[trans_am_man]

My driver's side rear frame rail (1974 F Body) has an inner front section (about 1 foot long or so) where the front of the rear leaf spring bolts to. It was rusted out so I purchased a used rust-free inner front section. I am now ready to weld in the new used piece, but it won't slide into the front part of the rear frame rail

My thinking is to cut off about 9-12" of the front of the rear rail, weld in the inner front section to the floor pans and rocker lip, and then weld the outer frame rail back together and also to the inner section.

I am concerned about weakening the outer frame rail, though. However, it doesn't seem to be a highly stressed location as the factory did not reinforce the area.

All advice would be appreciated before I cut off the front of my frame rail

 

[19673L4P]

a couple of ideas to give a little less concern. when you get back to sound metal on the original rail try to make a angle cut accross the rail (one side should be longer than the other, the longer the angle the more any stress will be localized). if i were doing a rail i would also put some short tabs inside the original and cut the patch 1/16 to 1/8 short so that the joint can be tied better. butt joints without backing can be a little tough.

 

[trans_am_man]

Thanks for the input. Just some more information from me. The 8" section I would be cutting off at the front of the rear frame rail will have the front section inside it. The front section inserts into the rear section and then comes forward and is welded to the floor pan and the rocker. I'll be welding the cut off section back in place, welding along the line I cut plus plug welding it to the front section.

Any concerns? My only other potential option is to cut out the foot section of the rear floor pan (the drop down is in the way) and try to somehow slide it in. Not sure if that would work, and will create more welding.....so I am hoping to get some assurance that structurally cutting off a small section of the frame rail will be ok!

 

[19673L4P]

1st plan sounds fine. i didn't know the piecse would fit inside of the original.