I am very familiar with the problem of ABS and Brake lights on, and speedo not working below 30 (or so) MPH. I had this problem before. A quick replacement of the rear diff. sensor and all is good.

My problem is a little different this time. I got in my truck this morning, started it up, and drove down the drive way. My brake pedal normally starts to tighten up about half way down. The pedal went to the floor this morning and then both idiot lights came on. The truck will stop ok, but I have to push the pedal all the way to the floor before it stiffens up. I bled the brakes, replacing a lot of the old fluid, and I still have the problem. The speedo works just fine at all speeds in forward and reverse.

Could this still be the rear diff sensor? The idiot lights would lead you to believe so, but the brakes operate differently, and the speedo works 100%.

-Robert

 

I almost forgot...it is a 1998 Ram 1500 4x4. 97k miles.

 

sounds like a maste cylinder problem. if your not loosing any brake fluid, then your master cylinder is most likely bad.