Originally Posted by UPandComing
Ok i have a question, looking at your image posted here im seeing the pinion can be placed in a -3* position which is more angled towards the ground. What kind of set up would require something like that, iv never had to get into 4 links or ride heights YET but knowlege is power. I know when i see jacked up trucks their pinions a angled very steep to meet with the tail shaft. I dunno im just trying to get an underatanding for this being i stumbled accross the thread
Well I will try to answer this from what I remember, but I have not touched a 4-link in almost 40 years. How they set them up now, could be way different than back when I did it. Pro Stock was a new class, and there have been many changes.
You could run the pinion at that angle as the 4-link system did have mounting holes that low, but I don't really know why you would want to, because of the way the car would drive, or better yet the way the car would be pushed.
With a 4-link, you look at the 4 bars as pushers, so it is where to push the car is what you are trying to find out with your practice runs. this of course is decided by traction.
you set your bars up, now they are in the holes that they were in the last time you ran at that track, if you have not run there before you go from your neutral point. the bars are a little bit up or a little bit down, now if you could run a string from each bar end and go forward, those strings will cross, both sides should be in the same spot, side by side. where those string cross is where you are going to push on the car, if they are set right they should be straight ahead in front of the car, now you have a starting point.
From there you can set the bars to push the nose into the ground, or stand the car on it's back bumper, which I did once, before we had wheelie bars, not pretty.
Once you put your bars where you want them, each bar has two heim joints with long threaded ends and lock nuts this is when you set the pinion angle, you turn each bar the same, once set and you lock the nuts, you should be able to grab the bars and wiggle them or turn them a little back and forth, if you can't the bars were not turned the same and your rearend is not straight. It won't be off by much, but it is off.
You set these as close as you can, as you dump the clutch at 9000 RPM, you can't have them off at those RPMs.
A 4X4 with the steep angles will work, but it is very hard on u-joints. They will turn easy until you get to the biggest part of the bend or angle and it will loop over it. I have seen it in steering columns, when they put too big a angle in the u-joint on the shaft, you can't help but notice it.
Like I said I hope this still applies, I don't really know how much it has changed, I'm sure someone will correct me if I'm wrong. I think the basics are still there.