How are others with a Gear Vendor OD calibrating their speedo?

I have a '96, A4 (TH400) with a gear vendor OD and I'm having wacky speedo issues. First off, I started with a M6 tune to delete the transmission controls so I wouldn't get SES transmission codes. With the Gear Vendors OD unit they also suggested I use their speedo calibration unit as well which is mounted to the OD unit and has the speedo wires connected directly, so the PCM does not control the speedo function anymore. Gear Vendor tech guy is stumped and escalated it to the engineering dept. Now their engineer is having me test amps on all the wiring and wants me to believe it's a wiring issue. Could be, but I highly doubt it as I've wired according to their specs and had their tech guy walk me thru rewiring it a few different ways. At idle, the speedo registers 60MPH and then as the car drives, the speedo flucuates up and down, and then when I really get into the throttle, the speedo falls flat (0 MPH). Gear Vendor OD works, transmission works... everything mechanically is sound... it's just the speedo isn't calibrated correctly.

I read the sticky posts on calibrating the speedo by splicing the VSS wires into the front ABS sensor and adjusting tire size and rear gear ratio thru the PCM tune to get the speedo to function properly. Just wondering to hear from some others that have a Gear Vendor unit and what they did to calibrate their speedo. Thanks

 

Turns out Gear Vendor is overnighting a new one of their speedo modules. They think the voltage was a little low from a reading I gave them. We'll see....

 

Love it when guys never give the fix to their problems!