3.42 Ratio Effect on MPG
How much does the 3.42 affect MPGs?
It appears to actually improve high speed MPG from my experience. I can understand where it might reduce MPG at steady state slow speed such as 55 MPH where the engine isn't working very hard.
I have a 96 Tahoe with the optional trailer ratio (3.73 at that time) and it got almost 1 MPG
better at 75 mph than my son's 96 with standard 3.42 ratio.
My 2001 Tahoe also has the trailer ratio (4.10 at that time) and gets about the same MPG as my neighbor's 2003 at freeway speed.
My assumption is that at higher speeds, less power enrichment is needed with the trailer ratio due to less load on the engine.
I should also mention that I have about 100k miles on my 96 and over 250k miles on my 2001 and transmissions in both trucks have never had anything more than oil changes done to them! Possibly the reduced load on the transmission allows it to live longer?