what axles should i use??
 

I am in the process of turning my 72 C20 into the truck I need. the plan is to go from a c20 to a 4x4 k30 dually. It will be a custom flatbed to haul a car on and then also pull a double/triple car trailer a dozen times a year.

My question is , what axle assemblies should I look to get to handle this work load? I am looking for a pullout 6.0 with 4l80e and transfer case to use for the power plant. I am going to lengthen and box the frame for the bed I need, so fabrication and mounting wont be a concern. most this truck will be fabricated to meet my needs. just looking for advice on what axle assemblies I should use

thanks

Re: what axles should i use??
 

If going with 6.0/4l80/np241, then the best n easiest and also hardest n most expensive is a 78/79 Ford high pinion 60. It has driver side drop so matches output of tcase. Or get a pass drop 241 or modify an np205, then could use cheaper n easier to find GM 60 n matching 14ff rear.

Re: what axles should i use??
 

If your serious about making a car hauler I would ditch the C20 and find a 157" WB C30. Then find a 4x4 for your front axle spring hangers, use a Dana 60 in front and you can keep your rear or go with a 14 bolt. Your going to need that beefy C30 frame to do what your talking about.

Re: what axles should i use??
 

And if going drw, be aware that c&c axles are narrower than dually axles. So that will have a effect on your bed width..but I also agree with above. D60 up front,14b in back...
Also be aware this is gonna get expensive really quick...adding a pass side drop transfercase to a 4l80 costs ..
Np241s and adapters are hard to find ..other option would be the Ford axle mentioned above with a driver side pumpkin..
Along with a stout frame

Re: what axles should i use??
 

Thank you for the help. The frame will be boxed and strengthened for the job. I researched alot and found almost all 20/30 frames are of same spec. (Not the easiest info to find)

One question is what about a mp1625hd transfer case? I understand that I would need a custom drive shaft, but it is factory transfer case for the 6.0/4l80e combo in -07 up pickups. Would it work?

I do worry about keeping cost down, but that has also prolonged this project ten years already by changing my mind alot. I'm to a point I need this truck done and usable sooner than later so I need to start somewhere. I feel this will be easier yet than doing a body swap onto a newer chassis. But always open to suggestions and finding the easiest route due to time

Re: what axles should i use??
 

I should also mention, when I say car hauler, it won't be a full ramp truck. The cars I haul are small for derbies and it will be a modified 12 ft flat bed

Re: what axles should i use??
 

any GM transfer case made after 1988,,with the exception on the np241, will be a drivers side drop t-case...they will not work with a pass side differential front axle..

Re: what axles should i use??
 

going with a full deck and probably 8' wide, you could also look for a Dana 70 HD that was used in the pick-up duallys. That rear is almost 8' wide with the tires on. 4'' diameter axle tubes 1/2'' thick. Diff is a beast. I think if you find an early 241 rhd off of a turbo 400 (32 spline) it will bolt on to the existing adapter. Then you can use the chevy front 60.

Re: what axles should i use??
 

Easiest thing to do would be to find a K30 dually donor. Factory the dually will have the Dana 70 HD rear and the Dana 60 passenger drop front. But everybody wants the front axles so it is big $$$. Usually a $1500-$2k for a SRW and $1000-$1500 for a DRW, so in that sense you are ahead because the dually setup cheaper.

The 70HD is not especially valuable and probably no stronger than the 14 bolt, but GM considered it so in the dually trucks.

Re: what axles should i use??
 

Some may not like this but I suggest looking into the later model AAM axles. Can be found pretty reasonable. I am using a 2006 HD axle in my 72. Factory disc brakes. Lockers are a bit spendy though. As far as the front and a Dana 60, getting hard to find at least here in Ca.

Re: what axles should i use??
 

I’ve got two of the AAM 10.5 disk brake rears waiting for future projects. Theres one other option here that’s kind of been mentioned but not directly. In the late square suv/cc years might even be 91 only you could get the np205 in the crew cabs behind a 4l80E as well as well as the 241 in passenger side drop behind the 400 and 4l80E. I’ve seen several of the passenger side drop 241s late 80s early 90’s square suburbans. They are around still not that common but around. My personal choice however would be a turbo 400 spec 205 which can be built from any gm 205 with a little machine work and parts. You can buy new th400-205 adaptors. With the turbo 400 adaptor you can bolt the 205 up to the 4l80E. It just requires the right transmission output and 205 input shaft. Hard to beat the durability and simplicity of the 205 in my eyes. I would also recommend a Dana 60 and A 10.5 14 bolt in GM or AAM both are essentially the same internally. I will say the 2 piece hub seals on the aam are far superior to the original style GM hub seals on the old 14 though. I’ve been using the later hub seals on the older axles for a few years now with great results.

Re: what axles should i use??
 

You could also go T400/np205 right to a LS...no od but would be a easier to find option...