9-inch Fab - need perch distance

[68bowtie]

I'm welding new perches onto a 9-inch to bolt into my 68 sb c10 with trailing arms. I've got everything ready to weld in place, but I want to double check the stock perch distance from center to center. Can't seem to find a reference. Thought maybe someone could crawl under theirs and measure what they have on a stock rearend.

I'd appreciate the help.

[BigSky71]

I put a 9" in my truck but I don't know the distance you need, my truck is stored elsewhere for the winter.

Anyway, I installed my 9" onto the trailing arms and bolted everything in then measured it back and forth for about an hour [had to be sure]. Then I tack welded the perches in place. After that I took the rear end back out and finished welding the perches to the tube. When I got it aligned the guy told me the rear end was installed very straight, I was quite happy to find that out!

[68bowtie]

Thats what I plan on doing. I've got it mocked up in place, with trailing arms and springs installed. But it looks like the trailing arms may be pushed in or out slightly due to the spring pressure, and may be causing the distance between perches to be incorrect. I'd like to try and match a stock 12-bolt perch distance to be sure everything sits in the right place.

[BigSky71]

I gotta it now, makes sense. I will go out in the snow today and measure my old rearend and see what I come up with for a measurement.

[snacob14]

I'm sure someone will chime in with the exact measurements, but if not. Just make sure that the top and bottom bolts of the spring are on the same vertical plane.

[smbrouss70]

I got a few measurements for gringoloco in this thread. http://www.67-72chevytrucks.com/vboa...d.php?t=217421

[68bowtie]

Keeping the spring bolts in a vertical line makes sense. I measured the distance between the top 2 spring bolts (35") and the bottom 2 bolts (36.5"). A difference of 1.5". The arms are obviously bowed out from spring pressure.

According to smbrouss70 the distance between the 2 rear u-bolt holes should be 41.25". I'm measuring 42.75". Same difference of 1.5". These are rough numbers but should be close. I think this should work...

Thanks guys.

[crazy longhorn]

Why not build a welding fixture, that fits the saddles of the stock rear(pinned to the pads on ea side? Lay it down on the welding table, set the new perches in place, set the new axle in place /center/ set pinion angle & weldb crazyL

[68bowtie]

Not a bad idea. Too bad I sold the 12-bolt...

[LostMy65]

Originally Posted by crazy longhorn

Why not build a welding fixture, that fits the saddles of the stock rear(pinned to the pads on ea side? Lay it down on the welding table, set the new perches in place, set the new axle in place /center/ set pinion angle & weldb crazyL

Thank you for this post.
I know this is an old thread, but that's a great idea.

[crazy longhorn]

That is the slickest way I have found, & while it takes a tad more work, I plan to use it on the next(3.73,complete diff swap) in my old "money pit" crazyL

[LostMy65]

Originally Posted by crazy longhorn

Why not build a welding fixture, that fits the saddles of the stock rear(pinned to the pads on ea side? Lay it down on the welding table, set the new perches in place, set the new axle in place /center/ set pinion angle & weldb crazyL

Originally Posted by crazy longhorn

That is the slickest way I have found, & while it takes a tad more work, I plan to use it on the next(3.73,complete diff swap) in my old "money pit" crazyL

The critical point that gets repeated in all these axle swap threads is the pinion angle.
With your method, it would seem you'd be getting the perches welded perfectly placed as they were on the original axle.

Similar to my 'Power Steering Box Template' thread, the placement of the perches would be based off the original axle. It seems to me this would be the better method, not to mention all the work being done out from under the truck.