4L80e and diff ratio change
After all the time I spent to get better transmission control of a 4L80e after switching from 4.10s to 3.42s it now appears the PCM needs to be reflashed for the newer gearset ratio so transmission control is corrected to the ratio change. One programmer says hacking VSSB does fix speedo but it does not re-calibrate ABS or transmission control for ratio change. There seems to be an ABS re-calibration requirement for larger dia tires too.
GM Upfitters manuals show that year 1999 3.42 gearsets were an option on all GM C/K chassis configurations. However, transmission and engine oil coolers are required for all C/K series w/3.42 gearsets.
I'd like some feed back on this.
99 GMC SUB, 2500, 4x4, 6.5 TD (F) #H32 enhanced blk, Phaser timing set, B&D IC, 3" ATS exh, K&N w/prefilter, 4WD NVG 246, 4L80E kevlar Transgo off road/tow mods/B&M supercooler, 14 FF MagTec w/locker 3.42:1, 9.25" IFS frt/diff 3.42:1 w/ARB locker, AutoMeter Boost & pre-turbo pyro meter, 12,000 lb hydro winch, Warn classic bumper w/brushguard & diesel scoop, Max E-torq Stage 3, hi pop inj, oil bypass sys, on board air comp for front ARB locker & tire inflation, DynaView driving/auto-cornering lts, DZ nerfs, A/T 285/75/16 SilentArmor 3750 lb rated on 3750 lb rated Alcoa, 3 IP drivers 2 r spares.