K10 vs K20 - a few questions:

[SS Tim]

Originally Posted by Vintage Windmills

...
Tim, the section modulus you posted for the K10/K20's seems low relative to the C20 based on the dimensions posted. My mechanics of materials book isn't handy and I'm feeling lazy so i haven't checked the math yet.

The number is consistant over the years I have researched. There really is not that much material difference between the two.


Also for those that have no idea what all this means here is a blurb from a board member lukecp.
Well said and clear ...

"I had a course in Mechanics of Materials last semster, which is basically calculating stresses and strains in deformable bodies (beams, pipes, columns, ect), along with deformation, ect. I don't remember going over it, but I cracked open my book from the class and this is what it says:

S = I/c, where:
S = Section Modulus
I = Moment of Inertia
c = Distance from Neutral Axis (center of gravity) to edge of beam

The section modulus is used then to calculate the maximum stress in any section of a beam using the formula:

Max Stress = -Mr/S, where:
M = Resisting Moment. This is the moment (think a rotational force, like a torque applied) that is resisting the forces applied to a beam. If you had a steel beam solidly attached to a wall, where the beam is free at one end, and hung a weight from it, the resisting moment would be the torque needed at the attached end of the beam to resist the force of the weight of the beam and the added weight, and keep the beam from ripping out of the wall.

It also says that the section modulus becomes larger if the shape of the beam is altered to concentrate more of the area as far as possible from the neutral axis (center of gravity). This could include raising the height of the "C" channel, making it wider, or having a frame with thicker horizontial sections than vertical sections. I'd assume that the frame is "taller" than a C-10 frame, but every C-20 I've seen has had a frame that looks identical to my C-10. The frame could be wider, that is my guess for the difference.

So, what does all of that mean? The larger the section modulus, the smaller the maximum stress in the beam caused by the weigth of the truck and whatever cargo or trailer is being carried/towed. So, a larger section modulus causes a beam (or frame in this case) to be able to safetly carry larger loads without deforming or breaking.

In this case, increasing the section modulus from 2.7 to 3.48 would decrease the maximum stress felt in the beam/frame by 22.4%. "

[jocko]

ok, thanks all, I'm gonna go grab my hammer and hit a nail in my garage. You know me. 'Ol hammer....
Now where did I leave those vice grips?

[mrein3]

Besides HEI cap clearance, the biggest advantage I see to leaving the t-case in its spot and moving the engine forward is stuff happens. And by stuff happens I mean stuff breaks.

If you put in a 700r4 and leave the engine in its spot, thus modifying driveshafts, you're no longer looking for stock pieces when you break a front or rear shaft. (I know they usually don't "break" but u joints freeze, the front shaft no longer moves in and out due to lack of maintenance, etc).

If your 700r4 goes out and you're down on your luck, you can just re-install your th350 and put the engine back to where it was.

I don't mean any disrespect to anybody but in my opinion the more stock pieces you use the better and easier chance you have down the road of fixing stuff.

Another thing to consider, and I don't know if its possible, would be to install a gear vendors OD unit behind the transfer case. Think about it. I don't know what you possibly would need OD for when you also need four wheel drive. The only time I get out of 1st gear in my th350 when I'm in four is when I'm driving across the lake and then I never get to 3rd. Then when you're in camper mode and driving down the nice dry slab you have the t-case in 2 and the lock outs not engaged then you could start using the OD.

Personally I would just go with a 700r4.