Camber after NBS 8lug and 9.25 swap

[Hipster]

I want to frame swap myself, and admittedly I haven't scoured online for frames, but if the amount of ECSB 8 lug 2500s on the road are any indication of what lies in the junkyard them's slim pickins.

There aren't a whole lot running around here either so sourcing one is the big part but if you can get one it's the way to fly. The 2500 frames are taller so the upper control arm mounts are in a different location in relation to the lowers. If you can get static settings correct you could still have issues. The vehicle might drive straight down the road but these types of geometry issues reveal themselves under different driving conditions. Such as a loaded vehicle on a long left sweeper, you hit a pot hole and the vehicle changes lanes all by itself. if you've never experience a situation like this with a geometry related issue it's can be an ass puckered up pulling the upholstery off the seat kind of moment. Camber gain can affect toe settings and add to bumpsteer so there's a lot more to it then just getting the stuff bolted on and the static alignment setting correct.

 

[Supercharged111]

Yeah, that's why at the moment I just wanna shove the big diff in by itself and leave it. UCA, LCA, and tie rods all need to have similar inboard and outboard mounting points and must sweep a similar arc to have usable geometry. And the arms aren't defined by their angle, rather the angle of their respective inner and outer pivot points. The LCA mounts being lower on a 2500 is a new one for me, a frame splice sounds like the easy way to go. Z cut, weld, fish (?) plate it and go.

 

[98chevy2500SS]

What the fun in spending 14 hours or less swapping a frame when you can spend days on end doing it this way. LOL

Lol!

The 2500 frames are taller so the upper control arm mounts are in a different location in relation to the lowers. If you can get static settings correct you could still have issues. The vehicle might drive straight down the road but these types of geometry issues reveal themselves under different driving conditions.

Exactly, we had to do that with my UCA mounts, they had to be moved up about an inch.

 

[Supercharged111]

Lol!


Exactly, we had to do that with my UCA mounts, they had to be moved up about an inch.

By the sounds of things, your LCAs should have been lowered too. I'm gonna have to get some pics of my dually to compare to my 1500.

 

[Hipster]

Yeah, that's why at the moment I just wanna shove the big diff in by itself and leave it. UCA, LCA, and tie rods all need to have similar inboard and outboard mounting points and must sweep a similar arc to have usable geometry. And the arms aren't defined by their angle, rather the angle of their respective inner and outer pivot points. The LCA mounts being lower on a 2500 is a new one for me, a frame splice sounds like the easy way to go. Z cut, weld, fish (?) plate it and go.

I' m not sure the LCA mounts are lower but the 2500 frame is taller. I don't have exact measurements but lets just say a 1500 frame is built on a 4 in channel height and a 2500 is built on a 6 inch channel height so the UCA mounts are higher. There's more distance between the UCA and LCA mounts. I've never compared spindles heights between the 2 but imho the 2500 spindle is probably taller so if you do 2500 spindles combines with the lowered UCA mounts on a 1500 you've changed angles and the arc in which camber gain happens by a pretty good amount.

Cutting the UCA mounting section out of a 2500 frame and grafting it in could be possible. 4 slotted tabs hold the UCA on so if you have a 2500 frame you could look at and measure for reference it wouldn't be that difficult to make the mounts from appropriate stock on a backing plate and weld and box it in to the frame where they need to be

 

[GMC Burbalade]

8 lug frame steps down by 1" behind the first body mount, where the 6 lug frame is straight.
In reference to the rest of the vehicle the 8 lug LCA and sway bar mounts are 1" lower than the 6 lug mounts. Upper control arm mounts are 1" higher on the 8 lug frame. Steering box on the 8 lug frame sits 1/2" lower than it does on the 6 lug frame.

In total, this means there is 2" more vertical spacing between the UCA and LCA mounts.

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The front frame section (the boxed part) is welded to the rest of the frame just behind/underneath the firewall. At this location, the 8 lug Suburban k2500 frame and 6 lug Tahoe/Yukon k1500 frames are the same height. By grinding down the old welds you can remove the front and rear frame sections that are sleeved together, and build a custom frame that is identical to what GM would have built had they offered your desired combination. No need to cut through frame rails, or plate them back together. It's all Lego.

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[Supercharged111]

I would imagine the 2500 frame is thicker, that's the only place you'd lose out there. It looks like there'd be no gap between the top of the frame and the bottom of the core support on a 2500 compared to a 1500. Such subtle differences make you wonder why they did it that way in the first place.

 

[GMC Burbalade]

Gap between the frame and core support is unchanged.

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[Supercharged111]

It was tricking my eyes. What other renderings do you have up your sleeve? That makes more sense now, I knew 8 lug frames were thicker (though to an extent it depends on wheelbase) and that they had rear leaf spring gussets, but never knew about the front being that much beefier.

 

[454cid]

I wish someone made new frames for our trucks, like what you can get for jeeps and Landrovers.