I thought that's exactly what I WAS trying to do. At the axle centerline, NOT the contact patch of the tire, the upward rotation force against the pinion shaft is exactly the same as the torque applied to the axle shaft (Isaac Newton...equal and opposite reaction...???). If not, where does the "rest" of the torque disappear to? EDIT: I am not talking about driveshaft torque here. Gear reduction has nothing to do with it. If I am putting 1000 lb/ft into rotating the ring gear down, then I also have 1000 lb/ft trying to lift the pinion shaft straight up. As far as the laws of physics go, I agree 100% that they do NOT change. So why would the force (obviously tension) applied to the top link in the video suddenly reverse to "reduced compression" just because the brackets were welded to the axle instead of floating? It makes NO difference whether the suspension is a 3 link, parallel 4 link, or triangulated 4 link; the basic force coming from pinion climb is always in the same direction. How that force is applied to the CHASSIS is where I think we've come unstuck. Your original diagram with all 4 links in compression does apply to an IRS system (my words, not yours), as the pinion shaft is disconnected from the suspension linkage because there is no solid axle housing transferring the force to the brackets and links. It also applies to the OUTER links on a dirt track floater system, where (as you said) the pinion force is once again disconnected from the axle housing by the floater bearings. As soon as we weld the upper brackets to the solid axle housing (anywhere above axle centerline), the pinion climb is now resisted by the upper links. And Al, this: "Although experience is valuable, it isn't the same thing as knowledge." HAS to be the quote of the month... My "experience" in changing out pulled heim joints on the top links of race cars obviously hasn't translated into any "knowledge" of why that might have happened... I'm not being defensive, my point was that while I use Google and the internet for information, my own observations come from things that I have seen and had in my own hands. I know, for a fact, that if the upper links on a solid axle suspension run uphill to the frame, and the lowers are level, the car will squat under hard acceleration. Which is where we started, so I'm done.