3/4 ton to 1/2 ton swap questions

[chevroletrucks]

I have a 70' c20 with rear coil suspension, I'd like to make it a half ton soon. I also have a 1967 1/2 ton rolling frame to use parts off of, although it's still drum brakes I know I can easily convert that with a kit. My question ,I guess is has anyone on here done this and if so how did it turn out with an earlier suspension? Control arms, width of rear diff. upper and lower control arms swap directly over or do you use the old front crossmember? stuff like that, any input greatly appreciated!!!
Thanx
Joe

[smbrouss70]

Maybe someone else can chime in that actually has this experience, but my understanding is that the upper control arms are the same, as well as the crossmember. Therefore you should only need to change out the lower control arm and the springs, spindles and such for the front. The rear trailing arms should be the same as the 1/2 ton also, but with a reinforcement plate welded to the arms from the factory. So the rear should be just swapping the whole rear-end and the springs.

Again, I haven't personally done this swap, but I believe this to be all that is different based on what I have read here and from looking at the difference between my 70 c10 and my 70 c20 parts truck.

[68jimmy]

I'm currently going thru this process right now. I started with a 68 gmc lwb 3/4 ton and a wrecked 70 chevy 1/2 ton. The gmc came with a leaf rear suspension which I removed along with the middle crossmember that supported the driveshaft. I then used the crossmember from the 70 (it was a lwb also) and a used set of arms from a 66 3/4 ton (the arms from the 70 were rusted thru) and installed new poly bushings. A set of 3" drop springs from GMC Pauls helped bring down the rear... The rear diff is from the 70 as well and it is a 12 bolt 3.07 posi 6-lug pattern.
As for the front I'm getting ready to swap in a disk brake setup using newer parts. There is a write-up in the FAQ section that uses your existing lower control arm, using a 1/2 ton upper control arm, then ball joints, tie-rod ends, spindles and rotors from an 88 - 91 model...

You will be amazed at the difference in ride quality!

good luck.

[stueber68]

I work for a GM dealer and I am showing different part #'s. Everything should swap right over though. The crossmembers for the front are the same. On the lower crossmembers you might find that the u-bolts used to secure the half ton are a smaller diameter. Make sure that you use the larger u-bolts from the 3/4 ton. GM has told me that the smaller ones were replaced with the larger due to issues with them breaking perodically. All of the rear suspension swap is the same for the most part. The 3/4 ton rear trailing arms had an extra plate welded to the bottom to prevent twisting, use them instead of the 1/2 ton arms. If you might have anymore ?'s just ask. I check my stuff reguarly. Good Luck and happy building.