What gears are you running in the back? What size tires are in the back? If any of these are different than factory stock, you will need to get a speedo ratio adapter. In your case it looks like the speedo is reading about 13% faster than what the truck is traveling at, assuming your garmin is correct. If so, you need a 13% speed up adapter. Call Jim at PATC Transmissions 888-877-1008.

I was running about 21% off. They sold me a 20% speed up adapter for $70. Now it reads close enough to dead on.

BTW-If you have a smart phone, there are a couple real nice speedometer app's. Much easier to use with bigger readouts, etc. I use Speed Box.



Craig

My '50 Chevy 3100 5 window, '62-235cu, 3:55 rear
My truck ....... Respect The Rust
If I'm not working on my truck, '65 m00stang or VW camper, I'm fishing with the wife or smoking Salmon.