J Truck Frames

[Rock]

I'am in need of information concerning J Truck frames. I'am rebuilding my 73 J4600 and the frame will not handle the upgrades. I would like to know if someone out there could tell me the differance between the 73 J4600 frame and a late 80's J20 frame. Can the J20 handle high torque and a 1 ton suspension? If not, can it be beefed up?
I would appreciate any help with regards to frame knowledge for this upgrade.
Thank You
Rock

[Mud Thrasher]

I know that the j-20's came with the heavy duty axles so you shouldn't have a problem there. As for torque it all depends on how much torque you are putting to it. If you are going to build it from the ground up then you can put what ever you want and modify it to fit your application. All you need is time and a welding machine. The 4600 is pretty heavy duty why will it not handle what you are doing? Also, what exactly do you want to do?

[Rock]

Mud Thrasher,
Thanks for your response. My goal with the J4000 is to tow a Jeep (of undetermined type, probably a TJ) with a new overhead camper (most likely a Lance W/GVW of about 3000 lbs). I want to use the J4000 as an allaround RV type truck and keep everything Jeep.
When looking at the J4000's frame, I noticed that the leaf spring mount's limited any heavyduty applications for the longterm. I also wanted to be able to use other spring applications (Chevy, Ford or Dodge) to ensure an easier parts source and a better load capacity. There's also greater choices in aftermarket suspension lift's.
Overall, I'am installing Dana 60's, 502 Chevy crate motor and either a 4 or 6 speed auto trany. I havn't decided on what type of transfere case to use as of yet. So you see, the frame is going to be the key factor and foundation for this project. I'am checking the Jeep salavage yards in my area for J20 frames. I just needed to know if anyone out there had knowledge or experiance with J Truck frames.
Thanks again for your response.
Rock

[PAJEEPER]

I can tell you it actually wont be much different than your J4600 frame. Except the leaf spring mounts are better. The J10 and J20 longbed frames are the same. I have a J10 frame under my J20, no difference at all that I can see. I would look for a J10 or 20 longbed frame. And if you really want strength box the whole rear section from the transfer case back. It is already boxed to a little behind the T-case. What ever you do though replace the rear crossmember that the bumper mounts to with some channel steel. It is way to thin and held on by rivets.