I hope I am not breaking any protocl by starting a new thread, but I have read everything I can find but still have not been able to fix my no 4th gear problem, I have nearly run out of options. The car is a US Federal version 1985 300D turbo. It has 260,000, I have had it for 18 months. 18 months ago I changed the transmission oil and filter. The car has always had a delay when putting it from Park to Reverse and from Reverse to Drive. A few months ago the motor would not turn off, I found I was leaking vacuum in both the door lock system and the AC system, so I plugged those vent lines. to mess with later This solved my shut off problem. I tested all vacuum lines forward of the firewall and everything holds vacuum except the vacuum amplifier which feeds the EGR. I eliminated the vacuum amplifier, so it and the EGR are removed from the vacuum system. While testing, I found that the VCV was leaking, so I adjusted it so that it has approx 12-15 psi at idel and drops to about 0 at full throttle. I also adjusted the Bowden cable. With all these adjustements, the car's transmission shifts better than it ever did before except for 4th gear. With these adjustements, it goes into gear from Park to Reverse faster and from Reverse to Drive faster, but it still will not go into 4th gear. Before this problem, I would often have to press the gas and let up for it to shift properly at highway speeds. I read a post where a 300d would not go into 4th gear because the overdrive pedal behind the gas pedal was stuck, so I checked it and unplugged it for a test drive with no success. I've checked the transmission fluid level and it is fine. I've tested everything I can find, excep possibly changind the transmission filter again; although, as I stated it is only 18 months old. Aside from that I am out of options. I appeal to the MB gurus, in your opinion is it a bad transmission or can you think of any other tests or checks? Does anyone know of a reputable MB repair shop in Augusta, GA? Thanks for any advise you can offer.

The kickdown switch is what activates a solenoid in the tranny. It is possible that the solenoid is stuck.

Also check your shifter and selector bushings. It is possible that the tranny is not really in "D" but in "S".

Also the bowden cable maybe a tad too tight. It is what controls the shift points according to throttle position.

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RRGrassi


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

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

91 W124 300D Turbo replaced, Pressure W/G actuator installed. 210K

90 Dodge D250 5.9 Cummins/5 speed. 400K

You have covered all your bases well.

I don't believe that any adjustments that you can make will magically return 4th gear.

You can attempt to put some additional slack in the Bowden cable to reduce throttle pressure...........but.........this is not solving the problem.........it's just masking it by making the shifts earlier.

It's probably transmission time.........whether a valve body will cure it........or the clutch paks are toast........is the real question.