Changing the ring and pinion going to create drama?

[72timemachine]

My friend has a 2006 Chevrolet 1500, 2wd with the 4.3 engine mated to a stock manual transmission. He wants to install a higher gear ratio with limited slip.

He had the original ring and pinion fail a while back and kept the old parts. Not sure if we figured it out correctly but I believe his original numbers from off the ring gear calculated to 3:23. He tells me the truck loaded with his tools is a real dog off the line but is great on the freeway.

The question is, if he replaces his ring and pinion to let's say a 3:73, will the ecm recognize this change and start storing trouble codes? Will the odometer need to be re-calibrated?

Thank you for any help.