Where is the speedometer cable connected in my 87' F150, 4X2, V6, Man. Trans? Front or Rear axle?

When I bought the truck, it had 31 X 10.5 x 15 tires on it, which threw the speedo off by 5mph. I calculated this by both timing & distance & calculating the diameter of the tires compared to the o.e. tires.

The front left tire went flat & the right front was bad, so I changed them out to the o.e. tires - leaving the larger tires in the back.

I'm still getting the 5mph diff - so I assume the speedo is connected to the rear axle?

 

The speedo is connected to the tailshaft of the transmission and is operated by a cable. You will have to change the gear on the end of the speedometer cable to correct for the larger tires.

 

Thanks for the info.

I assume it's near the pumpkin?

Where do I get the different gear from? What size?

 

The tailshaft is not near the pumpkin. It's the tailshaft of the trans.

 

The gears can be found at any Ford dealer. There is an electronic speed sensor for the abs on the rear end 'pumpkin' but it is not what drives the speedometer. The speedometer drive comes from the transmission, not the back of the truck.

http://www.fordracingparts.com/download/charts/129.pdf

there's a calculation you can make at the bottom of this linked page that might help you figure it out. You have to know the number of revolutions per mile of the tires, and you have to know the number of teeth on the drive gear inside the transmission. I'm guessing it's gonna be 8 tooth, but I'll emphasize that being just a guess.

 

It's right by the fuel pump that on the frame rail. Its on the drivers side of the transmission before the drive shaft. About a 1/4 thick and its black. I pulled my cable out by mistake when i changed my external fuel pump, I think it comes right out, mine did.