How bad is the frame rot? i haven't seen a superduty needing the rear portion needing cut so much as rocker panel rot etc.

Once you do cut/replace the frame end look into a non drying rust preventive spray like Fluid Film or NH Oil, or what I use Woolwax. Non drying coatings are really the only way to stop rust on undercarriages and my 99.9% rust free 1999 proves it.

 

It only appears to be at the end where the receiver mounts, I plan on pulling the bed this weekend and further accessing.
Wool wax is the plan after it’s done.

 

Is there any prefered way to cut the frames to splice together?
Or straight cut and a fish plate/diamond plate to reinforce?

 

usually its an angle cut or straight cut as welding a frame together without alignment braces can cause warping from the heat. are you 500% sure you actually need to cut out the bad part? Can't remove the receiver hitch, pressure wash and maybe and some bracing on that part? The frames are just not a common rusting out issue unless its a vehicle say from New Hampshire that was never washed in 20 yrs etc.

If you have never welded that thick of metal before take it to a shop. Its a serious job that needs to be done right esp where the receiver hitch mounts.

 

Ohhh I won’t be doing the welding. From what I see it’s really thin. This truck is in PA, been washed but there’s definitely a hole.
I’ll know more hopefully this weekend, pulling the bed and will post some pictures

 

Cut it diagonal so you can use a fish plate, if you can't weld worth a damn I'd suggest bringing it to a pro don't chance that kind stuff.

 

HERE ARE A FEW PHOTOS THAT I FOUND ON THE INTERNET A FEW YEARS AGO.....MAYBE IT WILL GIVE YOU SOME IDEAS.....

 

Damn yeah mine is definitely not that bad