I purchased my 69 last year and while the previous owner said everything worked, I have found this to be less than true. The fuel gauge is definitely off (I have another thread going on this). I also think the speedometer is inaccurate. Neither of these things were something I noticed when test driving it.

The speedometer seems to be showing about 10mph too low when I'm going about 65. I haven't tested this for sure yet with someone pacing me but I will when spring comes. I don't want to risk having the police tell me I was doing 85 when I thought I was doing 75 either. With my luck they won't believe me that the speedometer is off.

A new 350 engine was put in just before I purchased it and he said the transmission was redone but original. I also noticed that the front and rear tires are different sizes. Fronts are P215/65R15 and the rears are P245/60R15. I'm not sure if this is typical or not based on the books I have read. I don't know if any of this makes a difference but thought it may be relavant to include.

This is probably way beyond my skill set to troubleshoot but are there any ideas (beyond the gauge being bad) on where I should start to look if I do find that the speedometer is really inaccurate?

 

I just replaced my speedo cable which was remarkably easy. You might simply reach under your dash to make sure the connection of the cable to the back of your speedometer is tight. Then follow it down to the transmission to double check it's nice and tight. That's an easy thing to do and never hurts.

JV

 

If you have a gps you can use that to check your speed. Those are as accurate as you can get. The speedo being off is probably due to gear changes, tire/wheel changes. There are several sites that help you with this. here is one: Speedometer Gear, Speedometer Gears, Ford, GM, Dodge 700R4