So, I've ventured over from the AD page. I have a customer's C20 that he wants to lower about 4" all the way around. Can 1/2 ton stuff be switched over to a 3/4 ton? There isn't a whole lot of drop stuff that I have been able to find for this truck. Any suggetions?
Control Arms: I converted my C10 to a C20 suspension a few years back. The lower A-arms are a direct swap (2 u-bolts to the cross member each), but the 3/4 ton upper arms have larger diameter mounting studs than the 1/2 ton. Front Springs: There were only 2 different coil springs used in the front for both C10s and C20s - standard and heavy duty (for diesels and big blocks), so you can use drop springs for a C10. Ball Joints: I did a quick search and read that you can just change the ball joints to 1/2 ton to use spindles for a C10 (No need to change A-arms). I know firsthand that the upper ball joints have the same bolt pattern for 1/2 and 3/4 ton, but don't know about the lowers. One thing you should know, since this is a customer's truck, is that the upper ball joints are originally riveted in; so if they are original, that will add time. Rear Axle: For the rear, you can swap the rear axle for a 12 bolt ('73 - '82) or a 10 bolt ('83 to '87/'91). You will need a 1350 to 1310 or a 1350 to S44 conversion u-joint depending on which axle you get. You will also need U-bolts and plates, although I'm guessing you will be flipping the axle over the springs so you would need those and mounting pads as well. The only other difference I can remember is that in '84 they changed the parking brake cable setup. Rear Springs: The main thing to watch for with the rear springs is that there are two different lengths, 52in and 56in. Most C10s have 52s, and most C20s have 56s. So your parts list should look something like this: C10 Ball joints C10 (drop) spindles C10 (drop) coil springs C10 brake rotors/hubs/wheel bearings C10 brake calipers C10 rear axle Conversion U-joint U-bolts/plates Spring Mount pads Shocks Rims/tires
