1973 Plymouth Duster repair and rebuild


@RustyRatRod I recall you providing quite abit of info on Axle geometry on a thread I was reading up on, hopefully you can provide some insight.

Everyone who has a thought, please chime in.

I am under the assumption that I am using the pinion angle numbers found in relation to the perches being the 0 degree reference when installed. If I am wrong there, lets start with that. I have read people comparing it to the transmission output. And maybe that number is different than the relation between perches and pinion. I just want the axle perches set to OEM a-body to get started with.

As you can assume, I am now at the point of trying to weld in my perches on the ford 8.8. I am also trying to use CoPilot to see what errors I find, filing bug reports when I see them. CoPilot and my research following shows a pinion degree of 5 degrees down. I am assuming this is to compensate for large power and axle wrap pulling the pinion up. At one point in my searching, I found a factory setting of ~1 to 2 down. Though I can not find it again.

My neighbor came over and looked at the setup of the 7.25 out of my 1969 barracuda (318 w/904). It showed 8 degrees pinion Up.

What the hell? A difference of 13 degrees is a huge margin of error. I am taking the assumption that I dont have enough power to worry about custom geometry due to axle wrap or setting up weird suspension configurations. I want to set the 8.8 to a-body OEM.

Now take into consideration that there is a axle center line change as the 8.8 is a larger axles shifting center line up from the leaf springs, add the mopar perches I bought, and we could be close to 1 in up resulting in the rear of car sitting 1 inch lower. Not sure how I will counter that. May use a 1 degree shim depending on the change of having 1" longer shackles in the rear to set ride height where I want it.

The pisser is, my neighbor was so sure of the 8 degree's that we burned the perches in. But my continued research is showing else wise. Where am I going wrong if my barracuda axle is correct?