Mud in my Veins
Join Date: Oct 1999
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Re: 96 F250 transmission question
Well your first line of defense is to pull the stored trouble codes out of the computer and see what the tranny says it detects. I have the same tranny and I've learned that it's a very fragile and complex beast, so diagnosis is quite different than most trannies. It might also be worth finding a tranny shop that will hook into it and see if your computer is screwy or what particular facet of the tranny is foul. The speedometer problem might give us some insight though. When you say it goes out, do you mean the needle drops to zero or does the odometer blank out as well? The speed sensor is easy to spot, it's on top of the rear axle and has 2 wires coming off it. They then go to the 4WABS computer, then to the PSOM(instrument cluster) where it gets calibrated to tire size, then to the PCM that controls tranny shifts. If you lose power to the PSOM, the tranny goes into a crazy safety mode and will shift HARD and wont shift at the correct times, and it definitely wont get to OD. I know there is a common problem with a loose ground somewhere behind the instrument cluster, and if you have this problem then it might be intermittantly killing power to the PSOM, which of course will make the tranny go nuts.