I test drove a very nice 1983 300 turbo diesel the other day. I really liked the car but am quite leary because the transmission shifts so hard it will jerk your neck back or chirp the tires going around a corner. It shifts hard through all gears, not just one or two. Any suggestions? Because if this can be fixed for a reasonable price, I think I'll buy it. Thanks

The modulator valve on the transmission controls the firmness of the shift. The modulator is vacum controled. The vacum controls on the diesel engines are located on the valve cover and on the injection pump. The less vacum the modulator valve has going to it the firmer the shifts are, so it sounds like the car might have a vacum leak in that system.
I would have it looked into pending the purchase of the car, usually it is not an expensive repair to correct a vacum leak in that system. What you don't want to find is that someone adjusted the modulator valve to cover up a slipping/dragging shift problem due to wear in the transmission.
Hope this helps,


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MB Medic
14 year MB tech
7 year shop foreman @ independent MB/Volvo shop

Does this same system apply to gas engined cars like my 190e?
My car has about 70k on it, and shifts really hard, especially when cold. The 1-2 shift is always neck-snapping, and will cause wheelspin around turns. The 2-3 shift is harsh, but the 3-4 shift is barely perceptible. All shifts improve when the tranny is really hot, but they're still not great. Is there an adjustment I can make, or should I take it to someone who's done this before? Thanks.
Jason