I have an 82' 300TD with transmission issues. So far, this is what I have done:
1. Checked the vacuum lines. Everything is fine (had to plug the one running to the climate control, to be worked on later).
2. Disconnected the kickdown switch under the accelerator pedal.
3. Adjusted the modulator valve

Everything was running adequately (don't want to say well), shifting properly, though sometimes hard and sometimes with a little flare. However, there was an odd problem: it took almost exactly 1.5 miles before the car would shift into second, then it would shift normally. Oddly enough, this had nothing to do with the amount of time the car was running. If I was stuck in traffic, caught all the lights, fiddled around in the car after starting it, etc., the car would still wait about 1.5 miles before shifting into second. I don't think it has anything to do with warming the car up, since it's 100+ degrees here.

Now it will not shift out of first at all. I tried to shift manually, but that does not work either. In L, S or D, I am in first gear. Yes, reverse works fine, and I can shift through the gears easily.

A friend suggested a stuck valve, but did not elaborate.

Any suggestions? I really need some help here, as my husband is making those "you really should get a reliable car" noises again. Soon he will move on to "I told you so", and I can't have that.


DeLoris

"Manually" upshifting is not what it seems. All that it does is permit automatic upshifting.

Make sure the fluid level is good, or better, do a replacement, with filter. Check Vacuum Control Valve, you'll need a mity-vac, or something similar. Then adjust the Bowden cable if so equipped. I think the stuck valve you mentioned is an internal thing. Good luck.

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83 SD

84 CD

Spent the day trying to troubleshoot this without much success. Fluid level is fine, vacuum is perfect, Bowden cable does nothing, good or bad (I even disconnected it without any changes). So, I have two more questions for y'all:

1. Is the governor the same as the modulator valve? If not, where is the governor? [If you could send a photo or a link to one, that would be ever so helpful.]

2. Assuming that the governor isn't stuck, I'm going to drop a new transmission in this car. I already have a donor vehicle, so finding a a good transmission is not a problem. Does anyone have any recommendations/warnings? Is there anything that should be done to the donor transmission (other than a thorough inspection and cleaning)?

DeLoris

The trans gets its signal to shift via vacuum and throttle position.

Sounds like it has a vacuum problem if it was shifting (reasonably) well before.

Any other vacuum problems? Do doors lock. Do they stay locked? Anything recent work where something might have gotten knocked off?

Mileage on trans?

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Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)

Some people have had success with TransX. It's probably worth a shot.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

The trans gets 2 signals. One from the modulator which is throttle position. The other is the governor which is road speed. If the governor is stuck the trans will not see any road speed and not upshift. It will think it isnt moving.
I dont have a pic of where the governor is but it's on the rear most part of the trans on the right side I think. It is probably stuck with grit from worn clutches and thrust washers. Pull this valve out and clean it. I'lll bet the trans will shift just fine.

There was some vacuum problem, but it was being slowly but surely fixed. The doors do hold a lock. I can even lock and unlock them many times in the morning.

There's about 240K miles on the trans.

I'm going to try looking at the governor and will report back.

Vacuum, or lack thereof, is not your problem.

........one from the Bowden cable which is throttle position............


The modulator will only "modulate" the speed of the shift.........not the point where it occurs.