83 300CD can’t go into 4th gear.

[Dalton2091]

I have a 1983 300CD. Probably somewhere around 320000 miles. It’s acting very strange where the car will only attempt to shift into 4th once on a cold start and it’s rare that she will actually shift. The car will flare into I get back down to 2nd gear and then won’t try again until she sits and cools off. Once in the past month, I got her to 65 with 4100 rpm’s and shifted to S then back to D and she shifted into 4th. If I kept the throttle a little bit past maintaining 65 , she would climb higher in speed but if I gave it too much gas she would slip.

The vacuum modulator holds vacuum and she shifts very nicely , no jerking but you can feel it. She shifts from 2nd to 3rd at 20mph each time. I unplugged the kick down switch to see if that would help and it did not. I’ve been trying to read the transmission fluid level and I keep getting very different results. Yesterday I drove her for 30 minutes , parked on level ground , cleaned off the dipstick put it all the way back in and it read at the max line. Then today I checked it after the engine got to 90c and it read below the minimum line , then I drove for about 10 minutes and now it’s reading way past the max line. I guess you can’t double dip and get good results. I don’t really know. The engine was running in all these tests.

I’m totally confused as to what could cause the engine to only search for fourth once and never again.

Your help is greatly appreciated. Probably going to do a fluid exchange tomorrow and see if that does anything. Only had the car a month , the fluid doesn’t look burnt. No idea how much is actually in there tho.