Speedometer

I have a 2001 Chevy Express 3500. My speedometer is acting a little crazy It doesn't go up or down in a smooth manner. When I am slowing down it will stop at a higher speed and then drop 10 mph or so until it catches up. It acts the same way during acceleration.
A friend of mine said that some of the vans don't have a speedometer cable but have a sending unit on the transmission.
Any help would be appreciated.

Thanks

If the speedometer hand is sticking sounds like the cluster or speedometer head.
Have it tested on a scanner first.
Dealer may be able to check it or get a rebuilt one.

I would be curious if you found a solution to your problem. I have a similar problem with a 1993 g20 van; although I have watched my speedometer go to 85mph while sitting at a stop light. Since we have had a problem with the DRAC speed sensor once before (0 mph when driving down the road at ~30 mph in first gear; I just love computer controlled transmissions), my mechanic says the problem this time is the speedometer although I am not totally convince that the computer is not sending out a strange signal.