I realize this will probably go towards a frame, but Im asking if I should try to find a new crossmember, or find a new frame all-together.
(When I say "new", it means limited rust, not brand new.)

The dilemma is: I got a new truck bed, and I had only the rear tank. The bed is a front tank. I was given the tank, sending unit, and straps to go on my truck to swap the tanks.

Trouble is, the 4th crossmember is severely rotten, and I dont trust it to hold a full tank of gas on a bumpy road. Your thoughts?

 

If the frame aint bad there is really no need to change it. If your frame is shot by all means replace it, but other than that I would just put in a new crossmember.

 

Had the same dilemma on one of my trucks. Frame was nice, but one of the cross members was shot. Just ground off the rivets and bolted a nice one on. Best way is to pull the box to get to it. Not very hard, just time consuming.

 

My frame has some rust holes, no bigger than a half dollar. Around the crossmember in question is very thin. And Ive found some cracks. Ill take some pics soon.

 

Keep us posted. I've not done alot of frame work on pickups, but I'm sure its no different than a big rig. All we do is cut out the bad portion, and then bolt a piece of good frame into a bigger piece of C-channel that will bolt to the frame on the truck, and run a piece of metal on the inside as well for added strength. Can't weld on the frame because it takes all integrity out where the weld is.

 

Definately will keep you posted. Do you have any pics that would explain the repair procedure you use?

 

I'll see if I can't dig any up. I can atleast get a diagram of sorts.

 

Thanks. The earliest i'll be able to post pictures is Sunday.

 

A few differences between big rigs and these trucks is that big rig use heat treated rails, while these old trucks did not. Also, big rigs have straight rails, these trucks do not, there are curves in them which are hard to match up to a piece of channel, as well as inconsistent sizing of the channel. You can splice these frames, then fish plate as needed, which is just a typically diamond or such shaped plate to keep the stress lines from being parallel to the load. Fish plate is needed on the side, but not so much on the flanges of the frame. If you were to cut a frame in half, you would want to fish plate it. To do simple section replacement of the frame flange, it isn't as necessary.

 

Thanks for the info Fellro. I really need to get into my truck a little more so I can figure all that stuff out, but for the time being these are the type of vehicles I tend to work on.






The 5 ton is my assigned vehicle. Most reliable truck we have had this year.

 

The pictures make one understand how Ford terms these things "Light Trucks."

 

We had a large thread on this about a year ago, and I also bought the rear half of a junkyard truck and drilled all the rivets out and replaced most of the crossmembers in my old f150. I had a thin place around the rear pass side spring hanger, and what I did was take a piece of the junkyard frame, cut the top of the "C" off and made it a "L", and inserted it inside the original frame to strengthen it. I didn't weld it, because it had 4 bolts through it from the spring hanger after I drilled the rivets out, and it also had 3 large bolts in the bottom of it from the receiver hitch.

Another guy took my idea one step further and took his junkyard frame, cut the "C" in the middle to make it a shorter "C", and inserted almost the whole frame side into the old frame to double it up to give it strength.

 

That is the best way to do it, as the curves will match better and will double wall. Only downside is rust. If crap and the road treatments get between the rails, it can be bad news.

 

Good tips guys.

Ive been looking around for newer frames, and from what Ive gathered, the frames have the same front horns up to 91.
Then in 92 they changed them and added the crumple zones, correct?

Also, did the 2wd 3/4 and 1 tons have the same TTB mount locations as the 1/2 ton?

 

We are talking the full frame here. Most of the frame is the same, but there are minor differences if you are using the whole frame.

-The very early frames had extra holes in the sides of the frame about midway. I don't know why I am mentioning this since it doesn't really make any difference, but someone would probably say something about it.

-80 thru 86 frames, the very front of the frame where the bumper mounts is different. So if you get a 87-up frame, you might have to rig something to get the early bumper to fit.

-F150 frames and f250 frames are different. F250 is a little bit thicker, and the front crossmember is different, the 4x4 has different mounting points than the f150.

-The f250 4x4 frame has a different front portion of the frame, it's boxed in and cut out for the front leaf spring shackles, and has a rear leaf spring mount. It's different than the f250 2wd frame.

-The 2wd f150 frame is the same as the f150 4x4 frame, except the rear springs are more narrow on the 2wd frame. If you take the spring mounts off the 4x4 frame and put them on the 2wd frame, then your wider 4x4 rear leaf springs will fit the 2wd frame, and everything else is the same.

-And then you may run across a chassis/cab f350 frame. These are dually, and are a different animal from the cab back compared to a regular dually, which has the same frame as a regular pickup. Cab forward they are the same as the pickups, but from the cab back they have a narrower frame that is doubled up in thickness, special narrow leaf springs and a special narrow dually rearend to go with it.