OD Speedometer: Was Re: tr6 overdrive

["John & Allison Cyganowski" <janah@att.net>]

<snip>

After swapping the guts out, it turns out it must have come from an non O/D
car and it was reading about 20 miles off. ( I didn't realize the gear ratio
in the speedo's were different)  So I ended up taking the gear keeper off
the used one and put it in mine and now everything works as it should.

<snip>

Okay, this sounds familliar.  What happens to your odometer in this 
situation?
When you say 20 mph off do you mean +20 or -20?

Is there a way to tell an OD speedometer from a non-OD speedometer?

John Cyg.