so.. after months of freezing temps etc .. as in about 6 lol.. the speedo decides to work?
at least for a few seconds lol.. then after about 40mph and hit the brakes goes down to zero again lol ...
wtf is going on!!!??

 

These speedos are electronic and use several capacitors that fail intermittently and partially creating many various crazy combinations. You never know how these forces are going to combine and cause inexplicable symptoms.

 

I would also check the wires at the sender in the rear differential. They have a tendency to break over time and become intermittent.

 

just thought it was bizarre! it hasn't worked in a long long time. i was thinking it might be the sender as well. we have had wild fluctuations in the ambient
temperature lately around here. drove around today quite a bit and it still didn't work. i've been using an old small android phone for a speedo (and odometer!)
using the app DigiHUD as it doesn't need to be connected to the internet to operate....

 

My Speedo was intermittent for several years before I finally sent it in for rebuilding. You can send your instrument cluster and about $400 to various places and they will make everything work like new. I bit the bullet and did that and do not regret it.