Which speedo gear?

[Beetlejuice]

I did the math to figure out which vss gear I needed, but I'm not so sure its right. I'm guessing that I have a 19 t stock. I came up with 17.38. Is this right, and if it is should I round up or down? Seems like a drastic change for adding an inch or so of rubber. My stock tires were 235/70/16 and my BFG's are 265/75/R16. My truck is a '97 F-150 4x4 4.6 R407W 3.55. Axle H9. It also has a nasty shudder @ 40mph. and shakes violently at stoplights. Thanks, Jody

Register today or sign-in to remove these ads!

[MitchF150]

You are basically doing what I did. The only diff is I have the 5.4 and the 4r100 tranny. I do have the 3.55 gears and went from a 235/70/16 to a 265/75/16 tire.

My stock VSS gear was a 20 tooth. I replaced it with a 19 tooth. Before, I was losing 1/10 mile every two miles traveled. Now it's 1/10 every eight miles. About as close as I'm going to get, unless I get an even taller tire and switch to an 18 tooth gear.

I'd be only guessing, but I'd say you only need the 19 tooth one. Pull the stock one out first and count the teeth. Mine was black in color. The 19 tooth one was tan.