I have an early 81 (10/80) f150 4x4 that I am building for a cruiser and I've been doing a lot of research on the infamous frame they used in '80 and early '81 and it seems that these frames tend to crack at the gear box when running larger than stock tires.. I'm not sure if that's just under normal driving conditions or if it's caused by some off roading too. This truck is just being used as a cruiser but I like the looks of a 4 inch lift with 33's, but I'm worried it might cause the frame to start cracking... Do any of you guys have any experience/input with this? I'm fixing to take this truck to the frame shop and have some rivets replaced with grade 8 bolts..

 

My swiss cheese frame withstood sheer hell. Plenty of off roading, jumps, intentional front end collisions, even launching into a ditch and bending the drag link, not a single issue. She's barely out of spec, they're penty strong, you should be fine. Come to think of it, I don't believe the frames at the steering box are any different from a later one anyway. I've seen them crack, yes, but never any more so on the early ones.

 

Never had a problem with my early frame either. And like was said, ALL the frames can crack and the rivets on the front crossmember can become loose around the steering box area.

 

Ranger is right - the 80/81 frame is the same as the later frame at the sector box. I have two 81's with the Swiss Cheese frame and have had no problems other than Dad's cracked at the sector box. I repaired that by welding it up and then adding some angle.

During the resto on Dad's I considered changing to the 82 frame I have. But after carefully comparing them and remembering my Strength of Materials as well as many other engineering classes I realized that the engineers did a good job on the early frame design. The holes only significantly diminish the strength of the frame in the lateral, or side-to-side dimension as the vertical strength is determined by the upper and lower flanges - which are the same between the frames. And side-to-side isn't an issue.

 

Update: I take it to a frame shop and they find that the piece that's welded to the frame that the steering gear box bolts to is cracked in the crevice by the engine crossmember... I don't believe the actual rail is cracked... Is this fixable or do I just need to find another chassis to swap the body over to?

 

It's a gamble with another frame. They have a tendency to crack in this area. I believe there is a tsb on the loose rivet problem in this area also. So another frame may have the same problem.

What does the frame shop recommend. Would they repair it for you for a reasonable price?

 

It is fixable. And Dave is right - they tend to crack there. Here's a link to Dad's Frame & Suspension thread where I fixed the crack on that frame. I think there are pics of the crack on the previous page, and then on this page I show how I ground the crack out and welded it up. Then I mapped out how to reinforce it and did that on the following page.

Also, check the rivet or "Huck Bolt" that is just below that point. See the discussion on that right after the reinforcement.

Now for the disclaimer - I have not tested the fix. IOW, the truck is not back on the road so I cannot prove that it not only fixed the crack-prone area but reinforced it so it will not crack again. But, I know it is much stronger than it was and the reinforcement moved the stress point away from the holes and the back edge of the box, which is why they crack in the first place.

 

Man I wish I could bring mine to you! The body shop said they would fix it for $400

 

He said they would cut a "V" where the crack is and weld it up, he said he wasn't sure how it would hold up

 

Nothing that can't be fixed with a cutoff wheel, MIG welder, die grinder, a vise, a hammer, and a drill. And I'm not that good at welding.

 

Just doing that puts it back as it was from the factory, and that's assuming they do a perfect job of welding. And it cracked from the factory - right? So why just do that? The angle should dramatically strengthen it since the flange of the angle is welded to the flange on the frame. That gives it leverage.

 

I'm not either, I don't have the tools to do it.. Would you attempt to do it again on another rig?

 

If you are asking me to come and do it, I don't think I can. Would I do it again, you bet. It wasn't that hard to do.

 

I'm not asking you to come to me, I'll go to you... This truck is still very drive able and dependable... I'd feel better having someone do it that actually knows these trucks and what the hell they are doing

 

Where are you?