The Stovebolt Site Forums The Shop Area Engine Shop rear end swap

im finding a lot of issues with my rear gears in my 1940 1/2 ton and was wondering if the rearend out of a blazer or something along those lines would fit in my truck

You can make about anything work, depending on how good you are changing a bracket here and drilling a hole there. You may have some fabrication involved and you may have to weld to the axle tube, which is cast iron, requiring a higher level of skill.

I would say the most important issues to figure out are:

1.)What is the gear ratio/tire size you want to go to? Do the math, figuring out your desired engine RPM for a given speed and pick the closest ratio to the numbers you come up with. Don't forget to factor in any tire size difference. (There are websites that will help you calculate this. Search the Stovebolt forums for keywords like ratio, rear end, axle, etc.)

2.) What width axle do you need? The full size pickups nowadays have a wider axle that will have the tires sticking out of your fenders. A blazer may be better, something from a rear wheel drive car even closer. (You can spend money having a truck axle narrowed if you want a truck axle.) Ford 9 inch rear ends are popular because they are easy to work on (the guts, I mean) and they were used in a variety of applications, so something from a car may be the same as a 1/2 ton truck, but narrower.

3.) How close will something fit with monor modification? Does the S10 Blazer have the correct width with spring mount brackets at the right width?

4.) What bolt pattern are you planning on ending up with? Carrying two spare tires may be OK until you get around to redoing the front end, but it's a pain for a long term solution. (This is why you see guys go with a Mustang II front and Ford 9" rear, or a Nova front subframe and rear end. Then things will match up better.)

5.) Do you have the torque tube (enclosed driveshaft) drivetrain? That would require a different driveshaft and some modification to the rear of the transmission. (I don't know much about this swap, but someone here will.)

So give us some more details and see who can come up with more answers.

The S-10 4x4 is a good width for your truck. A buddy of mine has such a unit under his 41 1/2 ton and loves it. His 41 is 235, T-5 trans etc etc etc, complete driveline transplant.

Justin,

What do you want to do with your 40? Are you building a daily driver, rod or restore?

I will tell you what my rear suspension is then you decide, We are talking about a 1956 Gmc short box truck, i was going to put a 4 link system in then it happened!! I got a sreaming good deal on a 1995 cadillac seville with 300 horsepower northstar engine. One night after many beers and discussing what engine, tranny and so on to put into my chassis one of the buds says Ya know, you could just put the whole caddy front end into the back of your truck and have a rear mounted transverse drive strut type rear suspension that is independent to boot. (just like a fiero)
And so it happened that in the back of my 56 now lives a 95 northstar power plant with the attached 4t80-e, lost the box space but who cares about that. As for the front end I had put a camaro clip on and it is still there with a light weight plastic replica of an inline 6 right down to the oil bath filter. You should see peoples mouths drop, its just awesome. Future holds twin turbos!!

Hey Rattle, that's really cool and ought to hush those guys who get on here and complain every time someone says, "small block Chevy".

I have dreamed about something like that but getting the axles out of an AMC Eagle, S10 Blazer or etc. and turn that Caddy rig sideways, run a driveshaft to each axle and have an all wheel drive.

Hats off to you for having the guts to go there!

One easy swap you can do if you want to keep your original brakes and lug pattern is to just swap the center section out. The open drive center section out of a 1955-62 PU will bolt right in the 40 housing and has the same axle splines.

You will need to change the mounts to solid pads where it mounts to the springs, and the center hole on the pad will need to be drilled about 1 3/4" to the front of axle center.

If you want a cheaper solution for rear axle/suspension check Hydes suspensions, they make a 4 link system that bolts right on where the front spring mount currently resides, $650 US + a good set of coil overs so for about 1 grand you can have 4 link.