Good Morning, I have a 1988 740 GLE sedan with the 4 cylinder (non Turbo). At 70 mph the tach is showing about 4200 RPM. The OD SOLENOID IS FUNCTIONING PROPERLY AT ALL TIMES. . I drove my mechanic's personal 740 wagon that had the same powertrain and his RPM was much lower at 70 (maybe 2750) than what my 740 indicated. He thinks my tach is broken So does 4200 RPM at 70 MPH appear too high and what part would I likely replace? BTW, my gas mileage is about 22 mpg on the highway at 70 mph. I read that some 740 (non turbo) owners are getting middle upper 20's on the highway, and as much as 28 MPG. Hmmm! Thanks guys, this is my first post and I don't even know where to look for your responses. have a great 4th of July weekend Mark B

 

While I don't know anything about your particular car, the RPMs sound too high. I suspect your OD is not working. If you have a good transmission shop in the area it might be worth a visit...

 

your overdrive isnt working. you should be in the mid 2k's at 70 mph