85 300D won't downshift at Highway speed unless I back off the gas pedal..

[Carrameow]

My 85 300D won't downshift at Highway speed unless I back off the gas (well, actually Diesel) pedal.

The tach climbs to 4000 rpm as I hit the 45 to 50 mph range, even if I floor it. If I let up on the accelerator pedal, or back off on it, I get the downshift, which seems to be smooth and well modulated.

In troubleshooting, I always check the last thing I touched. I recently pulled the IP to retime the engine and I disconnected a lot of linkages and hoses. I may have bent some linkages unwittingly. One question I have is why the tach won't climb higher if I floor it. For some reason I think there is more RPM available bu the travel in the linkage may be misadjusted so when I floor it, I can't get full travel at the IP.

The other point is the car sat idle for three months while I repainted it. During that time i would only take it around the block once a week to keep everything "moving". but I rarely went over 20mph.