Hypertech 3400 Speedometer Calibrator (Review and Final thoughts)

[Texas_Ram]

I just put 35's on my truck and I purchased a rough country speedo calibrator.

Before I did the calibration, I checked the speedo with my phone GPS and it is dead on.... I called the tire shop and they said they didn't calibrate it. Has anyone had one automatically calibrate? is this even possible?

If you were looking at your phone GPS while the phone is plugged into the usb of truck at the time, then your phone gps is copying your speedometer. Unplug phone then look at gps speed compared to speedometer.
I went from 32” to 34” tire and speedometer was off by 5MPH at 60. Off fewer at lower speeds.

 

[CigarXO]

Just my 2 cents... and a little hope - w/o reading all the thread:

I bought my 2020 Ram Limited EcoDiesel in Dec. Waited until Mar21 for the BDS airshock 3.5" lift and Fuel Maverick Black/Chrome wheels to arrive. Paired with Toyo Open Country A/T 35x12.5/22s to replace the OEM special rims and tires. After install, speedo was off by -4mph at 60-70mph. Asked the shop to flash Speedo. They did and gave me a Hypertech 3400. Their flash resulted in +4mph, so tonight I grappled with the Hypertech Speedo Calibrator. I'd used a similar tool on my Jeep 5.9er and 06 GMC Denali so was experienced with the lack of instructions, warnings of pulling fuses and poor reviews. I'd also heard some flash kits disarmed the Parking Sensors. Well - rest at ease - I did not pull fuses. I too experienced the "stuck in Reading VIN" mode before I used the white plug. I plugged the small white connector into the canbus (sp) behind the parking brake selector, plugged in the OBD plug and followed the initiation instructions. I only changed the tire size and left all else stock. I used the actual height of my tire which is 33.625 (rounded to 33.75 - darn TOYO - where's the other 1.25 inches of tire?). The programmer prompts you to cycle the truck a few times and you are done. I road tested vs WAZE and speedo is right on. (I was motivated to get my fuel economy corrected. The EcoDiesel is providing ~20mpg)