97 3500 Brake/ABS Problems
 

I have a 97 3500 Cummins auto.It is stock, my problem is that when I start it up both he ABS light and brake light come on and stay on. I have used a hand held code scanner and even had a shop with a snap-on scanner check it with no luck. Any ideas? Also the truck has now top end power, fuel pressure good. Would just light to pull my car and trailer about 80 mph, right now it's lucky to do 60.

abs and brake light are prob from the abs sensor on the rear dif.. the truck is a 3500 so it has 410 gears in it unless someone changed them out. so its probly screaming going to the highway at 70 what size tires are you running on the truck?