1996 Jeep Grand Cherokee Suspension - Project Ain't It GranderPosted in Project Vehicles on February 1, 2008
As we mentioned last month, we had decided to go with the folks at T&T Customs for the suspension on the Grand because we had seen some of their work and were impressed. Bob Levenhagen, the chief designer, wanted us to come to their Cheyenne, Wyoming, shop and let them do the installation. But we finally decided that Bob would drive over here (Montana) with the parts and pieces and do the install at our shop. This made it a lot easier on us not having to haul a whole bunch of stuff to Wyoming, such as the front and rear ends and tires and wheels.
When he arrived, we had the Grand Cherokee stripped of all running gear and up on end lift jacks. While it made welding on some of the brackets a bit more difficult than being on a lift, the arms of the lift would have interfered with installing the chassis stiffeners. Just what are chassis stiffeners? As we all know, the ZJ uses what is called unibody construction where the framerails, often referred to as a "subframe," are part of the body and made of stamped and formed sheetmetal. This all works out just fine for highway use, and most off-highway use, but when you get into some serious four-wheeling, well, the body kind of flexes. This leads to cracks around the door pillars and other places that are not desirable. The chassis stiffeners greatly improve or, should we say, prevent this body movement.
Bob's first order of attack was to clean off the subframe rails of all the undercoating and paint-a very nasty job-and to torch off the factory suspension mounts. These don't have to be removed if you're only using the chassis stiffeners with most short-arm lift kits, but they must be removed for the T&T long-arm suspension kit. The chassis stiffeners are best described as a long piece of angle-bent steel with notches cut in the vertical sides to allow conformation to the unibody's subframe. They are held up against the subframe with the bolted-on factory crossmember and then bent into the proper position with a floor- or bottle jack before being welded in place. Keep in mind, you're welding 3/16-inch (7-gauge) metal of the chassis stiffeners to about 1/16-inch (14- to 16- gauge) unibody metal. Let me stress right now that your welding skills better be up to the job, as it is quite difficult. If there is any doubt to your skills, stop now and have a professional welder do the work for you; if it is done improperly, irreparable damage can be done. Bob turned out some of the nicest welds I have ever seen.
Next step was to start on the mounting locations for the control arms. I won't go into any real detail here, as you will see as you read on. The control arms are over twice the length of the original factory stamped arms and made of DOM steel with the uppers being 1.50 inches in diameter and a full 1/4-inch thick, with the lowers being 1.75 inches in diameter and 1/4-inch thick. The axle mounting end has high-density rubber bushings to absorb vibrations, and the frame-mounted end uses a custom high-angularity swivel joint that will provide 60 degrees of total movement and is adjustable for wear, as well as being rebuildable.
While our prototype suspension worked great on the trail, with Rusty's 4.5-inch lift springs, we weren't quite happy with the high-speed handling characteristics on the highway, a pretty common complaint when a rear track bar is not used. We replaced the stock sway bar up front with a larger Addco unit and felt a definite improvement. At the rear, at first we modified the original factory bar to work with the Explorer rear end, but it didn't offer enough roll control. Our next step was to modify an Addco bar by putting it into the press and putting a slight bend in the middle to pull the outside edges in about 1 inch so they would clear the tires. This is because the Ford Explorer 8.8-inch rear end we're using is about 1 1/4 inches narrower than the original Dana rear end and would rub the tires, even with our M/T wheels having 3.5 inches of backspacing. Addco was a bit worried that our cold bend to the bar may lead to some fatigue problems, so they bent up and shipped us a new bar to match our modified one. For connecting links, we used some from Teraflex and built some U-shaped brackets to mount them both on the sway bar and the axle. We also moved the sway-bar mounting location about 1 inch forward for more spring clearance. Yes, it's a lot of work, but it paid off in much better handling. T&T Customs figured what we did was way too much work, and has now found that a TJ sway bar will work with very little modifications.
We then changed out the original Rusty's rear coil springs for new ones (PN ROR404) that were slightly shorter than what we originally used, but a larger wire diameter. This gave us a higher spring rate, and while they were shorter, they actually raised the rear about 1 inch higher. Up front, we used a Rusty's number ROR508, which was just about perfect with our heavy ARB front bumper and Warn winch. These changes in spring and sway bars made for an improvement in the "comfort" level of driving, but there still was a bit too much roll steer to totally please us.
With Easter Jeep Safari just a few weeks away, we thought we were ready-that is, until the full-time transfer case decided to start making all sorts of noises. Decision time. We finally decided to swap for an NV231 unit. Our local shop, Jeff's Off Road in Missoula, Montana, made a phone call to All Transmission Parts in Portland, Oregon, and a rebuilt 231 was shipped the next day. But just no ordinary 231, as this one had a six-gear planetary instead of the normal three-gear one, and a much wider drivechain. In essence, a 242 in a 231 case. It only took Jeff a couple of hours to make the swap, and our new Reel driveshafts were back in place.
The only problem that we encountered was with the shift linkage. Luckily, Jeff had a salvaged XJ in the back from which we were able to use the shift rod plate that connected the shift lever rod to the transfer case to solve the problem. The speedometer and the electrical plug went right into place. All the way forward on the shift lever is 2-Hi, one notch back is 4-Hi, and then Neutral and 4-Lo to the far rear. Interesting thing is that the "Lo" light comes on when in high-range, but that's OK by us.
Bob Levenhagen was also not happy with our report on handling, so he started making plans for more design modifications and insisted that we update our suspension. The week before the start of Easter Jeep Safari at Moab, we loaded "Ain't It Grander" on the trailer and headed to the Cheyenne facility. Within an hour of our arrival, the Grand was on the rack, and Mike DePalma lit off his torch and started removing the first-generation kit's lower control-arm mounts that were welded to the chassis stiffeners, while Jason, Bob's son, was busy assembling the new control arms and related parts.
By the end of the day-yes, a day that extended into the night-a new front crossmember that located the front lower control arms parallel with the upper arms and a new rear crossmember that mounted the rear lower control arms at a much greater triangulation angle, were in place along with a center-mounted skidplate. With this new design, access to the transfer case is available without removing the control arms.
On day two, the lower control-arm mounts on the rear axle were cut off, and newly designed ones that offered better ground clearance were installed. The axle-end shock mounts also went the way of the "hot wrench." The new shock mounts offered more clearance around brake calipers, as well as slightly more wheel travel. New forward-offset lower coil-spring pads were installed that allowed us to move the axle rearward without having a rearward slant to the coil spring. The geometric design of the new control arms, plus having more triangulation, will eliminate just about any rear axle roll or rearward walk. The rear is an opposite triangulated setup, with the upper bars coming off the top of the axle truss at the center mounting and going forward to the far outside of the unibody. The lower arms are mounted to the outside ends of the axletubes and near the center of the rear crossmember.
The front is a parallel four-bar setup with some pretty fancy bends in it to offer more ground clearance as well as clearing the front driveshaft and exhaust headers. It uses the original factory axle mounts and the new front crossmember.
Mike and Bob also had to redo the exhaust system for proper clearance (an exhaust system option will be available with the T&T kit). With the arms adjusted for proper caster angle up front, pinion angle at the rear, the thrust line centered, and axle set back equal, we were ready to head out the next morning.
But wait, a major snowstorm had rolled in, shutting down most of the area's roads as well as the Interstate. Not being able to leave for at least another day, we decided to make a few more modifications.
At the rear axle, the factory-located upper bumpstops with Teraflex extension blocks were eliminated and the axle pads cut off. A new style that T&T Customs had designed was pulled off the shelf. These mount within the coil, similarly to the ones on the front. By doing this, we were able to maintain the same amount of articulation and direct compression travel. The benefit was that the spring could now fall out of the upper mount during full droop, but the inside bumpstop mount would direct the coil back to the proper mounting location on the unibody.
While his crew was working on the rear, I went up front, took off the front skidplate I had built earlier and had Bob punch some 1 1/2-inch holes in it. We then dimpled these. The inward flare greatly strengthened the flat metal surface, allows some better air flow, and well ... looks cool.
On went the shocks-a set of Rancho 9000XLs to try (we are also trying out both some 5100 and 5150 Bilstein shocks), all the nuts and bolts were given a once-over, out came the rattle can for a quick paint job, the rack was lowered, the Jeep driven out of the shop for a fast trip around the block, and yes, everything seemed to work perfect. On the trailer it went, and we headed for Moab the next morning.
How did it all work out? We'll let you know in the following months, as well as going into a bit more detail on the front and rear axles, steering and track-bar mount, as well as some of the other stuff we installed.