84 c10 12 bolt

[Z7master167]

My truck has 3.08 gears, swapping in a 6.0. It doesn't have positrac so I will be installing one, question is should I keep the 3.08 or go with 3 73?
What the benefit from one to the other

 

[73c20jim]

Not much.

 

[78C10BigTen]

What trans are you gunna run? That would be a thing to cause concern so ive been told. My 78 has a th350 and a 308 gov bomb posi, ivd been told swappin it to 373 would murder my mileage as theres no OD. Theres many knowledgeable people here that could help.

 

[rpcraft]

Yeah it will impact your performance regarldess and economy no matter what transmission you have, the main difference is the OD trans will help compensate for it, especialy if you are running an OEM sized tire. The 3.73 gear swap is also going to throw off your speedo unless you get the correction kit for it so be prepared for that.

What you want to do is report back with what trans you have and what your current tire size is and we can probably help tell you the impact it will have overall.

 

[Z7master167]

Trans is 4l80e not 100% on tire size yet I just know I'm putting 22s on it, gonna do a 5/7 drop for how but plan to bag it

 

[rpcraft]

With the 4l80e and a 3.73 you could run tires up to a 33 inch ok. Wheel size doesn't really matter but with that size it sounds like you will just be driving from one of the three circus rings to another.

 

[dvdswan]

I think the 84 rear axle is a 10 bolt. With normal driving you will be fine. If you are going to hotdog the truck you may think about swapping to a 14 bolt SF. I think they make a 5 lug conversion for it, I know you can find a 6 lug version in heavy duty 1/2Ts or light duty 3/4Ts.

If you plan on towing regularly you will want to have the lower 3.73 gear, otherwise the 3.08 or even 3.42 would be fine.

 

[Z7master167]

I think the 84 rear axle is a 10 bolt. With normal driving you will be fine. If you are going to hotdog the truck you may think about swapping to a 14 bolt SF. I think they make a 5 lug conversion for it, I know you can find a 6 lug version in heavy duty 1/2Ts or light duty 3/4Ts.

If you plan on towing regularly you will want to have the lower 3.73 gear, otherwise the 3.08 or even 3.42 would be fine.

I believe it was factory with 10 bolt but somewhere it has been changed to a 12 bolt

 

[rpcraft]

The only catch 22 is that the 4l80E has a taller first gear, so take-off will be comparably worse than with the th350 or 4l60E. The 3.73 gears and 6.0 will help overcome that, after all it is kind of the recipe for many HD GM trucks out now, I think the main difference is they do still use a 4.10 in many circumstances, even with the factory tires.