Bricknose Mechanical Speedo question

[tnthielen]

Hey Guys,

I've got my truck back on the road and the speedo was off by about 5, when I'm reading 35, I'm actually doing 40-41. When I'm at highway speed, I'm off by about 10, so at 65, I'm running 75. Now that I've got the lift kit on and I'm running 35's, my speedo is off by about 15 at highway speeds. I'm reading 65 and really doing 78-79 according to my GPS. According to this link:

http://www.lmctruck.com/icatalog/fd/full.aspx?Page=123

Which speedo gear do I need? The gear that I have currently has 19 teeth (I counted it out 3 times). So do I go up or down with the number of teeth and how many? My guess would be a 2 tooth jump to either 21 or 17...

I have 3.55s and a ZF-5, so I'm assuming that the 4 speed manual selection (bottom half of that section) should work?

I'm getting ready for a big road trip towing our camper on Friday about 2000 miles, so once I get another minor electrical gremlin taken care of, I'll post a bunch of pics of my conversion to include **** pics of that Moose Mover 7.0 I got from Mel...

Thanks!

-Todd

 

[crash-harris]

Do a google search for "ford speedo gear calculator", or just speedo gear calculator. Then order gears from here or ebay. http://www.transmissioncenter.org/Ford_Speedometer_Gears.htm

IIRC, 3.55's with 35" tires is like a 20 tooth (or maybe 18 tooth?). I'm running running 4.10's and 37's in Bruiser and I think my driven gear for the speedo is red, aka 21 tooth.

 

[catbird7]

My truck has 4.10's, with 35" tires and speedo is off approximately 7mph (slow) when compared to GPS. Replaced speedo gear in transfer case several years ago and I think it was yellow???