Finally got the abandoned Merc running.

It appears the trans keeps slipping out of 4th above 45mph and top speed is about 45-50 ish in 3rd. I can accelerate to almost 60 then it suddenly kicks down to 3rd and the car slows to about 45-50. If I let off the gas the trans shifts back to 4th but if I try to accelerate again it just keeps down shifting back to 3rd.

At first I assumed low fluid but it appears to be at the correct level. Did a filter trans change and had a very hard time getting the fluid level correct. It measured about a CM low on the dipstick, I added 1/2 quart and now it reads way high. I assume the distance between the two marks represents 1 qt or 1 liter. Is this not so?

Anyway, the old filter was marked/scratched 2/98. The filter change made no difference.

I then disconnected the wire from the switch under the gas pedal, which I believe is the kick down switch. Now I can maintain about 65mph but will still down shift if I completely floor the pedal.

I'm thinking possibly a vacuum problem. Should I disconnect and plug all vacuum lines to the trans and see what happens? Or will this cause damage?

BTW, the cruise control seems to work fine but the door locks are kinda "sticky". Both are vacuum systems.

__________________
1987 300TDT
1981 VW MKI Caddy 1.6 diesel, waiting on engine swap
1983 D-50 Power Ram 4x4 "Mitsubishi" 2.3 turbo diesel
assorted gas powered crap and motorcycles

RIP: 1984 300TDT, 1982 300TDT, 1984 190D 2.2, 1992 300D 2.5, 1987 300TDT, 1982 Maxima LD28, 1983 Maxima LD28, Isuzu C223 P'ups X3, 1983 Holiday Rambler 6.2 Banks turbo diesel, 1984 Winnebago LeSharo 2.1 TD, 1985 Allegro 6.5

Added some Trans X maybe that will clear it up after a few miles.

I've checked and rechecked the fluid level and it is correct.

I re-attached the wires to the kickdown switch and the transmission goes right back to downshifting to 3rd in the 50mph range and the car won't go any faster. I let up the gas pedal and it upshifts to 4th and if I try to ease down on the pedal to go faster again it keeps downshifting back to 3rd.

Unplug the kickdown switch wires and the car will drive about 60-65mph and only downshifts to 3rd if I floor the pedal.

The vacuum pump is working, perhaps a vacuum line is clogged?

I'm going to try looking for tthis m odulator thing. The Haynes manual says nothing of it.

__________________
1987 300TDT
1981 VW MKI Caddy 1.6 diesel, waiting on engine swap
1983 D-50 Power Ram 4x4 "Mitsubishi" 2.3 turbo diesel
assorted gas powered crap and motorcycles

RIP: 1984 300TDT, 1982 300TDT, 1984 190D 2.2, 1992 300D 2.5, 1987 300TDT, 1982 Maxima LD28, 1983 Maxima LD28, Isuzu C223 P'ups X3, 1983 Holiday Rambler 6.2 Banks turbo diesel, 1984 Winnebago LeSharo 2.1 TD, 1985 Allegro 6.5