My 1990 Ford F-150 has developed a shift problem. It is a 4x4 Lariat model, 168,000 miles on the original 351 Windsor engine. It has EFI, and an E4OD transmission. I had the transmission rebuilt by a known transmission “specialist” here in town last year, as it was doing hard upshifts and also doing delayed upshifts. Seven months after the rebuild it started “hunting” for a gear around 30mph; going from second to third to second quickly. The transmission guys troubleshot the truck, had it for ten days, and finally installed a second E4OD transmission. The problem didn’t go away. So they decided it was a bad PCM computer. A few days ago, I had the PCM replaced with a “refurbished” one from an outfit in Philadelphia. The PCM numbers all matched. But the problem still exists; it goes from 2nd to 3rd and back to 2nd ten times in five seconds. So if I’m going 30mph (the most common city speed limit here in Spokane, WA) I am forced to put the shift lever in “2”, and use more gas. I’ve spent over $2600.00 trying to get this problem fixed. The only thing left seems to be the wiring harness between the PCM and the transmission? And if so, where do I get a 26 year old working (or an NOS) wiring harness? Or could it be something else? Thanks in advance.
Had an 03 f150, never a problem, but my suggestion would be to look at vacuum hoses.
Since the vehicle is fuel injected, and has an electronic 4 speed overdrive transmission, it means there’s a vehicle speed sensor.
If this sensor has failed, it could be confusing the computer where the shift points are.
Are you certain that the problem is in the2/3 shift? It could be that the lockup clutch is not engaging properly. Was the torque converter replaced when the transmission was overhauled? Is there any ‘chuggle’ when pulling away from a stop? Or possibly a chatter that sounds like it’s coming from the rear axle at low speed?
Thanks for that tip. I’ll ask my mechanic if he can replace that ASAP.
Yes, it’s jumping from 2nd to 3rd, anywhere from 28-33mph. Yes, teh torque converter was replaced. No “chuggle” or chatter sounds. With two rebuilt transmissions and two different PCMs, it’s hard to think that either of those things are causing this problem. It does shift into second sooner than before, upon casual acceleration… I’m wondering if the speed sensor is the problem… News at eleven.
I agree. But wouldn’t that cause “shift confusion” with all the gear shifts, not just 2nd to 3rd? And I would think that Louie’s (the trans rebuild folks) would have thought of this speed sensor as a cause…maybe not.
@manderson99217 - If it is determined that you need a wiring harness use google and look for Painless Wiring harness. There are others but the custom auto builders seem to prefer Painless.
In my perusal of the responses, I don’t see any mention of the Throttle Position Sensor. The TPS sends the opposing signal to the VSS i.e. as the TPS voltage goes up the PCM will delay the upshift. If the TPS signal should jump to a high value, the PCM will force a down shift. So have the mechanic verify the calibration of the TPS and the smoothness of the transition from throttle closed to wide open throttle. Alternately, you might just have the TPS replaced and reset to specification