Truck Doesnt Like Going Into Overdrive

HDdave · April 10, 2007

Well my truck has done this as long as I remember. I can sometimes get it to shift to overdrive if I'm going downhill and I'm very light on the pedal. Just yesterday I was on the interstate and I had it go into overdrive on the on ramp and I was able to cruise at 70mph and 2000 rpms for maybe a 1/4 mile then on a slight downgrade it shifted into 4th and stayed there the whole way home at 2500 rpms. I don't remember if it was like that with the 245's that came stock too, or if just putting on the 285's fooled the computer or something..... My other theory is that there is a valve in the tranny that is sticking. I plan on getting the tranny flushed out and having new synthetic fluid put in, but I dont know if that will fix the problem. It bothers me for 2 reasons- mpg's!, and my truck is a lot louder at 2500 than 2000, so it just makes for a slightly annoying riide for any of my passengers.

Also, when I get around 62 or 63 on the speedo my service engine light will, start to flash, and the code reads multiple random cylinder misfire, but I cant feel the misfire at all. Another member had this problem and his ended up being a bad crankshaft speed sensor, so I'm assuming that is my problem also. I just wonder if they could be linked in any way...