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New to the Forum and new to the Powerstroke world. So I bought a 99 e350 School bus with the 7.3L. I bought the Bus In Prescott Az, drove it home 93 miles with no transmission issues but did have a check engine light. Truck sat for 2 days, upon restart/drive it started shifting all the way to 4th gear then Lock-up by 15-20mph and would not go over 36-37mph almost like a fail safe. I got a hold of a scanner, got a few codes and replaced what was bad. The exhaust back pressure sensor, injection pressure sensor, and did the shift solenoid(ford sensor). It runs far better now, no codes. The PCM is commanding the extremely early/fast shifts. I have narrowed it down to the transmission shifting issue being after a key cycle. The batteries are shut off everytime I park it due to a power drain (sticker on the dash to turn off battery switch). So when I drive it again it shifts fine but If I pull over, shut it off, and restart it then the shifting issue starts again. Shifts 1-4 and into lock-up by 20mph lugging the engine. It will then not go over 37mph unless I finesse the throttle with very light input, then it sometimes will downshift and accelerate beyond 37. Any more than 1/4 throttle though it will go back into a failsafe kind of mode, with a little more finesse you can get it to go again. Sorry for lengthy post, just wanted to cover all I know. Any input is appreciated as I am stuck. Thanks
 

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New to the Forum and new to the Powerstroke world. So I bought a 99 e350 School bus with the 7.3L. I bought the Bus In Prescott Az, drove it home 93 miles with no transmission issues but did have a check engine light. Truck sat for 2 days, upon restart/drive it started shifting all the way to 4th gear then Lock-up by 15-20mph and would not go over 36-37mph almost like a fail safe. I got a hold of a scanner, got a few codes and replaced what was bad. The exhaust back pressure sensor, injection pressure sensor, and did the shift solenoid(ford sensor). It runs far better now, no codes. The PCM is commanding the extremely early/fast shifts. I have narrowed it down to the transmission shifting issue being after a key cycle. The batteries are shut off everytime I park it due to a power drain (sticker on the dash to turn off battery switch). So when I drive it again it shifts fine but If I pull over, shut it off, and restart it then the shifting issue starts again. Shifts 1-4 and into lock-up by 20mph lugging the engine. It will then not go over 37mph unless I finesse the throttle with very light input, then it sometimes will downshift and accelerate beyond 37. Any more than 1/4 throttle though it will go back into a failsafe kind of mode, with a little more finesse you can get it to go again. Sorry for lengthy post, just wanted to cover all I know. Any input is appreciated as I am stuck. Thanks
I don't know about the bus but they learn how to shift based on how you drive is my understanding. So, it has to relearn it's shift strategy every time it loses power. I've noticed a slight difference if I disconnect the battery but only slight. Maybe a hydra php tuner will help? Best $300 I spent on my truck

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Discussion Starter #3
I don't know about the bus but they learn how to shift based on how you drive is my understanding. So, it has to relearn it's shift strategy every time it loses power. I've noticed a slight difference if I disconnect the battery but only slight. Maybe a hydra php tuner will help? Best $300 I spent on my truck

Sent from my SM-N960U using Tapatalk
Thank you for the reply. Mine goes from shifting very well to skipping all the way to lock-up overdrive in a few seconds. It does A member on another forum had said he has seen the same problem before and it was the 4x4 L circuit in the pcm being grounded or broken. He said even though it's not 4x4 there is still a circuit in the pcm. Not sure if it's the answer but definitely going to investigate. It does shift just like it would be in low range judging by the commands on the scanner. As far as the tuner goes I will be looking for one as soon as I figure this issue out. I will def give that one a look as the bus def needs a little more power haha. I appreciate you reaching out!
 
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