wildly bouncing 355 speedometer ???

I have a '96 355 Spider with a manual 6 speed. My speedometer has just started to wildly bounce around at speeds below about 40 mph. It doesn't go to zero at a stop either. It stays stuck at about 10 mph. From 40 to 45 mph and up, its dead steady like it should be. What's gong wrong? My understanding is its electronic. Is there a sending unit going bad? Where is located?

 

If its like any other Ferrari speedo it never did go to zero because there is a pin stopping it.....

Intermittent could be sender but could also be dodgy connection at sender (not sure of exact location on 355 but a quick search should reveal previous similar threads - maybe gearbox)

 

My F355 did this. It would fluctuate up and down going up to 180km/h while sitting at the traffic lights. It was the sender unit which is located down the side of the gearbox. Check the connectors first but once I replaced sender unit there were no more problems.

 

I've looked at the parts diagrams and can't find the sending unit. I am told its on the side of the gearbox. Which side and exactly where? What parts diagram shows this? Its not with the speedometer and I can't find anything looking at the transaxle diagrams. Doing a search under speedometer sending unit brings up nothing. ????????????????

 

Pretty sure it is #34:

Ferrari F355 M5.2 (1996+) Parts : Table 31 - GEARBOX COVERS AND LUBRICATION

 

Thanks Watson. I looked at that table but a "pulse sensor" just didn't register. I'll double check the connection first to be sure that's not the problem before buying a new one.