For anyone building a 2019+ Ram trying to calibrate the Speedo and not finding many easy options since the ODB port is locked with new security nonsense.... I got you...
Thanks to my studying at YouTube University, i found a way to dial in the Speedo 100% accurately in 2 minutes with no bypass module needed.
Eddies Life on YouTube did a video for his 2019 using a Hypertech Speedo calibrator for a Jeep.
I tried the Hypertech unit for my Tundra and it failed miserably so i was skeptical.
But... Since not many options for the 2019+ Rams and Eddie having a good reputation, i tried it.
Hypertech Part # 752504 (for a Jeep JL).
Small white plug, plugs into the board (NOT the ODB) near the parking brake, turn truck on (DONT START) and follow the prompts. (plug circled in red)
NOTE: The ram doesnt have any 12v HOT USB plugs, they are all ignition hot, so i used a battery pack shown below.
Tires measure 41" in my level driveway. After some trial and error, setting it to 39.5" on the calibrator had my speedo spot on accurate verified with 2 different GPS units.
Having the proper speed is great, but it also put the tranny shift points back to where they need to be and the truck drives amazing right now.