Frame Changes and Differences

There seems to be a lot of confusion in the frames these trucks used, and through its facelifts/generations up until 1996. I know we focus primarily on 80-86 trucks here so I am going to focus on that. If down the road we would like to include differences in later chassis, we can since the underpinnings are almost the same.

Basically, there seems to be some confusion that I feel could be/should be added to the frames section. While we know about the swiss cheese frame and then the later 81.5+ frames, there are a few other differences. I have at one time gotten some photographs, but at this time I no longer have them and will have to get them again. The goal here is to clear up some confusion and myths surrounding the chassis of our trucks. I hope this clears some air and provides some extra knowledge to the website/forum. I will not be getting into engine mounts and perches at this time, just extra info surrounding these frames. Since we have touched on swiss cheese frames in the documentation section I'm going to add some more info surrounding these frames in general.

I will be periodically editing this, if anyone has anything to add please let me know!

Bullnose Frame FAQ

Q: Swiss cheese frames are inherently weaker than the later 1981.5+ frames.
A: See the documentation section based on the swiss cheese frame found here.



Q: All frames are the same with exception of wheelbase length.
A: This could not be farther from the truth. Half ton specific frames, be it on both the F100 and F150 are actually 3/16" diameter in thickness of the rails, and hold a rail height of 6" across the board. F250 and larger trucks employ a thicker 1/4" rail and sectioned spots such as above the rear axle and under the frame are 7" tall vs 6" of the half ton frame. The rails are 1/8" wider in sections of the C channel as well. These frames do not flex as much as the lighter truck frames.



Q: Light Duty F250 trucks are just a F150 frame with 8 lug axles.
A: False. The light duty F250 employs the same frame as the F250HD and F350. If this were not the case, then none of the spring shackles or hangers would be compatible due to rail width and thickness and be light duty specific and extremely hard to find. Since this is not the case, any hanger off any F250 will fit any F250. Not only this, but the engine cradle itself is also a bit heavier than the F150 in that the shorter beams of the Dana 44 TTBHD are mounted in different locations. The shorter beams on the lighter frame had a geometry issue that caused premature cracking in the engine cradle in preliminary testing in 1979.

That being said, the light duty F250 is still a true 3/4 ton truck, and much heavier duty than the standard F150. If that wasn't the case, why bother selling a light duty F250?



Q: Some trucks lacked a frame crossmember if it was only installed with a single midship fuel tank.
A: True, I have actually run into this myself when trying to install a rear tank on a truck that never had one. While the holds were pre-punched out for the factory rivets, the crossmember itself that supported the straps for the rear tank was not there.



Q: The frame horns at the front bumper are the same between all models.
A: True, although the heavier trucks have the leaf spring shackle directly behind it. This area was not factory reinforced, so converting an F150 over to leaf springs is nearly a bolt in affair on this end of the frame. It is a good idea to tether the rails together at this end to reduce the chance of cracking behind the steering box.



Q: No one reproduces the rear-of-front spring hangers for F250 and F350 trucks.
A: False. While this was once true, ATS now reproduces these hangers that were once only available by cutting them off a solid truck. See their footnotes for details. They are available here.



Q: Problematic areas of these frames include what?
A: There are a few areas on these trucks that have been known to be problematic, but not unfixable. At the end of the day, these frames are just nothing but steel, and steel can be properly repaired.

Such areas include the core support and cab mount areas, they are known to rust through. All of these spots today have large frame saver washers available to weld in. If the rear cab crossmember is too far gone, they can be removed and replaced. A lot of times guys will go in to replace their sagging rear cab mounts and find out that the rubber has actually collapsed right through the frame crossmember. This is something to watch out for when checking out a truck for the first time.

Another rust prone area is behind the spring hangers, both front of rear and rear of rear. If those are still intact, usually you'll find behind them has a hole of some sort if you are purchasing a northern truck. Keep an eye on the thickness of the rails as well, you'll find this area and the rearmost crossmember are known to get dangerously thin.

This biggest Achilles heal with our frames is the dreaded crackle crack and steering box cracks. While the front section around the crossmember is boxed, these frames are prone to flexing due to not having a crossmember in front of the cradle. The steering box is on the inside edge just in front of the cradle and when under stress can contort the frame. Eventually, and I've seen this on trucks with no rust, the frames can stress crack at any point on the cradle and/or behind the steering box. Some welding and plating will usually take care of this, but do be sure you know the extent of the damage. If the steering box area is severely rusted, it may not even be worth your time.





As I mentioned I'll be touching up on this but I think I covered a lot of the common stuff.

Angelo Voltura wrote

Another rust prone area is behind the spring hangers, both front of rear and rear of rear. If those are still intact, usually you'll find behind them has a hole of some sort if you are purchasing a northern truck. Keep an eye on the thickness of the rails as well, you'll find this area and the rearmost crossmember are known to get dangerously thin.

A really common rust area on these trucks is the rear upper shock mounts. They are like a cup that captures and holds salt and debris and eventually eats a hole right through the frame. A quick and dirty (and common) fix is to put a plate on the outside of the frame. I've seen many of them like this, and there's a shiny example on Ebay right now with a crusty looking frame.

https://www.ebay.com/itm/163972943658




If you see a rusty frame, there's a good chance you can poke a screwdriver (or a hammer) right through the frame in the middle of the three bolts for the upper shock mount. I had to repair mine in this location, but I removed the mount and grafted a new piece into the frame that can't be seen now.

Another thing to note if you're in the rust belt is that vehicles will always begin to rust first on the driver's side, or worse on the driver's side, so if inspecting a frame or body for rust or weak spots, etc...always pay very close attention to the driver's side first.

Angelo - I like this!  But I have some thoughts:

First, on your answer on the Swiss cheese frames, it looks like you are agreeing with the statement (which really isn't a question) - until you go read the page to which you linked.  You could copy and paste a bit of that page into the answer and say "as explained here" or somesuch.

On frame heights and thicknesses, I think you might be surprised at the differences.  Take a look at the table in this post, which comes the 1982 Dealer Facts Book, as that post does.  You could include that table in your post.

That thread intrigues me Gary. You mention that liner not fitting Dad's truck. The liner on my 86 frame (E7TA ) looks like the NOS one you bought, as it goes between the crossmember and the frame rail. However, I've noticed in your RSK pictures that you were able to stitch weld the frame box bracket to that steering box liner. I won't be able to do that on my truck, because the frame box doesn't come close enough to the steering box liner. I'm not sure if it's a 4x2 vs a 4x4 thing, but I find it interesting. There's even a difference between an 85 4x4 and an 86 4x2 when it comes to the steering liners.

Shaun - Yes, that is an intriguing area.  It looks like there were several changes along the way.  And with the several sizes of frames, that makes the frame liner a complex discussion.

Absolutely amazing responses guys, I've been busy working and will be busy for a few days before I can really dig into this and process all the information, but I will be getting to it shortly.

Love that chart!!!


I'm going to see what I can dig up on that TSB for the steering box when I have a chance to log into my OASIS since I'm a Ford employee. I may be able to get all issued TSBs for these trucks.

No problemo.

I really LOVE to provide documentation that proves things.  And that chart is one of the gems.  

Oops, I missed the TSB thing.  I actually have every TSB from 1980 through '97.  But they are all in paper form so I have to scan them.  So if you can get them in digital form.....

Here's my library:

Gary Lewis wrote

Oops, I missed the TSB thing.  I actually have every TSB from 1980 through '97.  But they are all in paper form so I have to scan them.  So if you can get them in digital form.....

Here's my library:

Gary, have you considered a fire extinguisher [sprinkler] system in your garage?

Hadn't, David.  But, perhaps that would be good.  However, it would have to be something besides water as that would damage the books.