Hey everyone, I have a 78 f250 supercab with a flatbed that measures 97" wide, and I was wondering about a couple of potential issues I may run into when doing my dually conversion. Keep in mind that by doing this conversion, I am not looking to gain towing capacity; it is strictly for cosmetic purposes!

1. I know the rear axle is more narrow on the single wheel trucks, and the studs are shorter, but other than that, will a dual rear wheel setup fit without contacting the frame? My truck has the higher gvwr (cant remember what it is off hand), and I have verified that I do have a dana 60, so swapping out to a longer stud shouldn't be an issue; im just hoping that I can do this without swapping the rear axle. I'm cheap, what can I say...lol.

2. Does anyone know what the width difference is between a srw axle and a drw axle?

3. Does anyone know what the overall width is on a factory drw setup.

4. Since my truck has the higher gvwr, it should have the larger 1" kingpin, correct? If thats the case, I should be able to accomplish this by only swapping the hubs, right?

Any feedback or additional info is greatly appreciated!

 

I am fairly sure you will need to get DRW hubs to make it work. I think there is a 3 or 4 inch difference in width and the hubs give you that width. I was reading that on Dana 70's and they are quite close to a 60, whether they made dual wheel hubs for a 60 or not I do not know, maybe they will swap from a 70, you will have to figure out where to get some that will fit. Somebody else will say something I'm sure, they will know more than I do about it..

 

I converted a single wheel from an 84 diesel to duals by using a spacer to push the wheel out far enough to clear the brake drum. The lugs were long enough for this but it is a stupid way to do it. The drums are weaker than a regular dual setup and can break much more easily.
I strongly urge you to find a dual 70 or at least a decent conversion kit.

 

90's, and later GM's used spacers for the front, and you can often find a set in pick a part for $30.

I was considering converting my C20 to Dually for fun.

 

@rogue40; I shouldnt have an issue clearing the drum with the wheel; the wheels im going to run are the 20" eagle alloy dually wheels. I had originally wanted to run the milled down 22.5s, but its more than twice the cost due to the adapters. Im looking at around 1800 for all 6 20" wheels from a place here in the dallas area, and the cheapest I've been able to find the 22s with adapters is 3800. The clearance I'm concerned about is from the hub face to the frame. From what I've read, the offset of the 20" wheel and the oem 16 and 17 inch wheels are all the same. I was concerned if there would be enough clearance between the face of the drum and the frame for the inner rear wheel to fit and not rub. Another reason I want to run the 20s is because I can run a little taller tire to maintain an overall height of 29" that I'm after. This truck will receive 3" drop beams up front with air ride for comfort and for parking low. I would love to make it lay out, but I dont have the patience it takes to swap in a c30 front suspension clip. I will also be installing air ride out back; 2800# bags over the axle with a parallel 4 link. I want to run such a large bag out back because the flat bed weighs a ton, and is only going to get heavier with the underbody boxes and sheet metal work that it will receive.

For the front, that is a great idea, but my only concern is the additional stress it will put on the bearings. Since it wasnt designed for that style of wheel, couldnt it cause premature bearing wear/failure? If you guys don't think it will, I may go this route. Thanks Ziegelsteinfaust.

@wdfp; I'm hoping I can get away with just utilizing the axle and all the components that are already under the truck, but we'll see.

Were all f350s equipped with a dana 70 rear?

 

If you use the proper dual style hubs on the front there is no additional leverage on the bearings. Though the mounting surface is moved out, the offset of the rim brings the center line of the tire back close to its original place over the bearings.