In my 92 4x4 k1500 my speedometer goes straight to 90 mph after I let off the brake, and it will constantly jump while i'm driving. The rpm guage also rarely has a slight jump to it, and the gas guage is off by about ½ a tank. But I hove NO REAR BRAKE SYSTEM in this truck, period...NONE. I've been trying to figure out this speedo issue since January and have had no luck. Anybody know anything about this or had any luck fixing similar problems?