After installing the front suspension, we continue our merry way to the back of the car and mount the rear end and the springs and shocks that go with it.
The front suspension, with the complexities of steering, has been completed. Now, we move to the back and put things in order there. First of all, the 2x4-inch, 10-gauge cold-rolled steel frame from StreetBeasts has been specially engineered to accept the Ford four-link rear suspension from a 1979-'94 5.0 Mustang. The really good news is that the Ford's 8.8-inch rear is a direct bolt-on and it can handle 300 horsepower, so you can load the nose with plenty of oomph! . Incidentally, the correct hub-to-hub width of the rear end is 59.5 inches, just in case you get confused while rummaging through a salvage yard while trying to save a few dollars on components. The axles from a donor car can offer either locking or non-locking differentials. Ford sway bars can be used, but the lower control arms must have provisions for it. Naturally - if you're using salvage yard parts - you'll want to inspect and repair as necessary anything that requires it in the rear end before attaching it to the frame. Of special concern will be leaking seals, dented differential cover, missing or damaged hardware and binding axles or even locked upper and lower control arms.
CAUTION - this installation will require some help from a buddy even if you're Arnold Schwarzenegger because the rearend is heavy! At the very least, you'll need a movable hydraulic floor jack to help hoist the rear end into position from the back of the car.
Once again, you'll either use the bolts from the donor car, or find Grade 8 or better bolts from a retailer you can locate by looking under "Fasteners" in your local Yellow Pages. Remember, though, that Ford has alignment bumps in the bushings for their step-shouldered bolts, and the bushings may have to be relieved to allow half-inch Grade 8 bolts to fit properly. With the differential supported on the movable jack, its bottom perhaps cushioned with an old towel, slide the whole rear end assembly under the frame. Now hold on for a second: You're going to have to raise and lower the rear end several times in the next few minutes. It's important for you to realize that the location of the flexible rear brake hose, and where it attaches to the frame, must be decided before the rear end is actually hung.
With the flexible rear brake lines attached to the rear axle, raise the axle all the way up - and then lower it all the way down to extended shock height. This shows you the full possible travel of the rear axle.
By going through these steps you can be assured that the flexible rear brake line won't be put in stress or a bind. Once this range of motion has been confirmed, you can mark the location for the brake line bracket. You can either make this bracket yourself, or buy it from Ford. Once this has been assured, you should continue with actually mounting the rear axle. Again, using a movable jack, lift the axle into position and mount the lower control arm to the brackets on the side of the frame. After installing the bolt, check the exposed threads against the thickness of the nut and allow at least a quarter of an inch of exposed threads (three threads) when it is in place. Install the washer and loosely tighten the nut. Move to the other side and repeat the process.
Here, the rearend has been raised into position on a movable hydraulic jack for a test fitting.
Cameron here attaches the lower control arms to the suspension bracket on the side of the frame. The spring is at the ready!
Instead of using the rear brake line from a donor car, Cameron opted to run a flexible hose from a bracket to the gear carrier.
UPPER CONTROL ARM INSTALLATION
The upper control arm bolts on the rear axle housing should be loosened to help you line up the upper control arms. Raise or lower the axle housing to assist in aligning the bushing. Then, the bolt should be inserted so the threads are pointing outward from the centerline of the frame. Install the washers and the nuts, but leave the nuts loosely tightened at this time. Suspension nuts should not be fully torqued down until the whole suspension has been loaded with the full weight of the finished Street Beast- otherwise there could be suspension damage. Finally, lower the jack until the rear axle is ready to hang free.
Normally, the production brake line at the rear would be mounted on the axle. The hole where it was mounted must be - in this instance - filled with a relief valve.
SPRING AND SHOCK INSTALLATION
Since we've already installed the front suspension, mounting the rear springs and shocks should be a piece of cake. Again, you may or may not need to use a spring compressor. If the car was a full production vehicle, there would be enough weight to compress a shortened spring (or one from a four- or six-cylinder car) enough to fit it as the jack was raised. But, since this is a bare frame, there is very little weight, so the spring compressor may have to come into play to fit the spring. Of course, you may want to invite a couple of your hefty friends over and they can sit on the frame as you compress the spring with the jack enough to position it. Once again, the installed shock will ultimately hold everything in place.
Here, the spring (minus a spring compressor) is moved into position for installation.
In the end - just like in the front - the shock absorber locks the spring in place.
CHANGING THE 4-LUG AXLE
While we're at the back of the frame, we might as well consider changing the four-lug axle out for the popular five-lug unit. But, please note that this is an optional procedure. And, if we weren't going to do this, we'd concentrate on running the brake and fuel lines - which will follow.
The first thing you do, after making sure the frame is mounted securely atop sturdy jack stands, is to drain the old oil out of the gear carrier. With a pan in place to catch the old oil, remove the cover bolts and the cover. It has probably been on for a long time, so you may have to use a putty knife to break the seal and expose the pinion gear and spider gears. Rotate the pinion flange rearward to make the lock pin accessible and use a six-point wrench to undo the pin from the gear hub. Now, the centering pin will slide right out of the rear axle housing so the axles can be pushed inward from the sides. At this point, remove the C-clips that hold the axles in place. Please note that the C-clips are positioned with the flat side facing outward on each side. At this point, you can pull the four-lug axles out, and replace them with five-lug units. These will slide back into the axle housing, where the C-clips will be re-installed and the centering pin will be re-inserted.
Finally, the lock pin will be put back into the mix. Here, though, you should clean the lock pin threads, and put Loctite Threadlocker on it to guarantee that it remains in place. A wobble head extension can be used with a six-point shallow socket.
Now, it's time to replace the gear carrier cover - but take a few extra minutes here to do it right so you can prevent leaking oil. First, clean the old silicone seal from the cover and the mating surface of the gear carrier, then, reapply new high temperature RTV silicone to the cover. But be warned: Don't overdo it! Otherwise, the silicone will squirt out of the cover, or worse, drip onto the gears. To help assure that you use the proper amount of silicone, start by applying it in a series of "dots" around the inside surface and where the bolt holes are located. Now, using a coarse thread bolt (and throw it away after it's been used) to smooth out the silicone. The thread pattern will provide you with row after row of sealing "gaskets". But, before you do anything else, let the silicone cure for 10 to 15 minutes before putting the gear carrier cover back on. Gently attach the cover to the carrier, and then - by alternating from side to side - gently tighten the cover finger tight. Before torquing it down to 10 to 15 pounds, let the silicone cure for a few more minutes. Oh, and there's one more important thing - don't forget to fill the carrier with 80-90 weight hypoid gear oil. Check the capacity of your rear end by looking over a factory manual, but it generally takes two one-quart containers. And, of course, once it's full, the oil will run back out the fill hole. Okay, that's enough for this installment on building a Street Beast. We'll be back next time to run the fuel and brake lines and temporarily mount the brake master cylinder.
Now, we move on to an optional procedure - changing out the four-lug axle for the more popular five-lug unit. For photographic purposes, the oil has already been drained from the gear carrier.
With the cover removed you can see the gears. Here, we undo the 5/16 lock pin from the hub with a six-point wrench.
This is the lock pin.
Now, gently slide the centering pin out of the rear axle to allow the axles to be pushed inward.
Now, from outside, push the axles inward.
Remove the C-clips from each side.
Here's a clear view of the C-clip. When it's time to re-insert them, remember that the flat side of the clips face outward on each side.
Now, you can slip out the four-lug axle, and replace it with a five-lug unit. Ford has a replacement axle that will cost you about $200.
Once the axles are in place, re-insert the centering pin.
And replace the C-clips
Now, clean the 5/16 lock pin and put Locktite on its threads.
Tighten the 5/16 lock pin. A wobble extension will work here!
Next, you've got to button up the gear carrier. But, first, the old silicone seal on the cover has to be cleaned off. The bolts should also be cleaned.
Re-apply high temperature RTV silicone to the cover. To do this properly, apply a series of silicone "dots" around the inside surface and near the bolt holes.
To help make sure you have the right amount, use a coarse thread bolt (and throw it away afterward) to smooth out the silicone.
Here's a close-up look of what happens - you get row after row of sealing "gaskets".
Before installing the cover, let the silicone cure for five to 15 minutes. That's about enough time for a cup of coffee or a cigarette. Here, the cover has a centering bolt in place.
Now, gently, place the cover on the gear carrier and tighten it just enough to hang the cover in place.
From opposite sides of the cover, install the additional bolts simply to hang the cover.
Here, the bolts are tightened by hand , again, alternating back and forth.
After letting the silicone cure for a few final minutes, tighten the bolts - again alternating from side to side.
With the cover in place, and tightened to Ford specs, you're almost done. But, it's at this point that you should renew the gear carrier oil.
Here, the fill plug has been removed from the front of the gear carrier.
Using 80-90 weight hypoid gear oil, we refill the carrier. Check the oil capacity of your rear end by looking over a factory manual.
Using Teflon tape, Cameron wraps the fill plug before re-inserting it.
