I just purchased a 1991 f-250 lariet truck I noticed the speedometer is off at 80 mph on meter I am actually going 68 mph I have checked the tires are the size required for the truck and the rear end is 4.10 like it states on the door. So my question is what else might be throwing it off and how do i fix it.
Thank You for any advice on my problem Jae

 

It is possible that someone fitted the wrong speedo drive gear on the cable at the trans/transfer case end. You will probably have to change that gear.

 

Thanks for responding Lazy K were would I found out what the correct drive gears is so I can check to see if what I have is right or wrong?

 

https://www.ford-trucks.com/forums/1...eter-gear.html Have a read through this thread for info.
As everything is stock (as far as you know) you could just get one from a dealer or online from partsguyed.com