Got the on-board-air compressor hoses made and installed. The compressor works great, and with the hand throttle with the engine setting at ~2K rpm, it supplies plenty of air. Leaks down from about 115 psi to 90 in about two hours, so I have a small leak some place. I still need to install the arming switch and wire (will change to a power rather than grounding wire), as well as getting a inlet air filter.
Picked up a Ford 8.8 rear axle out of a 1998 Ford Explorer. It's outfitted with 3.73 LS gears, (code D4, a 3200# disc brake axle). I started stripping it, and opened up the case, and found the usual black stinky gear oil. No water, and not looking too bad inside. The gears all look good. There is however 0.050 in ring gear backlash (spec is 0.008-0.015), and about .012 in pinion fore aft play. Feels like almost no pinion bearing preload, so with the end play, I'll have to re-torque the pinion flange bolt. I'll also have to re-shim the ring gear to get it's backlash within specification. The limited slip clutches seems to be good and tight.
Now to some decisions and parts planning. I'll by new rotors, pads, calipers, hoses, etc... ( new proportioning vale and improved master cylinder) as well as of course clean and paint everything. I'll also cut off the old spring perches, as I'll need to realign them in both width and rotation to get the proper pinion angle. With staying with a spring under suspension, and not having to use pinion alignment shims, I'll only loose about 1/8" in rear height with the larger diameter axle tubes on the 8.8.
The question is, why 3.73's, why not 4.10's? My thoughts are with the automatic, and a 4.6L engine producing ~240 HP & 315 ft.lbs. of torque (33% more HP & 43% more Torque than stock) I should have plenty of power and torque multiplication. The stock YJ with 3.07 gears and tires (215/75R15) ran with a crawl ration of 20.46:1 and at 55MPH the engine was turning about 2,048RPM. With the 3.73's and the 33" tires, the crawl ration will be 24.86:1 and at 55MPH the engine would be spinning about 2,088RPM. So even without all my extra power I'll have a little better crawl ratio and slightly higher engine RPM. With a torque converter multiplier of 2 (single stator TC), my crawl ration would be 49.72 to compare to a manual setup. I've seen people say the best ration from as low as 50, to as high as 85, with a few wanting 100 or higher. My M has a ratio of 76.3:1. 4.1 gears would only give me a craw ratio of 27.32:1, while s3.73's with a 4:1 transfer case would yield 36.55:1 (very close to the effective ratio of my M).
So my thought is to stay with the 3.73's and if I need a slower crawl ratio, upgrade to a 4:1 low range transfer case. I'll also be looking to install a new set of 2" lift springs to give myself a little more ground clearance, I already have a 1" body, and 1/2" in boomerang shackles as well as liberal wheel well openings. I may even stretch the rear axle back about 1" with the new axle spring perches.