Not sure if this should go here or in the tuning section.

But a buddy of mine has a 2006 Silverado 1500. He had the transfer case replaced because of service 4wd was on. After that he installed 35" tires and 4.10 gears. I changed his tune for the 35s and 4.10s. Now at speeds above 45mph his service brake system light comes on. No DTC's.

Took it back to the shop and they replaced a wheel speed sensor. The tech said that all of the wheel speed sensors were reading the same mph. But that mph is 10mph less that GPS and the speedo says. I have verified his speedo with GPS and it is with 1 or 2 mph.

What could cause all of the wheel speed sensors to read the same but 10 mph less than the speedo?

 

Calculated tire size is wrong, 35.00 with 4.10's should be 34.93.

That could be the issue.

 

Thanks I didn't even notice that.