Good 12 bolt posi setup?

[73 C10]

Hey guys,

I'm looking to rebuild my 12 bolt. It's a daily driver. I am thinking of rebuilding with a Eaton Posi. It is 2 wheel drive and I think it has 3.73 gears that feel pretty good with the <200 hp 350 that in it right now. I plan to put a crate engine in it. 350 hp or less.

Will the 3.73 gears work well with more hp and posi? I has a th400 3 speed.

 

[Georgeb]

I think so. I had a 71 c10 with 373 factory limit slip and it worked well on the street.

 

[SkinnyG]

I'm rebuilding my 12-bolt with 3.73 and a Detroit Truetrac. I think this is the most streetable limited slip for me.

 

[MadOgre]

True Tracs are awesome!. If you have the Eaton clutch pack limited slip? just rebuild it with new clutches.

 

[MikeB]

Are you OK with the highway revs with the 3.73? My calcs show around 2900 RPM + T/C slip at 65 mph. If you can live with that, there's really no other issue.

Unless you're running a big cam, looks like your engine probably makes lots of torque at low RPMs, so I'd personally be running 3.08 gears. Had them in my 69 C10 with 29" tires, and even then I wished for an overdrive trans!

 

[Joe383]

The 3.73s will be good with a 350 HP motor but I would hate it with out an overdrive. If it were me though I would do taller gears like 3.23 or 3.08s like Mike suggested and a small stall converter like a 2,000 at the time you do the motor swap. 350 HP will have a good size cam in it and will more than likely require a small stall. Even a 300 HP motor usually will benefit from a small stall converter.

 

[73 C10]

Thanks everyone.

I decided to go with the Eaton posi with 3.73 Richmond gears. My mechanic is working on it now.

I cruz the highway around 65-70. As long as I can pull on someone to pass then settle back down to 70 I'm cool. I think I cruz just under 3000rpm.

I think I would like a 4 speed stick at some point.

 

[MadOgre]

Thanks everyone.

I decided to go with the Eaton posi with 3.73 Richmond gears. My mechanic is working on it now.

I cruz the highway around 65-70. As long as I can pull on someone to pass then settle back down to 70 I'm cool. I think I cruz just under 3000rpm.

I think I would like a 4 speed stick at some point.

Nice! You can always upgrade to a 4L60 later or a 4 or 5 spd ( although the 4 spd wont offer any improvement over what you have already )

Gears are better steep cause there isn't much you can do with tall gears except more HP. And the steeper the gear the better your acceleration will be. Just limits your top speed. Which you can remedy with an OD