GMT-900 - Problem Tuning Larger Tire Size?
01-04-2010, 06:08 PM
#1
GMT-900 - Problem Tuning Larger Tire Size?
Guy that works in the building behind me has recently installed a lift and 325 60 20" with factory 3.73 gearing on his GMT-900 Silverado.
I've read a few threads reporting issues with the BCM, TCM/PCM and programming larger sizes. Are these issues still a problem when using EFI live?
As a test i updated the sizes on EFI-live and reflashed my truck and had no issues, granted I'm still running the factory sized 20" tires. Took a drive varied speed, hard to notice if the speed-o was reading correctly as the roads are covered in snow and ice and there is not much traffic to compare to. I'd like to be sure it will work prior to him purchasing a license.
I've read a few threads reporting issues with the BCM, TCM/PCM and programming larger sizes. Are these issues still a problem when using EFI live?
As a test i updated the sizes on EFI-live and reflashed my truck and had no issues, granted I'm still running the factory sized 20" tires. Took a drive varied speed, hard to notice if the speed-o was reading correctly as the roads are covered in snow and ice and there is not much traffic to compare to. I'd like to be sure it will work prior to him purchasing a license.
01-04-2010, 06:23 PM
#2
The problem lied at High speeds. IIRC after you change gears or tire sizes the ABS pulse rate in the BCM ended up being slightly off the PCM/TCM's calculations at higher speeds.
On mine, at about 80+mph the Parking brake light comes on.
Didn't cause the speedo to be WRONG or anything. Just made it think something was messed up.
On mine, at about 80+mph the Parking brake light comes on.
Didn't cause the speedo to be WRONG or anything. Just made it think something was messed up.
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