third.
Note: sometime it works for 100 mile round trip but then it acts again.
I check the vacuum and is 20 on all orifices.
Changed the vacuum valve levers.
Un-plug the kick down switch nothing change.
un-hook the bowden cable and it make no difference.
Adjusted the bowden cable 50 times but I don't know if I'm making any difference.
Manual shifting don't work at all.. any other suggestions appreciated.

kerry · #11 07-17-2009, 07:48 PM

Does adjusting or removing the bowden cable change the 1-2 shift. It should. If it doesn't something is not working right with it. Have you looked at the transmission end of the bowden cable to see what is going on there?

Actros617 · #12 07-17-2009, 07:55 PM

How about changing your tranny oil filter, it may be clogged with crud preventing the tranny to create enough pressure to up shift in to 3rd gear and on... Tell me how dose your transmission shift from 1-2, is it smooth, rough, Slip, Flares?

inventor · #13 07-17-2009, 07:57 PM

Quote:

Originally Posted by kerry

Does adjusting or removing the bowden cable change the 1-2 shift. It should. If it doesn't something is not working right with it. Have you looked at the transmission end of the bowden cable to see what is going on there?

No that is what I notice I disconnected the cable [and it dose have tension to it] and nothing change so I will check that next.
BTW I don't know if the stick and cable are related because it don't make any difference if I shifted up or down.

inventor · #14 07-17-2009, 08:06 PM

Quote:

Originally Posted by Actros617

How about changing your tranny oil filter, it may be clogged with crud preventing the tranny to create enough pressure to up shift in to 3rd gear and on... Tell me how dose your transmission shift from 1-2, is it smooth, rough, Slip, Flares?

The trani shifts like this if and when it works, it shifts smooth around 2100/2400 rpm 1-4 and when is not working is shifts smooth 1-2 and 50% at the time to third, no kicking ever.

the oil was changed in 2000 and the color is the same reddish I don't remember if the shop has changed the filter.

Mazootpusher · #15 07-17-2009, 08:47 PM

I would suspect the clutch k-1 and clutch k-2,
change the transmission fluid and filter,don't forget to drain the torque converter.
while the pan is out replace the k-1 an k-2 springs in the valve body.