Couple different problems here I think.

1. Don't seem to be getting into the turbo on acceleration from dead stop.

2. Then, the shift through the first two gears is smooth as silk. However, when shifting into fourth, it just kinds "slides" through the shift. Sometimes it feels like it just "falls" into the next gear. Fully depress the accelerator after going into fourth and it's a dog. No acceleration whatsoever. Then when it downshifts back into first, there is a heavy "clunk". The clunk wasn't there before we changed the modulator valve.

Have replaced the modulator valve on the transmission, as well as the shift actuator(?) that goes in behind it (reminds me of a syringe). Fluid and filter also changed.

Am wondering if there is a kickdown switch on the 83 300D Turbo? If not what part controls the downshift from fourth to third when slowing and gives a boost to the acceleration?

As usual, any insights certainly appreciated.

__________________
Don
'85 500SL (Euro) - 186,000 w/a complete restoration and engine rebuild at 154,000
'95 C280 - 174,000

You should typically feel the turbo spooling up around 2200rpm's. I believe there's a kickdown switch under the accelerator pedal. Hard downshifts are typically caused by low vacuum.

__________________
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

As is so often the case, I have no solid answers to questions asked here, but do have some insight. My 83 300D shifted hard when I bought it. Replaced the modulator (it leaked) and found that most of the remedy was in adjusting the pressure control valve (I think that's what it is called). Suddenly my kickdown switch worked (and my cruise control now sort of works). Neither worked at all until I adjusted the control valve (not the modulator)

__________________
John Schroader
bio burnin' 83 300D, '83 300 SD, '79 240D
"I've never met a man who was good at making excuses who was good at anything else" Ben Franklin
"You cannot permanently help a man by doing for him what he could and should do for himself" Abraham Lincoln

Also check the hard lines to the banjo bolt, turbo switchover valve, and ALDA.

I had a hard line get snapped, and a rubber connector on the switchover valve split.

__________________
RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

99 W210 E300 Turbo Diesel, chipped, DPF/Converter Delete. Still needs EGR Delete, 232K

90 Dodge D250 5.9 Cummins/5 speed. 400K

Gone and still missed...1982 w123 300D, 1991 w124 300D

John Schroader : can you please provide details? Where is the control valve?