1983 300SD transmission issues - PeachParts Mercedes-Benz Forum

turbozeke418 · #1 09-10-2012, 03:25 AM

I just purchased my 83 SD this week and it only has 131K. When stepping on the accelerator it takes a few seconds before she actually starts to move. My N/A 300TD takes off quicker to 20 mph. After 20 though this thing gets going.
It also seems to shift very soon into fourth gear. If I decide to manually shift her on hard throttle she shifts into 2nd well (chirps tires), when I shift her into 3rd she will just rev till I let off the accelerator a little and then bangs into gear. When I shift into 4th (D) its hit or miss when she wants to engage. When I floor it regularly sometimes it shifts into 1st in 2 seconds and sometimes not till around 40mph. The 3/4 shift is almost always within a second of each other. When shifting from drive to park it still sound like something is moving or slowing down internally before it park engages. 1-2 seconds.

Govert · #2 09-10-2012, 10:45 AM

Check the throttle linkage first, rubber parts can be deteriorated and the linkage may need to be greased. Check with the aid of an assistent.

turbozeke418 · #3 09-10-2012, 04:19 PM

I checked all of the linkages and lines going to the tranny and everything is OK. When someone presses on the accelerator the linkages go to the max point so everything is moving properly. Any chance its the Vacuum modulator? I've heard about issues with it before? I never had any issues with the TD and the trans so this is all new territory for me.

Secondaries · #4 09-10-2012, 06:21 PM

Sorry to repeat something that already has been said, but please double check your throttle linkage and your bowden cable.

Make sure the little round roller is at this position at rest:

And that your bowden cable is adjusted so that this little tab has a slight gap here:

FYI, in this picture I am moving the linkage so that all the slack is removed and any further I pull will move the pump throttle. With slack this gap will be a little bit bigger (which can be seen in the first photo).

When I got the car, that round bushing was halfway through that slot, and the transmission was shifting a bit later than it should. After making these adjustments, the car feels "correct".

Sorry if these pictures are too large, I am at work and have no software to resize!

turbozeke418 · #5 09-10-2012, 06:50 PM

The pics are AWESOME! Thank you. I will check that out later tonight after I get out of work. I love this huge pics. It only lets me load small ones. The larger pics are a plus!

kerry · #6 09-10-2012, 07:00 PM

I believe you have two issues going on. The timing of the shifts is controlled by the bowden cable. Adjusting it will adjust the timing of the shifts. The harshness of the shifts is controlled by vacuum. More vacuum, less harsh shifts. Sounds like your transmission is getting too little vacuum. You'll need to monitor the amount of vacuum going to the modulator as your drive around and shift using a Mity Vac or vacuum gauge
t'd into the modulator line, led out of the cowl and resting on the windshield so you can see the vacuum levels.

turbozeke418 · #7 09-11-2012, 01:23 AM

Quote:

Originally Posted by Secondaries

Sorry to repeat something that already has been said, but please double check your throttle linkage and your bowden cable.

Make sure the little round roller is at this position at rest:

And that your bowden cable is adjusted so that this little tab has a slight gap here:

FYI, in this picture I am moving the linkage so that all the slack is removed and any further I pull will move the pump throttle. With slack this gap will be a little bit bigger (which can be seen in the first photo).

When I got the car, that round bushing was halfway through that slot, and the transmission was shifting a bit later than it should. After making these adjustments, the car feels "correct".

I just checked my set up and there appears to be nothing wrong with it

turbozeke418 · #8 09-11-2012, 01:25 AM

Quote:

Originally Posted by kerry

I believe you have two issues going on. The timing of the shifts is controlled by the bowden cable. Adjusting it will adjust the timing of the shifts. The harshness of the shifts is controlled by vacuum. More vacuum, less harsh shifts. Sounds like your transmission is getting too little vacuum. You'll need to monitor the amount of vacuum going to the modulator as your drive around and shift using a Mity Vac or vacuum gauge
t'd into the modulator line, led out of the cowl and resting on the windshield so you can see the vacuum levels.

Kerry...How do I adjust the bowden cable? Should I lengthen or shorten it? Or is it just a trial and error type thing?

kerry · #9 09-11-2012, 07:12 AM

Quote:

Originally Posted by turbozeke418

Kerry...How do I adjust the bowden cable? Should I lengthen or shorten it? Or is it just a trial and error type thing?

There's a threaded portion with a nut where it terminates at the valve cover. I can't remember which way to change it to move the shifts in which direction? There are threads here.

toomany MBZ · #10 09-11-2012, 09:18 AM

To extend the time the gear stays before upshifting, ON MINE, loosen the white nut.

Video pending.

toomany MBZ · #11 09-11-2012, 10:25 AM

Bowden cable on MB transmission, 722.303 - YouTube

turbozeke418 · #12 09-11-2012, 01:10 PM

Quote:

Originally Posted by toomany MBZ

Bowden cable on MB transmission, 722.303 - YouTube

AWESOME!

TnBob · #13 09-11-2012, 02:13 PM

Common enough issue with such a great response this should be made a sticky !!

toomany MBZ · #14 09-11-2012, 02:14 PM

Thanks turbozeke, BTW, that's a 13 mm wrench.

I had to turn it in more, trial and error. It shifts from third to fourth at ~3800 rpm, so I'll back it out a bit more.

turbozeke418 · #15 09-11-2012, 03:22 PM

Quote:

Originally Posted by toomany MBZ

Thanks turbozeke, BTW, that's a 13 mm wrench.

I didn't do anything other than have a problem lol. My bowden cable adjusts very easily with just my fingers. I turned it all the way in and it shifts smoother and at lower rpms. I had to go to work so I just left it and when I get home I'll play with it a little more. I guess I'll eventually find that "sweet spot". Thanks again for helping me out in addressing the issue. Now on to the sluggish start. I'll continue that though in the other post.