Please help me out with my 71 GMC 3/4 ton

[Angelo]

Hi! ive been on this forum for a while i just havent intruduced my self. My name is Angelo im 22 yrs old and i have a few 67-72 chevy, GMC trucks and suburban projects that i have bought over the last 6 years. My main project im working on right now is my 71 GMC 3/4 truck i am wanting to converted into a dually. And dont know much about the conversion of a 3/4 to a dually. I will appreciate any help i can get. Thank u and when i learn how 2 download pictures i will post pictures of all my projects. I like getting on this page and seeing everyone out there that is obsessed with this trucks and suburbans like me lol

[tecky11]

im not an expert but i do know that you will have to either shorten you r rear end for the duallies or buy a dually rear,and some spring mods.

[Sacramento70]

...as well as adding wheel covers to the bedsides

[Angelo]

R there any adapters to ad the dually wheels instead of changing the differental?

[tecky11]

i STRONGLY suggest that you dont use adapters. They can be very dangerous and a pain if you have to tighten your lugnuts. find a local junkyard and get another deully off the same year truck and it should just bolt right up

[WIDESIDE72]

I havent made the swap on a 67-72, but have done 73-87 and 88-98 trucks and it should be similar. By the way, there is a difference in a "dually" (pickup bed with extra fenders tacked on to cover the extra width of the additional tire) and a cab and cassis with dual rear wheels. GM never built a 67-72 "dually". The rear axle on a 3/4 ton is wider than on a 1 ton with dual wheels. If you add dual wheels to the rear of a 3/4 ton truck, you will need to plan to cover the exposed rear tire.

As for the rear, both trucks had the full floating 14 bolt rear just like a 1 ton, so we simply unbolted the 3/4 ton wheels and bolted on the 1 ton duals. The axle studs were already long enough.

For the trucks, on 73-87 and 88-98, were were able to swap he 3/4 ton hubs for 1 ton hubs. I can't remeber for sure but I think we were able to reuse the 3/4 ton spindles. If not, the 1 ton spindles swapped on with no trouble. In any case, it was a bolt on deal. With both trucks, they had custom welding beds my dad built, so he bought some steel trailer fenders, sectioned them down the middll and welded then to the bed to keep the bed from being so wide. (As opposed to making the whole bed wide enough to cover the tires.

[WIDESIDE72]

IMO, when GM introduced the "dually in 73, they basically took a 3/4 ton and did what we are talking about here. They were able to offer increased towing capacity and stability without infringing on the ability to haul a 4 x 8 sheet of plywood ( or equivalent load) inside the bed, which was not possible if they added a pickup bed to a cab and chassis.

[WIDESIDE72]

If you look at a modern "dually" from front to rear, you will see that the inside rear tire is in line with the front tire, and the outside rear tire hangs out in the wind. On a "cab and chassis", the rear outer wheel is either in line with the front wheel or the front wheel splits the middle of the rear wheels, i forget. Basically a 3/4 ton rear axle is the same width as a dually. A 1 ton cab and chassis rear axle is narrower