1996 Cable Speedo Bouncing and Inaccurate

I have a 1996 3.4L 4x4 MT. Below 50 mph, when it's above 35 degrees or so outside, the speedo reads approximately accurate. Above 50 mph, it'll fluctuate between 50 and 60 or so. When it's cold, it'll fluctuate between 20 and whatever speed I'm actually going.

Where should I start troubleshooting? I searched, but if there's a thread that addresses my problems, please direct me to it.

 

I would start with lubing the cable or replacing it. On motorcycles I have had a bit of lube in the cable has solved most speedo issues.

 

I assume my best bet is to pull the gauge cluster and dribble some oil down the tube?

 

Nope pull the cable lube the entire thing put it back in.

 

Perfect, thank you! I'll try it and report back.

 

You can disconnect at the tranny and pull out the cable put a quality grease in hand and put on cable as you work it back in.