F250 help

[Dupontdon24]

Any mechanics in here, help needed. I have a 1999 f250 super duty 4x4.. New engine was put in last yr, not even 500 miles on it yet. I got the truck home and the transmission started acting up. It was acting like a shift kit was installed just punching into gear. So took it to local shop, replaced trans, replaced rear speed sensor, front left speed sensor, and it was determined the abs control module was bad, the abs light had been on forever. Found a abs module locally at a junkyard, it matched and the truck ran good from the time i got it from the shop to home. Now its shifting ratical again, feels like breaks are grabbing. We hooked it up to scanner and its reading the truck is moving while its parked. Anyone experience anything like this and have a heads up which direction to go. Its at the shop now, and i believe there going to tell me the used abs control module is bad, and the new one is 800 from ford. Thanks for any sight yall may have on this.

[SB09]

Funny as this sounds check your alternator... I've seen something similar one other time which I spent $1600 on for new ABS module and some other sensors. Truck still acted like you state. Turned out my alternator was acting up causing all the other electronics and the ECM to think something was wrong. I replaced the alternator, never had a single other problem out of it. This was on a 96 or 97 250. I can't really remember. Here's the problem with checking the alternator. It would act up sometimes, but not always. Took Ford leaving it hooked up and running most of the day to find the problem.

[archtaan]

Your transmission is shifting hard because it has gone into limp mode. It dramatically increases line pressure to protect the trans. Check and replace the rear speed sensor that is in the rear axle. They are notorious for going bad. Also there is a sensor on the side of the transmission that tends to fail.

I am going to guess the abs sensor from the junkyard is bad. Id bite the bullet and get a new one from Ford or check an online retailer like Rock auto. Id head over to the Ford truck enthusiast site or something like that.

[Dupontdon24]

Originally Posted by archtaan

Your transmission is shifting hard because it has gone into limp mode. It dramatically increases line pressure to protect the trans. Check and replace the rear speed sensor that is in the rear axle. They are notorious for going bad. Also there is a sensor on the side of the transmission that tends to fail.

I am going to guess the abs sensor from the junkyard is bad. Id bite the bullet and get a new one from Ford or check an online retailer like Rock auto. Id head over to the Ford truck enthusiast site or something like that.

Thanks for the replies. i replaced the rear speed sensor before I took it to the shop, then the left front sensor. The abs light went out after installing the used one. Its funny, truck setting still idling, the scanner is saying the truck is moving. I checked all over the ford enthusiast site, and pretty much the same thing. I'll mention the alternator when he calls me back to tell me the abs module is bad. The truck ran great for 2 days, been playing hell for the past yr, first the engine, which they had for 6 fricken months to get engine right, now this with the tranny.