Offroad Trailblazers and Envoys

4.56 gears and ABS

G80, GU6, GT4, GT5, WTF? This section is for gearing and driveline stuff.

by AzEric » Fri Jun 28, 2019 12:14 pm

My 2004 truck originally had 3.73 gears, and when I toasted the transmission oil pump and had to rebuild I decided to swap to 4.56 gears to match my 33 in Yoko MTs while it was down. I was well aware of the fact that this might cause issues with the ABS system from reading around this and other forms about the swap (i.e. https://gmtnation.com/forums/threads/ab ... wap.14024/) but I am possibly going to go to 35s in the future, and didn't want to have to do gears more than once. I am simply posting this as an update from most of the other articles, dated back in 2015. During gear break in on my truck, the ABS/brake codes set as expected. I used the sps system to update the software on all of the computers in the vehicle to the most current rev, and then used a Tech II to update my tire size to 285/75R16 LT. That's it. ABS issue has not returned. Going to verify the speedo with GPS today, but cruising in traffic I was reading about correctly if you consider most people drive ~5 over around here.

Cheers!
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by Trail X » Wed Jul 03, 2019 11:01 am

I'm not sure I follow Eric. I've had this issue for years now, and I just unplug my abs fuse to keep the dumb alert from scaring the hell out of me every time I drive. What is the sps system you refer to? I can't imagine updating tire size would fix the ABS issue entirely, because it would not take into account the new ratio of rear ABS sensor to front ABS sensor due to the gear change. Can you explain further?
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