60-66 Rear Axle Swap to 73-87 Rear Axle & Pinion Angle
 

I'm swapping out the 12 bolt 3.73 axle on my 65 to a 3.07 12 bolt from a 77. I've ground off the old perches and have set the new axle on the trailing arms. I've done a bunch of research on setting the pinion angle and wanted to confirm some things before I weld them up since this is my first go round on doing this.

Here's some more detail. I plan on swapping out the two piece shaft for a one piece. I'm dropping the front with 2-1/2" drop spindles and 2" drop springs. I'm also dropping the rear with 3" drop springs. I currently have the motor/tranny mocked up and the angle on at the tranny is -3.5*. From my understanding the angle on the pinion yolk should then be +3.5* but not in line with the tranny, just parallel. Also, I've read on several threads that the pinion angle on a truck with leaf springs can change upwards of +2* under torque, but I only found one comment on a coil spring/trailing arm thread that stated the flex is only +.5*. Taking this into account should I set my pinion angle at +3* to account for the +.5*? Also, can someone confirm that the +/- range between the two angles can be 1* to 3*?

One caveat, this is all currently without load which I intend on adding, but wanted to make sure my understanding of setting the angle is right.

Thanks!

Re: 60-66 Rear Axle Swap to 73-87 Rear Axle & Pinion Angle
 

When I swapped axles in my 72 I located the perches one at a time, letting the existing perch hold the axle angle while the the u-bolt located the new perch. I then tack welded the new perch and let it locate the opposite new perch. I dropped the rear 4" using springs only and have had excellent results with no vibration at all. I did this on a LWB truck and simply used a bent panhard bar to center the axle. I race and show this truck as well as drive it locally. After much research I retained the two piece drive line as they are more forgiving especially when big block torque and horsepower are being used to turn a 12-bolt 4:56 posi with 15 X 30" Sportsman Pro's. Your set up should work well as long as that one piece drive shaft is balanced and balanced for highway speeds. That entails a thick wall DOM tube of at least 3" diameter. As long as the pinion angle is within 3 degrees of the tranny output shaft you should be good. The trailing arm suspension (pinion angle) doesn't change hardly at all under torque but will change with load and as the suspension travels...Here's a video of mine heating the hides up, watch the rear end... https://youtu.be/_jXxaOqm36M?t=1m16s

Re: 60-66 Rear Axle Swap to 73-87 Rear Axle & Pinion Angle
 

Thanks, mine won't have quite as much torque at take off, lol. Running a 350 4-bolt with Vortec heads and 650cfm 4bbl but matching it with an M23 4spd with a 2.98 first ratio so that I can launch the 3.07 rear and get some mileage. Mostly plan on cruising. I just don't want to cruise and shake at the same time.