I have a 1990 Dodge Ram Wagon B150 with a 5.2 L V8 engine, and automatic transmission. The speedometer needle is accurate up until about 25-35 mph, then starts jumping around and then may stop for awhile, but is usually registered my speed at 10 mph less than it actually is. The speedometer only jumps when I am accelerating. It USUALLY doesn't jump when I am braking or coasting. If anyone can tell me what they think needs to be done to fix this I'd really appreciate it!! this is a REALLY annoying problem!!!! Oh, and when it's cold outside (below freezing) the needle will sometimes just fall down to zero but usually only sits there for a few seconds, and then starts jumping around again..

 

Yours should be a cable type system instead of electronic. I would remove the speedometer cable (first disconnect the cable housing from the tranny and pull the cable out) and then clean off the old grease and apply new grease to the cable and reinsert it back into the cable housing and reconnect it back to the transmission. This generally solves 90 percent or so of these type of problems.

 

thanks i'm going to give it a try right now! I appreciate the help!!

 

Sorry to contradict, but considering that the needle will sometimes drop to zero, I think the problem is going to be with the speedo assembly itself. A sticking cable will cause the needle to jump around, but it will not allow the needle to drop to zero or cause a 10mph loss in the reading.

 

These speedos can be had used for $10, so if lubing your cable doesn't solve the problem I'd recommend a trip to the boneyard for a good used one.