Building my Square body crew cab short bed 4x4

[SlugSlinger]

This math I use often to figure RPM at speed.
336 is a given to make the math work and this is with Zero converter slippage so basically a standard trans will get these numbers.
And do not go by advertised tire diameter you need to measure the diameter of the tire as it sits on the vehicle.

336 X MPH X Gear Ratio ÷ Tire diameter.

I checked my 3/4 ton 14 bolt and it has 4.10 or 4.11 ratio.
TH400 and I will add in 10% for converter slippage.

Math shows 2,895 RPM at 65 MPH with a 31" tire add about 280 rpm to that for a non lock up automatic.
33" tire puts the math at 2,720 RPM. at the same speed.
28" tire = 3,205 RPM.

My Jeep runs almost exactly 2,500 RPMs at 65 MPH. I have 5.38s and 35” marked tires. But most tires don’t measure what they are marked. The Jeep has the factory 4 speed with overdrive and lockup converter.

 

[Ar15]

great looking truck, quad cabs are scarce,

 

[AKguy1985]

Nice truck

 

[Camo]

You're tire diameter will determine what your gear ratio should be. The old 14 bolt corporate axle was a good choice if it's a 3/4 ton but gear ratios are limited versus a Dana axle but if you don't get too "INSANE" on tire size I would say a 3.73 or 4.11 should work up to 33" tires

Way more factors than that. 3 speed th400 now, have an overdrive trans and a 5 speed as well. The FF14 has more than enouugh options to get me where I need to be.

 

[Camo]

Making progress.

 

[Bocephus123]

View attachment 284295Making progress.

Great Rig! pile your friends in time to go Hunting!

 

[dlbleak]

That is one sweet truck. I don’t know what your plan is for wheels and tires but I like the idea of stock as a rock on the exterior look.

 

[BobbyV]

Bought a 2wd 1983 GMC. started the conversion. Got the front axle in and driving again. About to start deciding on which rear and gear ratios. Feeling excited to finally get this going.

Very cool. Can't wait to see the finished product.

 

[Camo]

Slowly making progress. Been traveling a lot and been way too hot. Got my 700R4 rebuilt just gotta get it out n and get rear driveshaft made.

 

[DirtyLarry79]

Very cool truck good luck with all the work