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Does it matter what angle the upper bars intersect the frame and axle? I'm assuming 45 degrees is ideal but is that a must? I see photos of many that seem to be far less than 45 degrees but haven't found a decent tech article with diagrams or photos to work from. I've got a Tri-4 bar but it came with no instructions.
Mounting them at 45 degree angle will have both upper bars terminating at the same point in the center of the rear axle housing. That's not typically where you want them. There are some systems that have a "Y" shaped locator arrangement that does mount to one point at the center, top, of the axle housing, but that's not a "usual" four bar setup.
The typical angle is more in the range of 30 degrees. The two upper bars should terminate on either side of the housing "pumpkin". If that isn't centered (which it frequently isn't since the pinion is off set) then one of the bars (usually driver side with an 8/9" Ford rear end) will mount right at the flair where the "bulge" tapers to the housing tube. The other side will be a short distance from the flair since you want both upper bars to be at the same angle on each side.
Here's a good photo I stole from Larry M that shows what I'm describing.
Thanks, Bob. For others that may need this info in the future, I found this excellent source with pics:
http://www.webrodder.com/topMenu.php...&AID=109&SID=3
Thanks again,