Topic: Fj60 Locker/gearing change...

[sollostrongbow]

 Newbie here!! Have fj60 84', 5.7 LS1, NV4500 tranny. Currently running 5.29 gear on 33's. First question, 4.11 0r 4.56 gear because rig is wound tight at 65mph. If I go 4.56 lets say, do i need new lockers??

[Snowtoy]

Need to start with what the cruising speed of the LS1 is supposed to be, guessing it is somewhere between 1700-2200 at 70mph, then match the tire size you want/plan to run with your rpm cruising speed to determine the axle gear ratios.  This Engine speed/gear Calculator should give you an idea of what the different diff gear and tire size will have on the engine speed in each transmission gear.

If you want a more accurate rpm, use the measurement of the tires as they sit now on your rig, most manufacturers stated sidewall tire size is 1-2" shorter when mounted, which usually results in the rpms being 200 lower on the highway than the calculator indicated.