Hi all. I've owned this 123 for nearly a year. When I first got it in the cold weather, she would slip between second and third when it was car was cold. Once it warmed up, no flare whatsoever.
All through the summer months, she never slipped at all. But now that the cold mornings are starting to set in again (sub 50 degree nights) she is slipping again. And on two occasions this fall, I seem to have lost the transmission altogether. What has happened is it has slipped between second and third, but rather than take my foot off the gas as I normally would to let it slip into third, I have stayed on the gas for a brief moment. On those occasions, I have had to pull over to the shoulder and put it back in Park, then drive and start out again, and everything seems OK.

With this much info, would anyone care to give me a diagnosis. Fluid is always at the correct mark, but don't know much else about this transmission.
Thanks

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1981 300TD
1985 300TD

What car and transmission are you talking about?

Have you changed the oil & filter in the last 30,000 miles? If not, do so.

My money is on a 1981 300TD. I will even go 2:1 odds.

A 2-3 flare can frequently be cured with a new K1 accumulator spring. Slipping is another story. Slipping occurs while in a particular gear; flaring occurs between gears. Are you slipping and flaring, or just flaring?

81 TD it is.
Thanks for the clarification between slip and flare. I have read a lot of forum discussion and never quite sure about the difference.

This has definitely been a flare. Always between gears, and if I just back off a little it shifts into gear. I was a little concerned about the two episodes where I was unable to get it to shift, but will ignore them for now.

Would a k1 spring issue resolve with a warm transmission?

Thanks. I plan to do a fluid and filter soon. According to PO it had been done in past year before I acquired, but....

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1981 300TD
1985 300TD

In my experience, yes.

The 1981 300TD has a 722.118 transmission, which doesn't have an easy exchangeable K1 spring. The transmission is controlled by vacuum-only, if there is a problem with the transmission, first the vacuum control system needs to be checked.

Not according to my information, which indicates that a 722.315 transmission is applicable. (I am assuming a US delivery vehicle, in the absence of information to the contrary.)

For transmissions in general, a common cause is a hard shrunken o ring / boot / seal on the filter where it seals to the valve body.

This area is typically above the fluid line and will draw air.

I believe the transmission is a 722.303.

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1981 300TD
1985 300TD

Then my recommendation stands. Install the improved K1 accumulator spring train. (This assumes that the remaining shifts are not problematic.)