Weird shifting tranny
 

Hey yall, quick question about my 97 f-250 4x4 5.4. I bought it with a 3" lift and a set of 35" buckshots. I dont know what gear are in it because i did no work besides replace the bologna skin tires. Well my concern is how bad does being lifted and having 35's affect the shifting pattern. Its an auto and 99% of the time it doesnt know what gear it wants to be in. Cruising on the highway im fine or maintaining any speed it does great. If i slow down to maneuver around some dumb ass driver then try to accellerate again it hits 2 or 3 different gears like its confused.

You'll need to recalibrate the speedometer to read right with the bigger tires if that hasn't been done already. The PCM (trucks computer) is confused because it doesn't know how fast you're really going.

I have close to the same proplem with my 35 even with my 33, but I have a hypertech on it and made the corrections to the speedometer but does that also correct everything for the transmission also, ie does the trans piggy back off the odometer or what the odometer uses?

First, on the '97 you have to physically change the VSS gear to correct the speedo/odo. It is a good chance you have 3.73 gears, look on the tag on the rear end to know for sure. It isn't really a matter of the comp. not knowing how fast you are going, its that your effective gear ratio is lowered so much that the truck is no longer in the power curve, as it would have been with stock tires. Figure you are probably 15-20% off on the speedo/odo. A set of at least 4.10 gears will get you a lot closer to the power curve, might even want to go to 4.56's.

I have a 3.55 and love the 1800 rpm at 70 on the highway. plus the top end speed. but this problem has come and gone and come again over a two year period so it doesn't happen regularly. It gives me the feeling that it may be some kind of sensing that is working and then getting a bad connect some times. I don't know for sure?