My 1989 K2500 4-wheel drive: Looking for the rear axle ratio as well as transmission gear ratios so I can figure out what highway advantage I'd have going to a 5-speed (overdrive) transmission, like 1990 has.

I did have a gear vendor overdrive in my 1985 GMC diesel, which was well worth the money as RPM at 65 MPH was 2,100 RPM.

Appreciate the help.

Randal

 

I've always liked the 3.73 gear ratio. 3.42 was too high and 4.10 too low for me. I've got the 3.73 in my 1998 K-1500 with the 5 speed overdrive and like it quite well.