Vehicle: 1998 Dodge Ram 1/2 Ton 4x4 - 5.2L 318

About a week ago both my ABS and Brake lights came on, but I haven't really noticed a change in my brakes and my fluid is topped off.

Yesterday, I noticed my speedometer jumping around. For example, if I'm trying to go 55 MPH it will jump from 50-60 MPH. This also caused me not to be able to use my Cruise because it would accelerate and brake with the jumping.

Today I went out and purchased and replaced the speed sensor on the tranny (recommended by the shop assistant) - not the problem.

I then did some research and went out and purchased and replaced the ABS sensor. I reset my computer and noticed both lights were off and the speedometer was working normal. After about 15 minutes of driving, the lights kicked back on and the speedometer started jumping again but this time it was only jumping around 1-2 MPH difference. The only reason I really noticed it was because I was testing the cruise control.

What could be the issue?

 

Check the connector at the sensor for the abs on the rear diff. It hangs out in a rather obnoxious spot, and gets dirty/corroded, thus, the signal isn't exactly "clean".