here is my setup, for those who forgot..;-)

Engine 5.3 LMG 1GKFC130X7R239150 2007 Yukon 5.3 2wd
ECM 3GNEC12047G152683 2007 Avalanche 2wd
12605897 YNAU service number 12597121 86ynauk16194d88a

Tranny 4L60E 1GNFK16367R390210 2007 Suburban 5.3 4wd
TCM 3GNEC12047G152683 2007 Suburban 2wd
TCM cal/OS :OS 24235341 cal 24234634

I am still running the 2wd tunes in E38 and T42, 'cause my 2007 TCCM setup isn't ready yet.

Last week I had a GPS unit installed and checked my speedo. It showed that the speedo was about 3,5% off for the distance and 9% off ( cluster values or too low..) for the speed ( I have a 2007 cluster installed...!) . That's strange 'cause I calibrated the speedo in T42 and E38 according to the tire spec ( 285/75/16).

So I checked the difference and adjusted the speedo settings ( rev / mile) in TC42/ E38.
Next day I checked it with the GPS unit.... and I got the same readings: 3,5% / 9% off. I adjusted the same amount again and did another test: Guess what: still the same error as in the very beginning. It looks like the T42 is ignoring my changes. There is no full flash necessary for speedo cal changes ???

Harald

Any ideas?