55.2-59 Flatout Corvette C4 IRS questions

[bobinbc]

I'm in the process of building my own brackets to install a C4 rear into my 57. I'm pretty sure I've got most of it figured out except one thing. The problem I'm having is with the batwing mounts clamped into position on the frame, the half-shafts angle back as they go from the differential to the wheel. Hard to capture in a picture but I'd say it looks like about an inch on each side. Can anyone with a Flatout Engineering kit tell me if the axles are angled back or do they run 90* the driveshaft? Thanks!

[svr]

I built myown brackets like you are, ilet the struts dictatewhere the knuckles ended up. Yes they are slightly back from 90 degrees to the drive line. All i did was make sure they were in the same spot on both sides. Have been told the ujoints need an angle to make sure the roller bearing in the joint turn a bit as they go around.

[BIGglaSS]

Yes, they angle back. I built my mounts to where they lie naturally. Check my build thread in my sig...

[bobinbc]

Thanks for the quick replies guys! I thought the same thing about the u-joints but wanted to be sure. I've been watching both of your builds already and I'm amazed at the craftsmanship! I'll try to follow in those big footsteps!

[jwhotrod]

they agle back like that in the corvettes as well. that is to make sure that the ujoints in the half shafts never go out of "phase" by having the shafts directly in line with the spindles and the pumpkin. If that occurred there would be a severe vibration in the direline,

[mr48chev]

On one install I got a look at in this area the guy had hauled home the rear section of the Corvette donor's frame (the yard that sold it to him cut the section out of the frame rather than unbolt it) and he said he took his measurements and angles directly off that frame section when he built his pieces. That isn't always possible though.

[jwhotrod]

its the same principle as to driveline design. you want the u joints on both ends at the same offset to cancel hysteresis or unequal rotation angles from causing vibration in the shaft, Go to inland empires web site there is great info about driveline design there,

[bobinbc]

Originally Posted by mr48chev

On one install I got a look at in this area the guy had hauled home the rear section of the Corvette donor's frame (the yard that sold it to him cut the section out of the frame rather than unbolt it) and he said he took his measurements and angles directly off that frame section when he built his pieces. That isn't always possible though.

Wish I had a shell to take some measurements from, but they rarely show up in the yards here, very little demand for the parts. The one that I boned out for parts left here very quickly...

[bobinbc]

jw thanks I understand the concept. At this point I'm wondering more about the amount of offset, because it makes sense that there is some.

Would be great to hear from someone with a 84-87 rear using the Flatout brackets just to compare notes...

[jwhotrod]

Have you seen QB Racings string in builds titled
1958 SWB C4 Fleetside - NZ Build he is putting 85 c4 suspension in with flatouts brackets. He has posted a great string og videos on youtube search c4 suspension in a 55 chevy truck and they will pop up. I have 1990 c4 suspension in my 55 that I am building with flatouts brackets The batwing sets all of that offset itself the the relation between the pumpkin attached to the batwing and the toe in bars on the back side hold the hubs pretty much where they need to be.

[bobinbc]

I'll check out his videos thanks.

He helped greatly with instructions for the install. Thanks QB!