The Stovebolt Site Forums The Shop Area Driveline Want to change rear axle from torque tube to open drive line

I have a '51 panel 3100. I want to install a 5.7L small block Chev engine and
a 4L80E four speed automatic tranny.

What rear axle(s) would you recommend?

I have used the "search" and Tech Tip features but have not found
the info I need.
Jerry

What do you plan to use the truck for? Cruising? Long trips? Towing a trailer?

These answers will help find the right gear for you.

Late 70s to late 80s Camero or Firebird will do it. Cut off the spring perches and weld them where they will line up with your trucks springs.

Martin:

Perfect. Exactly the info I need.
Much appreciated.
Thanks.
Jerry

To clarify Martin's post, second gem camaros and firebird fit nicely. The 3rd gen are wider.

Here's a link that is helpful if you have trouble finding that rear end. Someone correct me if I'm wrong, but I believe the truck rear ends are very close in width all the way up to '70.

http://www.carnut.com/specs/rear.html

Sweet: I live in an area that has a lot of wide open spaces. 75 MPH on the interstates in AZ. and 80 MPH in west Texas. So, cruising for me means I
want to have the ability to keep up with traffic on the interstates. Would like to
use the panel on trips to Texas and Oklahoma. Local cruising... of course. No
trailer.

Fox: Thanks for the link. Outside axle widths very helpful.
How are axle widths measured? Outside of brake drum to outside of brake
drum? Or?

Thanks,
Jerry

Most measure form wheel mounting surface, out side of drums, to wheel mounting surface.

Use one of the online gear selecting calculators to find the best gear ratio for your transmissions and tire size. With overdrive, you have plenty of choices. I would guess 3.73 would be about right with a 28" or 29" tire.

To set the spring perches close to start, measure the old pinion angle compared to the old perches. Level the perches with bubble level, then measure the pinion angle. This should get you close. If you plan to lower the truck, then just clamp the perches in place with the u-bolts, finish up the chassis work, and set the pinion angle very last thing once you have all the weight of the truck on all four wheels.

Always remember, the pinion angle needs to be set when the truck is on the ground, all four wheels on, full weight, and driveshaft in place.

Joe

Are you going to change bolt pattern from 6 to? Need to make that decision first, all car axles will be 5 bolt. S-10 rear axles(4wd models are about 2" wider) are another option. Dana 44(GMC) and 10 bolt(Chevy) 1/2 ton also.

Ed

I used a 12 bolt diff.out of a 1978 4x4 chevy suburban.it has 6 stud axles.also has 3:08 gears which is not ideal for me but I've been living wit has for 25 years. The width is a little wider than stock.when I measure diff width, I go backing plate to backing plate.when setting up your spring perches keep in mind the offset the torque tube diff has.you will need to build new perches to for accommodate this, otherwise the wheels won't be centered in the fenders. I built new perches other will use 2nd series55 and newer rear springs. These trucks use open driveshatft diffs and the springs are different.

Joe: Thanks for the axle measure info.
3.73 is what I had in mind. That's what was in the donor vehicle for the engine and tranny. It was a '97 3/4 ton Chev pickup so the axle will not work for me on that. Will follow your advice on pinion angle and setting the perches !


Ed:
Yes change all wheels from 6 to 5. Have assembled most parts for disk brakes
on front axle. 5 lug.
I'll look into S-10, Dana 44 and 10 bolt Chev 1/2 tons.

Just want to find, like everyone, the simplest swap. I dont' mind re-welding
the spring perches but don't want to turn this project into major surgery that
would probably be beyond my ability.

Once again, big thanks to all who contribute here.
I'm shootin' in the dark and need all the advise I can get.
Jerry

Late Chevy have 5 bolt on 2wd trucks, may slightly wider, though.

Ed

On my last AD truck I used a 79 camaro. It tucked in very well.

Thanks Fox... that's what I'm going to be looking for.
Jerry

I used a disk brake kit that uses the single cylinder calipers and rotors from '70s GM Camaro/Firebirds. So it was an easy choice for me to pick a 1979 Firebird 10 bolt rear axle. This then let me pick a '70s GM manual disk/drum master cylinder. So I basically have a '70s Camaro braking system, 6 cylinder engine, late '70s transmission, and ignition system. What ever fails, I can get at any parts store in any town I go to. So far after 16 years, nothing has failed out on the road!