My speedo is off!

Apologies in advance to anyone who opened this thread expecting nudie pix.

Vehicle: '93 Mazda B2200

Mileage: 294K

Recently I noticed that the speedometer is reading low, like 10-15mph under what my butt says actual speed is. Then I noticed that the needle drops below 0 when stopped. In the pic the truck is off, but same position when running & full stop.

The speedo is still functional, but the needle doesn't move at all until I reach 2nd gear speeds, so somewhere around 15mph it starts to nudge upwards, but starts at the below 0 zone. Once I am up to a butt-guestimate of 45mph, it's reading about 30mph. The sweep seems to be normal (meaning it's not jerky or irregular in it's movement), but since it's starting below the gauge marks it's no longer accurate. These gauges do not have a physical stopper preventing the needle from dropping below the marks like I have seen on some vehicles, at least not on the driver-facing side of the panel.

There have been no changes to wheels or suspension, no recent repairs to anything other than the carb (sticky choke plate, removed burr). I have not crawled under it yet to take a look at it due to soggy gravel driveway conditions. Any thoughts or recommendations on where to start troubleshooting? Thanks in advance!

I don't know if that has a speedo cable or if it's electronic, but if it's electronic the cluster would be my first suspect.

There are several apps for your smart phone that make good substitutes while you get it figured out.

The needle slipped.  Pull the cluster apart and reset the needle to 0, that should get you back to where you want to be.

In reply to Run_Away:

Pretty sure it's mechanical, the electronics on this thing are pretty basic. For example, the check engine light comes on every 20K and the fix (once I have verified that the engine is still present) is to unplug a connector and plug it into a twin receptacle dangling next to it. 

In replt to Stefan :

Dang, that sounds like work.  Once I get it apart do I just move the needle to 0 by hand or is there some clockworks in there that need to be "wound" in some fashion to get it back to the 0?

My 91 miata was that way.  I always wondered why I was passing eveyone like crazy until I got pulled over for 15 over when I know the Speedo only said 10 over.   Cop wouldn't busge on the ticket with that excuse.   Popped the needle off and reset based on GPS speed.   It was right on after that all the way through usable speed for a stock  91 miata

I guess it slipped too. Should be able to pull it straight off and push it back on in the correct position. Might slip again though, so maybe a dot of super glue?

Gotcha, pull it straight off. Sounds kinky but I'll try it.

If its cable driven, slip off and put back on at zero.  If its driven by a stepper motor, there is usually a stop built in to the motor, so you can put the needle on a bit high, and rotate it down to zero.

If the needle actually moved instead of an internal fault in the mechanism, I wouldn't be shocked if it were cracked where it slips onto the pin.