Kenworth Frame bending

I think if you add that inner plate, even if you don't take the bend out, it will stop further damage.

 

If it was me I would add some rails and a possibility beef up the 5th wheel mount.

 

Good luck driver!!

 

That last pic has the cross member I didn't see. But it seems a little far back,but hard to say

 

Good luck

Hope to see some pics on what you decided during and after completion.

 

Speaking from experience.... look closely between the frame and the 5th wheel mounting frame. I pulled mine off because I seen a little rust, plus I needed to get to the air bag mounting bolts, fortunately it is mainly the 5th wheel frame that has rusted. Rust has super powers!! I have replaced all 8 bags and mounts, shocks, wheel seals, slack adjusters, S-cams and bushings, brake shoes, drums, wheel bearings. Mine is a 95 W900, built in 94 according to factory line sheet.

 

You like father Xmas.

 

I have 2 1999 KW's one with AG 200 and the other with AG 400 and i noticed some differences but it might be the year difference.
One is the cross member in the pic from the end of the frame forward is 1/3 as thick as the one on my trucks plus it looks like it was from another truck.
I also have a cross member on either side of the fifth wheel which would put one between the one in the pic and the fifth wheel, the cross members missing would be why you are having frame issues.

 

If you have the opportunity unbolt that 5th wheel assembly from the truck frame, lift the whole thing off and then look at your frame. Those waves in the 5th wheel mount are most likely rust pushing them apart. As I said earlier.... I'm speaking from experience. My mount had about 3 bolts pulled nearly in to from rust expansion, once again, RUST HAS SUPER POWERS. Truck in my avatar is a 95 with 250 inch wheel base, it has 6 cross members behind the transmission if my memory is correct. Hope you get it straightened out.