Okay, I got around to installing those full length AALs a little while back. I put together a few other bits that needed to be slapped on too. There was an ORD U-bolt flip kit and the correct stainless rear axle hardlines from Inline Tube.
I knew that my current U-bolts weren't going to be long enough with an extra 0.401” thick leaf spring on each side, so it was time to upgrade. Unfortunately, I forgot to specify that I needed longer than stock U-bolts when the kit was ordered (the short ones are in the first photo and the longer ones are shown later) but we got it all sorted out soon enough. The stainless rear axle brake lines were the last part of my brake system that hadn't yet been replaced. When I'd purchased the SS line package, it was ordered for a 1972 K10 Suburban to get the disc brake stuff positioned correctly in the front, but my rear axle is from a '71 C20 so the rear lines that came with the SCTB71B4 kit weren't even close to fitting.
Here is the original leaf spring pack, already apart and with the new leaf slid in just below the main spring. The AAL spring only had a smidgen more arch to it than the originals.
Once the center pins were back in and tightened down, the overall arch of the springs remained completely unchanged at rest. I laid one spring pack directly on top of the other just to verify, and they really were identical curves.
The old center pins themselves were a little short now, but I threw the modified spring packs back in just to see how things were shaping up. The rear did indeed raise up a good bit. It actually looked a little stink-beetly to me at first. After breaking out the angle-meter and doing some calculations, the difference in angles between the two rear driveshaft U-joints (t-case output to driveshaft, driveshaft to pinion) which had previously only been 1° was now 5.5°. I ran some more calculations and figured that a 4° shim should get the difference to 0.5°. At this height, the rear pinion and driveshaft angles were very close, almost ideal for a CV shaft. For now I'm running it in a “W” configuration. I also took a look at the front pinion angle and then ordered some shims. The cast aluminum pinion angle shims from Pro Comp looked decent when they arrived at my door, but my center pins slipped right through the hole on them. This wasn't going to leave the bottom part of the center pin sticking out far enough to easily locate the leaf springs on the perches anymore. My solution involved some handy washers from the big spare washer can. I'm not sure what they came from, but each one had a slight outside taper so that they fit tight and sat flush, and the ID was just right for the center pins to pass through.
This way the shims would be bolted to the leaf pack and it'd be much easier to get everything lined up come reassembly time. Like so:
By now I had tossed the old center pins and thrown the new ones on too. I had to get them in before bolting the shim to the Zero-Rate. While waiting for those shims to arrive I had POR-15 coated the new U-bolt plates from ORD (which have a handy, elongated slot to accommodate moving the axle backward or forward with the Zero-Rate), so as soon as those new, longer U-bolts arrived, everything was ready to go together.
Nice shiny cadmium plated bolts and less protrusion on the bottom of the axle. I also did a little paint touch-up while I was down there.
The end results over time:
Top to bottom:
4” lift springs w/ 1/2” longer shackles = 4.25” total front lift
4” rear shackle flip and 1” Zero-Rate = 5” total rear lift
4.25” total front
4” shackle flip, 1” Zero-Rate and 2” longer shackles = 6” total rear
4.25” total front
4” shackle flip, 1” Zero-Rate, 2” longer shackles and 1” - 2” Superlift AALs = 7” - 8” total rear
At least it doesn't look saggy in the rear anymore aside from the slight lens distortion the camera added. Some time spent with the tape measure on the flat part of the frame showed that near the firewall it is 23 13/16” from ground to frame and under the c-pillar is around 24 1/8”. That's not that even half an inch difference. I'm sure the rear will probably settle a bit more too, and hopefully things will stay close to level when all is said and done. Have to be careful because Utah law states that for my GVWR range the frame can't be more than 26” above flat ground. I also measured all of the rear driveshaft angles after the shims were in place, and the difference in U-joint angles is indeed 0.5° under power. No driveline vibrations to be reported.
I haven't felt a noticeable increase in ride harshness after the AAL install either. Though the ride has been a bit jouncy at slow speeds with the stiffer HD front springs, its still not bad. It does seem to have a good deal less body roll than I remember from High School. I was actually out testing in a parking lot recently, making sure there weren't any odd effects from the possibility of roll-oversteer that comes with having the rear shackle sitting lower than the front spring pivot on the rear axle. There really isn't anything out of the ordinary aside from some unrestrained items I flung around inside the cabin.
Speaking of suspension geometries and practical research, I mentioned having looked at the front pinion angle during all of this. I did indeed order some front pinion angle shims and installed them at the same time. I was only thinking of the front pinion angle when I did this though, not the caster angle. The difference from front pinion to driveshaft had been 7°. With a CV style front driveshaft, my initial reasoning was that the difference should be close to zero, so I ordered some 6° shims and threw them on.
Oddly enough, even though the rear axle changed exactly as I had predicted, the front wasn't even close. The pinion stayed at the exact same angle somehow, and only the driveshaft angle changed. The difference between the two at least decreased to 5° under power. After doing some more reading and research, I decided to check the caster angle, concerned that it might now be too little after having installed those shims. As it sits now, the front axle caster is 3.5° positive. It hasn't made any difference in handling or steering feel and the wheel still centers itself just fine after turning. It seems that the general opinion is to simply find a decent balance between pinion and caster angles unless you're willing to cut off and re-weld the axle Cs and spring perches. Another very knowledgeable individual made a nice argument for being able to run less caster angle with taller, wider tires because of some complicated calculations based on scrub angles and other influences. For now I'll keep driving it and see how things go. I can always slap in some shorter, less angled shims in the future if I want more positive caster.
The only other things I have done recently were take care of a minor coolant leak and start wiring up the 7 pin trailer plug and trailer brake controller. The front of the intake manifold was holding a nice puddle of green liquid when I was looking things over recently, so I hosed it all out and dried everything. After letting the engine run a while, a tiny drip of coolant reappeared at one of the bolts that holds the intake to the driver side cylinder head. I had to take the EGR valve off to get at it, but after cleaning the bolt up and slopping some thread sealer on it there hasn't been any more green stuff up top.
While the hose was out I'd cleaned up the dust and dirt in the engine bay, realizing that there were no pictures of the whole engine bay anywhere in my personal collection or online, just various close-ups. So here they are:
This seems to be how my builds go, the outside can stay looking crummy, all primer, rust and old body filler while the drivetrain is sorted out properly first. Then comes the interior and eventually I get around to the body work.