Jeep Cherokee Ford 8.8 Rear Axle Swap - Project Ain't It GranderPosted in Project Vehicles on March 1, 2008 Comment (0)
Last month, we presented T&T Customs' very nice long-arm suspension system, and we then headed off to Moab where we gave it a "trial by trail" evaluation.
It passed-in fact, it did better than we anticipated. The front axle needed to be shifted a bit to the left to center it, and more caster angle added to improve pavement tracking, but otherwise we were pretty dead on. Low-speed wheel articulation was outstanding, even with our Addco sway bars hooked up. However, after three days of trails, the stiffener bar overloaded our connecting links, and they bent into snakelike shapes to the point where they had to be disconnected for the remainder of our week. (Yes, we have since replaced them with some new stronger tubular ones.) Dry sandy washes and dirt roads were a flat-out blast to run at speed as there was just the proper amount of tail-end oversteer to let us power through a controlled drift.
We're still working on some pavement tracking and roll steer issues that hopefully we will soon solve. We will be sure to give you a year-end update on our final conclusions.
Something to keep in mind is that the long-arm kit from T&T Customs is at the top end of suspension systems in quality, ride quality, usability and, unfortunately, price. This is not the suspension for the guy who just wants to raise his vehicle to obtain the "cool off-road-ready" look. It's designed for the hard-core user who wants the very best. The detail and precision of all the bracketry is, in a single word, outstanding. Professional welding skills are definitely needed to do the installation.
Now, let's jump back a few months to the drivetrain modifications and start with the rear axle. We weren't quite sure what we wanted to do in the rear. Yes, the Grand came equipped with a Dana 44. But here was the problem: it's a hybrid 44 with an aluminum centersection, weak axletubes, C-clip drive axles, and no aftermarket support. Only two gear ratios are offered: 3.54:1 and 3.73:1. Ours had the 3.73:1s because of the trailer towing package, which would be marginal with our planned 33-inch-tall tires.
We did have a Scout Dana 44 stashed away that we at first considered using, but it had drum brakes and a 5-on-51/2 bolt pattern. Yes, we could have converted it to a 5-on-41/2 bolt pattern and even added disc brakes, and perhaps that is what we should have done, as in the end the overall price would have been less.
Instead we went with a '95-and-later Ford Explorer 8.8-inch rearend. We got the disc brakes, the same ones used in a lot of aftermarket conversion kits, a slightly larger ring gear (8.8 versus 8.5 inches), and 31-spline axles (that still had C-clips for retention).
The drawback with this axle is that it was about 1.25 inches narrower than the ZJ's original. To bring the track width back out, we located some billet-aluminum spacers in Jegs' catalog that centered on the axle hub, not on the lug studs. That also meant longer studs for proper nut engagement, and Moroso had the ones we needed. Then we had to drill out the stud holes in our stock axleshaft flanges a bit for a proper pressed fit. Actually, just after we did this, Alloy USA shipped us some very nice replacement axleshafts made from double heat-treated 4340 chromoly material that carry a 10-year warranty against breakage. While still a C-clip design, with our present tire and motor combination, we are confident that we will never break them.
The axle flanges were drilled and tapped for either the 5-on-51/2 or the 5-on-41/2 bolt pattern. The supplied screw-in studs weren't long enough to use with the spacers, so some Moroso stud/bolts were used. However, upon installation, we found the heads hit the emergency brake, and we ended up hand-grinding the head a considerable amount for proper clearance and using a red stud locker to make sure they would not back out.
But again, I'm getting ahead of myself here. Let's go back to the bare axlehousing. All the leaf-spring brackets were cut off and the welds ground smooth. We figured the bottom design of the pumpkin was a rock catcher, so we bent up a 9/16-inch slider and welded it on. Yep, we know, you're not supposed to weld to a casting, but we did anyway. With a large acetylene torch tip, we first heated up the housing to the point where it was uncomfortable to touch with a bare hand, and then with our wire feed, we welded on the skidplate in several locations. While we were at it, we ran some short beads in the area where the axletubes join the pumpkin, as the 8.8 is notorious for spinning the tubes. We then wrapped everything in some fiberglass insulation and let it cool slowly.
When Bob Levenhagen from T&T Customs arrived at the shop, the housing was ready for him to install the axle truss that also served as an upper-suspension control-arm mount. With the pinion angle set at 15 degrees, custom coil buckets and shock mounts were set level and welded on. Also installed at this time were the upper and lower control-arm mounts, shock and sway-bar brackets, and some bumpstop plates (that later came off in a design change as shown last month).
We selected Motive Gears in a 4.10:1 ratio, along with its bearing kit, to install with our Eaton E-Locker. We have had excellent results with Motive Gears in the past and expect the same with these. Our gear contact pattern wasn't perfect, but well within an acceptable range.
Why the relatively new-on-the-market electric locker instead of a proven Detroit Locker? Street driveability on icy roads, along with (at that time) a full-time four-wheel-drive system. We talked this over with West Coast Eaton representative Scott Frary, and he convinced us to go this route. This gave us a standard open differential and-when we needed it-a totally locked rearend. It doesn't take cables or air lines and a compressor, but just a simple few wires and a pushbutton. It's not necessary to come to a complete stop to engage, but wheel speeds must be within 50 rpm of each other. So far, we don't have any complaints to pass on to him about the locker's operation.
We used the stock 8.8 cover, but added a Superlift Rock Ring to protect the ring gear and to add a bit of strength to the housing. Rebuilt rear calipers from our local auto parts store, along with turned stock rotors, provided brakes. An aftermarket steel braided hose for a lifted YJ connected the new hard lines we ran along the truss to some rubber lines that connected to the calipers.
For a driveshaft, we looked up one of the oldest custom driveshaft companies around, J.E. Reel Driveshafts, and sent them our measurements. We got back a nicely balanced shaft with a new slip yoke and equipped with the waterproof U-joints. These U-joints use a forged body that is cryogenic treated and claimed to be 40 percent stronger than an OEM joint, backed by a "U break it, we replace it" guarantee. Note we said "slip yoke." We found that the longer wheelbase of the ZJ, versus the XJ, didn't require a slip-yoke eliminator kit. Yes, we cycled the suspension through a complete shock extension numerous times with no binding. The transfer case is mounted at the original height. The suspension is set up to use every bit of the shocks' 10 inches of travel.
We played around with the sway bar and its mounting location quite a bit before we were finally happy with it as explained in Part 2. Addco was nice enough to work with us on this, and bent us a custom bar. We tried several different lengths of connecting links and finally ended up with some adjustable tubular ones from Teraflex. One of the last things we did was hook up the E-brake cables and, to our surprise, the ZJ cables were a direct hookup to the Ford rearend's brakes.
Next month, we'll cover the front axle, steering, and such where lots of modifications were made.