Military Vehicle Repair: gear ratio on 85 m1009 blazer, vacuum modulator, rear axles

Question
i recently came across an 85 military blazer w/6.2l non-turbo diesel & turbo 400 transmission. it seems to really rev out over 50mph. is there a straight-forward way to change the gear ratio to allow for highway speeds, or is this destined for off-roading & plowing?

Answer
Hi Donald,'
First make sure it is shifting to hi. A bad vacuum modulator won't let it shift.
Also, if the shift linkage is incorrectly adjusted.
And last, make sure the transfer case is actually in Hi.
I have several of the trucks, and have had a few of the Blazers. The ambulance type truck is extremely power geared, but I never found one of the Blazers to be. They usually cruise pretty normally.

To change the gear ratios is no different than any Chevy. You do need to change both front and rear axles gears.

Van