The Stovebolt Site Forums The Parking Lot Big Bolts most economical hi-speed rearend for 1/12 ton dually?

hello fellows and ladies,
Walt Here, I'm new to the forum. I've been cruising this forum for a few months and just figured out how to join. We're just an old mom and pop speed shop. Our shop is 80 miles east of Raleigh in ECU territory. We cater to Vets, Warriors and our service men and women. We figure if we can get the hands to work the mind will soon follow and we have success with that in mind. No gov funding so it's mostly out of pocket as to any funding. I'm a LBK amputee myself and identify with hardship and frustrations some of our brothers and sisters face.
Right now we have a few projects going on. 37 Ford 2 dr Coupe, 41 Ford business coupe, 2 miscellaneous 1/2ton trucks and this 54 dually 1-1/2 ton chevy. This is our first BigTruck project. I've skimmed through the 12 pages of rear-end postings. WHAT is the most economical way to move to a hi-speed rear-end|? Right now the 235 and 4 speed work wonderful. Thoughts of a 350 and 700 are under consideration but still need to get off of that gas guzzling granny rear-end. I don't expect we'll be hauling any weight and want to actually make this a 4 door truck if we can locate another cab reasonably priced. No thought or plans of lowering the truck at this time but we are having brake issues. Just found Universal 1 1/4" bore cast iron master cylinder for large brakes with dual cylinder on eBay since we've already had an incident with brakes. Tires, we will have to deal with later as money allows. Any and all info is greatly appreciated.

With thoughts of extending the cab I'd rethink the 700R4 trans, thats a car transmission for the most part. If you at some point enter a parade with 10-12 Vet's in the back bed and 3 or 4 up front the trans may not be strong enough.

If it were me I'd leave the truck stock and take the slower roads.

Mike B

Any faster than what you are going now, wind resistance is going to be an issue with a 235. A 235 needs RPMs for HP. If you are considering making a 4 door out of the cab, I would consider setting it on a later model chassis that will give you the desired speed.

Hi Walt,

As the boys are telling you, the 235/sm420 combo is at its performance limits with a Big Bolt in its stock configuration -- if you start modifying it, you make the truck pretty much undriveable.

Bottom line -- for safer, higher speeds, you need to switch out the driveline completely. It's a lot of work whether you just switch out engines and axles, or if you switch the body over to a modern chassis.driveline.

Grigg (moderator for this forum) is in the midst of doing that to a 2-ton and you can see his project here

Whichever way you go, there's a lot of expertise available to you here. Stay in touch with us and post some pictures somewhere (like photobucket) so we can see.

Thanks,
John

The single speed rear ratio will be 6.17. A two speed rear has 6.13 or 8.10. I have much the same truck and after a lot of thought I went for a later 6 cyl petrol straight 6 and a five speed. This lets the truck run about as fast as you would ever want to go on stock suspension and brakes. Its nice at 55 and at 60 the limiting factor is the suspension and the violence of the bumps. The driver needs to have no back or spine problems.
As everyone here says above- get a new platform if you want to go any faster, but thats just not the same and the classic truck is gone forever. Better yet, Resto-mod it, update the minimum, sit back and enjoy the ride.

The only reasonable way to gain more speed,would be with an over-drive installation. Sometimes you can find them on EBay. They're posted in the "Swap Meet" section,here on "Stovebolt.com,too,(seldom,but sometimes),but they sell pretty quickly. I've been looking for one,(locally) for the last 2 years,but can't find one reasonably priced. If you go that route,you'll need a linkage for the shifter,and a cross-member mounting bracket. You'll have to shorten the drive-shaft,as well. On the "Plus" side, you Gain speeds! A 3-speed will give you 12 speeds,and a 4-speed will give you 16! Just make sure that you purchase an Over-drive unit,NOT a Direct-Drive. Here's a video,of an installation,(Brown-Lipe 5531),in a '70's Chevy C-65 ...https://www.youtube.com/watch?v=EEZAalMfSbw

Hello, oldmanwalt,

My 2-ton 54/55 GMC COE flatbed will be in Jarvisburg, NC by noon tomorrow. We will in residence in NC no later than July 2016.

You are about 3 hours from Jarvisburg. Maybe we can meet each other in a year or so?

I plan on driving my 2-ton at speeds between 45-55 (270 GMC engine, SM420 transmission, and 9.0x20" wheels/tires). I have a Clark 5-speed overdrive but I do not know if/when I will install it. 45-55 mph is OK by me.

Thank you for your service,