i just got my tranny rebuilt a week ago with triple disc, new valve body, seals, deep pan, and sensors all cleaned up and mine still takes a while to shift at WOT from 3rd to 4th, so im not sure if its just these tranny's or maybe the throttle position sensor, but my TPS was replaced not to long ago...so i dont what it could be im kind of wondering the same thing...
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97' 2500,12V,AT,4x4,230K MILES, DUNRITE TRIPLE DISC & V/B, BILSTEIN 5100's, DSS STABILZER, DIPRICOL GAUGES, BHAF, BOOST ELBOW, #0 FUEL PLATE, KDP KILLED, T/C LOCKUP SWITCH, 15* TIMING, 2" LEVELING KIT, 4" TURBO BACK TO 5" MITRES