Old Girl (aka Project Underhaulin)

[nlped]

If it’s a 3.73, you’d probably be okay with the 30” tire, but it may hunt OD (shift back & forth between 3rd & OD) at lower speeds (40-60 mph). My ‘87 did that terribly on all these backroads up here, so I went to a 28” tire and all was “cured”.

You know you can just jack the rear of the truck up, put it in neutral, mark a spot on the pinion & a spot on one of the rear tires and just spin the tire and count the revolutions of the tire vs the pinion and you’ve got the gear ratio. 2-3/4=2.73, 3’ish=3.08, 3-1/4=3.27, 3-1/2=3.42, 3-3/4=3.73. You get the picture.