383 w/ 4sp auto in a 1972 gmc 4x4?

[zed71]

Hi,

I just bought my dream truck. I plan on doing a full body off restoration.

I want to make it a daily driver, and gear it more for toy hauling than a mud monster (although tempting )

Unfortunatly I am 4x4 ignorant.

I'd like to put in a 4spd auto that can handle the 325hp 420ft/lbs.

Can my stock truck axels, transfer case, and a 4L80E handle the power and toy hauling.

Is there a tried, and tested recipe for a trouble free 4x4 drive train?

My wishlist:

383 stroker w/ Holley Pro 950 mpfi
4L80E


Thanks guys. I am loving the eye candy on this site. A lot of talent on here.

[wildwilly4x4]

Sounds like sweet build. 1/2 ton rear axles (10 and 12 bolts) will work with that much power, provided you dont put all that power to the ground while trying to haul toys! You'd really be better off with a 14 bolt out of a 1 ton 73-83 truck, as they will bolt right it, parts are easy to come by at the store, the axle shouldnt ever cost more than $100 unless it has a detroit locker in it. Making the 8 lug wheels match your 6 luggers (provided your truck is a 1/2 ton) is as easy as getting the brake backing plates, hubs and rotors from a junkyard 3/4 ton chevy and swapping them onto your rig. If youve got the coin, swing for a dana 60 front, you wont be sorry if you ever decide you need a stout front axle. I wont run a front axle smaller than a 60, even my lil willys jeep runs a chevy dana 60 up front!

[special-K]

That`ll do.

[Chevy1TonFun]

I'd say you'll be fine with 3/4 ton axles. Run a Dana 44HD front and a 14 Bolt in the rear and you'll never need to worry. What size tires are you going to be running?

[zed71]

Right on. I like the idea of a 14 bolt rear.

I was thinking of doing a 2 inch lift, and putting on Michelin ATX M/S. I'd like to a rim that I can put on a set of 265's and not hang out the wheel well too much?

[vtblazer]

If you drive smart, those 1/2 ton axles would be fine with the motor hp your considering, not a ton of power there and with 265's, not much issue for breakage especially on the street just running around or towing.

Either more power or more rubber (36 & up) would make me upgrade to larger axles but at this time (IMO) if I was building it, I'd save the coin and keep the stock axles.

However...
Run the motor specs and find out where it's going to be making the power, then gear accordingly from there.

If you need to re-gear the 1/2 tons, that would be a waist, that's the time to get a new axle set.

Welcome to the board!

[zed71]

Thanks guys. Since I pretty much blowing my whole budget on the engine/tranny combo, I think I'll keep the stock axles for now.

Is there any point in re-gearing to a 3.08 or 2.73 ratio to save on gas (since this girl will be seeing mostly highway miles)?


Again, thanks Guys for humouring the noob.

[vtblazer]

Originally Posted by zed71

Thanks guys. Since I pretty much blowing my whole budget on the engine/tranny combo, I think I'll keep the stock axles for now.

Is there any point in re-gearing to a 3.08 or 2.73 ratio to save on gas (since this girl will be seeing mostly highway miles)?


Again, thanks Guys for humouring the noob.

You didn't mention a tire size but with that 4L80E having over-over drive, those 3.08's are already way to much.

Decide on tire size, find out the best cruise RPM's for the motor and then go to the gear charts to find the optimum gearing for your new ride.

There's a thread on here somewhere I posted a few good gear charts...just need to find it, stay tuned.

[zed71]

Originally Posted by vtblazer

You didn't mention a tire size but with that 4L80E having over-over drive, those 3.08's are already way to much.

Thank you. Sorry I can't search this forum yet, thanks for looking that up.

I plan on running 265 70R17. Nothing too crazy