My 84 300d runs great but doesnt shift properly. The main problem is down shifting. When the accelerator is floored the trans stays in high gear (3rd or 4th depending). If I change gears with the selector everything works normally. Also it seems like it doesnt hold the gears long enough and I end up in 4th way too soon.

Things I have checked so far:

Vacuum: All lines are good and routed to the correct places. I replaced all the soft rubber pieces I could see and checked all the plastic lines with my mity vac.

IP "full load" linkage: Adjusted to be fully open when accelerator is pushed to WOT

ALDA: Removed and cleaned both banjo fittings, adjusted the screw which still had the original cap on it. Turned 3/4 turn CCW.This seemed to soften shifts and increase power, but caused slipping from a dead stop after the trans is hot, unless "L" is selected on the shifter. Turned it back 1/4 and seems to be ok but have not road tested extensively.

So my hunch is one or all of the vacuum modulators are inop. Do they go bad often? Is the ALDA modulator normally open.. meaning when voltage is sent to the modulator should it close or open? This one is open with no power. I havent tapped power into it to see if it closes. What sends the voltage signal to the modulator? Is there a control unit? What sensors control this signal?

Thanks in advance!

chec the switch under you accelarator pedal.it can be stuck or just no good.....chec wire for kic down is plugged in bac of tranny,,single wire on pass side rear of tranny.

Shifting time it controlled by the bowden cable. It can be adjusted. It's connected to the linkages on the valve cover. Try adjusting that to get the RPM shift points higher.

As suggested you kickdown switch could be bad. You can unplug it and see what happens, you can also force the trans to downshift by clicking the switch with the pedal. When the pedal is all the way on the floor you can click the switch, which should cause the trans to downshift. If you get nothing then the switch is bad.

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Is the switch under the accelerator the only kick down control?

Any ideas why it wants to be in 4th gear no matter how fast the car is going?

I def do not get any downshift when the switch is pressed. Where does the switch send voltage? Is there a fuse for that circuit?

Button under "Resources" Tab,Marked ADVANCED SEARCH.

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'84 300SD sold
124.128

The actual kickdown solenoid is on the pass. side of the trans [on a 123].
A single wire is attached to it.
If you have voltage at that wire then the solenoid may be bad.

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1981 240D 143k 4 spd manual -SOLD

2004 VW Jetta TDI 5 speed 300k -still driven daily

If the switch ends up being bad shoot me a PM, I bought two on accident and can't use them (EPC listed the wrong one for my 91, and the "optional with" part ended up being another whole button )

-Jason

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

Sounds good thanks! I need to get underneath and check out that solenoid,

I adjusted that trans control cable, now it shifts a lot better! Still not perfect though. Sometimes it gets stuck in between gears when shifting but as soon as i reduce throttle it drops right in. Also still has intermittent hard shifts. mainly 1-2

But WAY better than before! Thanks a lot!!!

I'd look at the blue flying saucer transducer now. I just found mine was the cause of too hard 1-2 shifts.