buck45
New member
93 5.0 E4OD; I'm having shifting problems; for example, starting out with light to moderate throttle, when it shifts into 3rd it will buck, shudder, and start to bog down. If I start out with more aggressive throttle it shifts fine. Also, cruising along in 3rd gear, a light to moderate throttle increase at around 30-35mph and under 1500 RPMs causes bucking and shuddering. It just seems to upshift too early and then it starts to bog down, buck and shudder. It also does the same thing when trying to downshift out of 4th gear, but at higher speeds (45 mph and less than 1500RPMs). It seems that the shifting problem occurs mostly under slight to moderate throttle when the RPMs are at the low end (1500 or less). When the RPMs are low I've found that if 1) if I press the accelerator pedal aggressively or 2) if I pump the pedal just slightly (quarter inch) a couple of times, it shifts fine. I've read that E4OD shifting is based on signals from the TPS and VSS. However, today I read that the PSOM signal is also used by the E4OD. So here's my question. I was running 31x10.50s but now I'm running 32x11.50's. My PSOM is set to 9.18 (for 31's), however to calculate the true speed with 32's it should be set to 8.87. Because of the larger tires I know that the actual speed now is higher than the speedometer indicates, and I know it seems far fetched, but does anyone know if the shifting problem could be caused by the wrong calibration constant setting in the PSOM?
