I have a stock 1987 F150 with a 5.0 EFI and an AOD tranny.

Well, my speedo is slow by 3 mph or so. When I am going 52 according to the speedo, I am evidently going 55 according to my friends car. When I get down slower like 10-35 it's accurate. What's wrong? Factory error maybe?
As far as I know, everything is stock and should be stock. Tire height should be stock, rear gears are definitely stock, everything.

Whether or not this is a factory error, what speedo gear selections can I get to correct this?

Thanks!

 

No one knows?

 

Factory speedo's are +/- 3%. So yours is acceptable or your "buddies" could be off. Ever think of that?



Chris


p.s. Radar guns are +/- 3% too.... thats why most cops will pull you over when your 10mph over.

pps Have you owned the truck since brand new???

 

Thanks for the reply. I haven't owned the truck since it was new. My grandfather owned this truck one year after it was new until he sold it to me.

My friends car and fathers truck both indicate that it is off. And most of the time (when people are actually going the speed limit) I stay with the flow of traffic. So, I am guessing that when my speedo says 52 I am going 55 or at least pretty close. It is pretty much accurate from 35 and lower also.