Where do you cut to extend beams

[XTate]

When I study the photos of extended ttb beams, it looks like most everybody is sectioning the beams on the outside of the radius arm bolt hole in the 6 inch section between the bolt hole and the ball joint holes. I understand this location if you want to use bolt on arms. Is there any other reason to use this cut location, If you are going to weld on your arms. Why wouldn't you make the cut on the inside of the radius arm bolt hole in the straight 4 inch section ? The pivot points stay the same, the pinon yoke location stays the same, and you have more frame clearance. Please feel free to school me on this, what am I missing. X

[-JD5353-]

Lengthening where you mention would effect the radius arm mount like you said but I also believe you could run into axle clearance issues there because you would be making a narrower section of the beam longer, it could cause the axle to hit the top or bottom inside the beam during cycling, although I have no solid information if that is true or not, just a guess.

[ESHALLBETTER]

Even cutting the beam out at the end requires you to re-clock the differential. Not sure the effect cutting it further up the beam would have, but I would spend some time investigating.

I'm sure you've seen this but give it a read if you have not.

http://www.gofastbroncos.com/forum/view ... ?f=15&t=10

[arse_sidewards]

The ideal cut and turn would be cut so that your turn is about the center of the U joint. That would eliminate all issues with diff clocking, spline engagement length and passenger shaft window clearance. Everything inboard of the cut section would be geometrically equivalent to stock beams. Obviously that's not practical since and we like wider track width anyway so the best compromise is to move the lower joint outward. Whatever distance you move the lower joint outward you lose half as much spline engagement in the diff and slip yoke. You also move the center of the u joint upward. Imagine if you extended the lower part of the inner C, see the problem? When the line between the upper and lower ball joints is near vertical there's not much of a problem since pretty much all the motion is horizontal. A few thou of vertical misalignment is no big deal but as you move the lower joint farther the motion become more vertical. Pretty soon you wind up having to clock the diff if you want seals and U joints to last more than a very short time.

Once could definitely make a jig (I can think of a way using mostly stock TTB parts and a welder) that allows you just cut the balljoint bores off and do an "ideal" cut and turn about the U joint center. However, the misalignment from a 4"ish cut and turn is still within the range of what's acceptable (IIRC nobody clocks the diff for a 4", they just move the lower out) and you can just slot the diff mounting holes and rework the tab on the outboard side you'd be gaining little compared to just moving the lower balljoint out. It's a case of the 90/10 rule. If you're pushing every other part to the limit and need to use stock style parts (no RCVs or over width beams) then getting the beam geometry at the knuckle just right might be worth it.