I have posted this before...but it might be worth repeating...
The problem with HP Tuners is that there is at least one parameter that they do not adjust right in the PCM Files that must be changed when setting the speedo on the dash. When you do a "Read Entire" they capture all the adjustment parameters and store them in their files (or write them back when you do an update), but then they don't actually bring all of them to a Graphical User Interface (GUI) adjustable 'knob' in their software (or they don't include it in their final adjustments).
For 4.10 gears you can work around the problem by playing with tire size parameters because there is enough "adjustment" left from 3.73. With 4.56 gears the change is to drastic and the "correct" parameter needs to be changed...
When I changed my SSR from 3.73 to 4.56 I went through the excercise of collecting data (at least 10 log files) and sending it to [email protected]
to get to the bottom of this.
Ultimately, I sent my SSR PCM and TCM (My truck is an Automatic) to Bryan Herter at PCM4Less in PA. He uses LS2 Edit to make the changes (per an email from him). The speedo was dead on after he made the change.
Before I sent the PCM/TCM to PCM4Less, I did a "Read Entire" with HP Tuners. When I got my PCM and TCM back I did another "Read Entire" with HP Tuners. I then copied over the changes from the PCM4Less Tune to the Tune I saved before I sent the PCM/TCM to PCM4Less, and saved it as another file. So at that point I should have had identical tunes. (The compare function in HP Tuners showed they were identical)
Then I uploaded the copied one (created with HP Tuners) to the SSR. The speedo was wrong, just as before the PCM/TCM was sent out. I then re-loaded the PCM4Less tune. The speedo was dead on per GPS. This simple test shows that HP Tuners is missing something in the background.
I sent both files to [email protected]
He confirmed they were missing some parameter that is saved in the tune files, but not adjusted with their GUI.
He later assured me that it would be fixed in later versions. However, in the latest beta (Version 2.23) that I have recieved (about 2 mos ago), it has still not been fixed. I went through the speedo issue with them in Dec 2007.
You can make adjustments in HP Tuners such that the logged values in HP Tuners scanner, or the values shown on an Aeroforce Gauge or Dashhawk match GPS Exactly and are dead on. But the Speedo won't match the ODB-II/CAN port scan/log data. It is the value that affects the Speedo on the dash that HP Tuners does not correctly update. HP Tuners is not the only software with this issue for the affected vehicles. Super Chips, and Diablo MicroTuners are also known to have the same problem.