Just got this truck (89, F150, 5 speed overdrive). In all the gears it has a pretty rough vibration at 2000 rpm. It's very narrow, and can be accelerated through (but it's right at 65 mph in 5th). Based on feel alone, I'd probably tend to shift a little later (2500 or so), but that vibe is forcing me to shift earlier. The owner's manual lists speeds to shift at, but they seem REALLY low. Is this a known issue, or should I be looking for causes. Any neat tricks to move it up to about 3000 or so?
Also, I can't find a factory manual for it (am in the process of tracking down a "Chilton's book of lies" to use until I can find a real manual). The AC cycles about every 8 seconds in defrost. I'm guessing that's normal/intended? I can feel it in the cab, and notice it if I'm driving real slow (out of driveway in first). Guessing I shouldn't feel the surge? Idle is a little rough, and seems slow (500 or so on dash tach, haven't measured accurately or looked under hood for correct number)
Thanks,
Bob