No Upshift to 3rd or 4th gear 81 240D
 

Well I just got through installing a rebuit engine in a friends 81 240D and the engine is running fine after some tweaking on the timing. I just took it for a test drive and it shifts fine from 1st to 2nd but that it where it stops. I have checked the vacuum line to the trans and the modulator and all seem to be fine. Vacuum from the main brake booster line is reading 25 on my vacuum gage so I know it is getting the suction it needs. Anybody have any idea what the problem could be. I am well versed at the engine rebuilding and all the other parts of these cars but the Tranny stumps me because of the lack if knowledge.

MBJOE

MB Joe,
Glad to see a fellow north carolinian... I know this is silly but did you check the tranny fluid? If thats not it, sounds as though you may have a stuck valve!
good luck

Does the 240D have an electrical kickdown switch under the accelerator pedal? Could it be shorted somehow - wires pinched?

Just throwing out ideas........

Ken300D

Check that the vacuum drops off as the rpm increase. I have almost the same problem with an 82 SD, looks like I am missing a restrictor and the vacuum never drops below 14". Try plugging the line going to the modulator and see what happens.

The important vacuum to watch is that which goes to the modulator. The line on 240Ds is teed into right at the group on the valve cover. Follow the line up from the trans.

Basically it needs to be high at idle and proportionately reduced by throttle movement untill gone at full throttle. For an indepth discussion of these systems see the article I wrote. There are a lot of variations but the concepts of control are discussed:
http://www.continentalimports.com/ser_ic20242.html

Steve and all of you thanks for the replys. I have been checking everthing I have read on your site Steve and and still have not got it to shift right. When this lady brought this car to me to fix all the things broken the reverse did not work. From another recomendation I found the bolt above the kinkdown switch backed out just about completely. I tighten it down to about 5 threads and locked it down with the locknut. Does this bolt control more than just the reverse band, if it does maybe this is the problem. Thanks again for all the replys and yes the fluid is at the right level.

MBJOE

Well just a progress report. I have checked all the vacuum lines, the modulator and the vacuum valve on the injector pump. Does anyone know the correct adjustments for the modulator. Can you start from a zero point and adjust it to factoru specs. I know it was going into 3rd and 4th before I pulled the engine so what could have happened or come loose to cause this no shift problem.

MBJOE

The way that vacuum causes no shift is by not being there at the modulator. You need to use the gauge hose set up in the article (or reasonable facsimile). You need to tee it at the modulator (hard way) or at the first junction the hose ends at near the valve cover (easy way - same vacuum).

For test purposes try hooking the source line straight to that line giving full vacuum all the time. The car should shifts bing, bing, bing and probably slip all over the place. If this is the case vacuum somewhere inbetween is the answer. If you are good, lucky, and tenacious the article will have you adjusting it sweet.

Well Steve thanks for the great advise. I hooked up the the trans straight to the Booster line , took it out for a test drive and it shifted to 3rd and to 4th. I have hooked up these vacuum lines by the MB manual that I have so I really can't figure out which connection is wrong. More testing tommorow but thanks again for the tip .I will go back now and re-read your continental article for the final adjustments.

MBJOE