DIY: 3/4 ton rear springs on 1/2 ton

[MalibuSSwagon]

I seen plenty of threads regarding Heavy Half/Big 10 rear springs, I figure I'd share my conversion. I found one of my leafs was broken at the eyelets, so decided I'd do this conversion since I tow and haul heavy items often with my 86 shortbed. Yes, some guys say they don't like the stiff ride, I personally prefer a vehicle that doesn't feel like it's tipping over on every corner.

What you need:

Big 10 / C20 rear leaf springs. Get the 2600lb rated 8/1 springs.
U-bolts. Your spring shop should be able to spec what you need and bend them on site.
Eye bolts, you may have to cut a couple of the old ones.
quantity 10; 3/8"x1" Grade 8 bolts, lock washers, and nuts. If youre near a TSC, you can get them for 3.50.



My bill from the spring shop, that spring part number is for an off the shelf Dayton springs. The u-bolt spec is on there as well, altho you could get away with a 1" shorter height.



Some tips to make this easier:

Remove the bed! Otherwise you'll be working on your back and contorting to get the grinder in awkward places.

Soak everything in PB blaster once a day a week in advance. It'll help to loosen things up.

So set the truck up on jack stands. I put two high lift stands under the receiver hitch and two short ones under the axle.

Remove the u-bolts. Best method I found was to slice the nut with the 4.5" grinder, which will relieve the tension on the bolt. Then you can cut the u-bolt in half with out it snapping at you. Obviously, make sure it's supported by jack stands before removing all the u-bolts.

At this point ,the axle should be loose and the u-bolts and spring plates removed. Now, if you are lucky, the eye bolts should come right out with an impact. I got 2 right out. Otherwise, its sawzall and grinder time! Get those bolts removed and the old leafs out!

Now the tricky part. The old 1/2 ton leafs are 52" long, the new 3/4 ton leafs are 56". Well, GM discontinued the Big 10 in 1979, but they didn't stop punching the holes for the hangers in the frame. You should have 5 holes in the frame exactly 4" rearward of the hangers current location.

Removing the rivets is semi-easy. I chose the air hammer method. You could also grind off the heads if you don't have air.

First, slice the heads, cross is best.



Next, take an air hammer with a sharp chisel and go at them. then use a point bit to knock out the rivet heads.



Once you got the bracket off the frame, bolt it back on in the rear ward holes using the 3/8 bolts. There are only 5, the 6th hole would interfere with the bumper bracket.



Ok now you are ready for the new springs. This step is easier with some help, the springs fit pretty tight into the hangers. Also, if you want to lower the truck, now is the time. You will gain 1.5 to 2" of height with these springs.

Lower the rear end. Slide the eyelet into the front hanger. I also found out, the center pin is not in the middle of the spring, make sure it lines up with the spring pad on the axle before going further. Once you get a bolt thru the front eyelet, line up with the rear shackle. Unless you loosen the shackle bolts, it's going to need some persuasion from a BFH to line up with the eyelet. This is where the helper comes in. Once both springs are lined up, jack up the rear axle so it's resting against the bottom of the springs, then slide it so it snaps into the center pin. Install u-bolts and springs plates, torque u-bolts to factory spec, put wheels on and you are done!



Keep in mind this is only 1/4 of a Big 10 conversion, they also had HD coils up front, 1.25 in thick rotors, and wider drums out back. I would also recommend LT load range C tires. I personally am running an All Terrain 235/75/15 on 15x8" Rally wheels.