Last year I had a thread going concerning (my own) used w123 240d transmission I swapped into my 1980 300td. The tranny had worked great in my 240d, but it had sat for about four years before it went into the TD.

The original trans was a vacuum-only unit, as was the one from the 1983 240d. If I recall correctly now, the original was a .118, the 'new' one is I believe a .117.

Long story short, once we got it into the wagon, it wouldn't shift into second. It would wind up in first and stay in gear (at least up to my tolerance point in terms of RPMs) unless you backed off the pedal... at which point it would slip into nothing. It would 'catch' into first again if you slowed down almost to a stop.

I changed the vacuum pump diaphragm to bring the vacuum up to proper levels. No change. I installed a new crossover valve on the valve cover (the white three-way valve). No change. I tried draining and refilling the fluid, and playing with the vaccuum modulator adjustment. Also completely disconnected the kickdown switch. No change at all.

I tried driving it for short hops though the summer, still no change. In the fall as a last resort I poured a bottle of SeaFoam into the trans, drove it a little, then parked it for the winter.

No change this spring. Other things had my attention all year, so the car only got back onto my radar last week. However, one thing did change: the car had been stored at my mechanic's lot, where I only had limited scope to drive it (stuck in 1st) due to traffic. Last week I towed it home, where I am able to drive it further at a time without fear of police attention.

Today I pulled the dipstick and realized that it was still way over full, from the SeaFoam. I slapped my head for having left it overfull all this time, and drained about 1.5 quarts -- then drove the car again.

NOW I HAVE SECOND, but nothing more.

First holds very, very high, until just about the single dot on the speedo (so nearly 25 mph). I've tried to get it just about to the two dots, but no signs of upshift beyond second.

What do I do now? Remember, this is a vacuum-only-control transmission. No Bowden cable, no throttle position lever.

I am inclined to add a little fluid (I overdrained a bit) and try adjusting the modulator....

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22