Extending TTBs

[JefF250]

Hey folks, hopped on here because most other forums don't have people familiar with TTBs and they're more interested in bashing them than making them better.

I have an F250 with Solo's leaf spring delete kit and I want to extend the D50 TTBs for a couple reasons. From what I understand, it's not necessarily just a simple cut, add material, and extend axles.

I was talking to a fabricator who's done this before and he was basically like this will take too long for me to do so you're on your own. He did say usually he extends the axles first so that the axle is still centered in the window when he extends the beams. I am going to extend them both by 1.75" which I know is not much, but that's my plan.

If anyone has experiences to share some or recommendations I would love to hear it. Thanks in advance for any responses.

 

[JOLENE_THE_RANGER]

it is just a simple cut, extend and add material. heres an example of a +2"
between the 3rd member and the beam end obviously. youll want to extend your radius arms as well to keep em as far out as possible on the beam. also make sure your angles are right on the beam end for camber.
over lay plates on everything for strength obviously

 

[JefF250]

What kind of steel do you recommend? Any validity to the extend the passenger axle first to mock it up centered in the window, or did you extend them equally?

Also, it looks like you simply extended the beam. There is no reason to rotate or turn the beam up and down since mine is already cut and turned at the lower balljoint, just not extended. Tbh I think they're just making it sound more complicated than it is so I don't just do it myself (and pay them).

My radius arms are from Solo, F250s were leaf sprung. They have massive heims and are decently long. That's actually part of why I want to extend them. The location of the radius arm/lower spring perch is just outside of the frame rail at factory full compression, so as designed it loses up travel and forces the spring to bind on the frame rail. I see no reason for it to be this way so I'm doing something about it.

 

[JOLENE_THE_RANGER]

extending it will change the angle of your cut/turn, as it is changing the diameter of the circle that the beam is pivoting on, but not by much. its something youll have to measure and angle the cut in your extension piece.

i only use cold rolled steel or chromoly for overlays. 3/16 thk rectangle tube would be fine for the extension piece.

 

[JefF250]

Okay, so just thinking about it, it makes sense that it will effectively create more negative camber if they are linearly extended. Meaning that I'd either need to lift it more to bring the wheels back to vertical, or I'd have to rotate the beam slightly downward to avoid this. I actually selected a spring that gives me an extra half inch of lift, so I think I might be just fine extending it straight if the difference is minimal.

For the steel choice I figured using something softer would be preferable so that it doesn't brake if over stressed, but bend. The fabricator I spoke to recommended mild steel.

 

[JefF250]

About the metal, I'll go with 1/4" on the extension as it's a diesel. For the plates i was thinking either 1/8 or 3/16. Not sure which one I should go with there. Was also thinking I should box the back where Ford/Dana decided to leave them open.

Thinking about it more, I am not sure if it effects the geometry the way I initially believed, but here's my geometric reasoning. I am going to be extending the arm behind the spring perch, effectively making the spring shorter, and creating less lift by the cosine of the angle the axle/beam makes with vertical. That in effect should make for more negative camber. At ten degrees that makes for less than half an inch of ride height difference (I ride height is probably closer to five degrees). The longer spring I chose should add a little more than half an inch so I suspect that I will be ballpark in the right spot for the turn that the kit was designed for. The one thing I didn't remember to measure today is the beam angle at estimated droop and ride height. Going to have to measure that tomorrow.

I also decided I am going to just do a 2" extension. Might as well stick with a round number. In the future I am going to be adding an axle which is 3" wider in the rear so if everything works out as planned, I will have to add 1/4" wheel spacers to the rear and everything will sit even. I know that math doesn't add up, but that's because of the increased angle of the beams at ride height it draws the tires in by about a quarter inch. I'll let a computer measure that difference before I buy some shim style wheel spacers though. Either that or I will just not care about the difference if it's close enough to not tell.

 

[JefF250]

Okay, I'm pretty set on how I'm doing this aside from one thing. MIG or TIG? I'm getting mixed responses from people with welding experience. Will either be fine for a 2" extension?

 

[scotts90ranger]

Welding mild steel is forgiving, just have good welds, bevel the edges then grind smooth and fish plate over the top of the extension should be sufficient

 

[JOLENE_THE_RANGER]

either will be fine. i usually mig most of my stuff and then tig the overlay plates ONLY because it looks nice lol
only grind the welds that will be covered by the plates so the plate sits flat, leave the meat on the weld everywhere else.

 

[4x4junkie]

I went the opposite way (narrowing a D44 TTB), but basically it's the same concept (having to weld a cut beam back together).

Agreed, it's not real hard to do. Having the differential, axle shaft, and knuckle in place on the driver side indeed will make it easier to center things up for welding it back together. The passenger side is much more forgiving since the shaft on that side has two u-joints, you just need to keep the beam sections lined up well enough so that your welds come out decent (and that your camber matches that of the driver side).