Opened Up The Old 489

You need to measure the clearance into the bottom of the cone receivers, so you don't have to pull it out again soon. I do this with electronic solder, you know, the thin stuff. I snip off two pieces about 1/2 inch long and lay them in the bottom where the cones come down. Then I put the cones in there, and with a big brass drift (pirated from an old graintruck rear), a beat down on it a couple of whacks. Then I pull the cone out, retrieve the solder, and measure how flat it got pounded.I am looking for the solder to be .080 or thicker. If it's down at under .040, I machine the face off the cones to get the .080 that I am after, for a long operating life.
To get back the spring preload, I get me some side-gear washers from the Ford dealer, and stuff one in each side. Later after it's all prelubed with the special recipe of oil and additive, I measure the breakaway torque and turning torque.
The turning torque that I have found acceptable on the street with my 367, is 120 ftlbs minimum. I adjust that with those side-gear shims, until I get it. This works well with my 295s and also with my 325/50-15 BFG-DRs . 120# is too tight for 245s, and I think almost borderline too tight for 275s
If you set up at 130, it will skid the inside tire on every Part-Throttle turn, so basically acting like a spool.
Down at 100 ftlbs, it will often shift torque left to right and back as the traction, and power input changes. I think the sweetspot on the street is 115 to 125, so that is where I set all mine. And remember this is with the Whale-oil additive, prelube recipe installed where it needs to be.
It will read different without the whale-oil, and also different with synthetic, so I cannot speak to other concoctions.