Last time, we sourced and installed a limited slip differential in our `91 318is. Truth be told, both the last update and this one were happening concurrently, so it’s high-time we get you up to speed.
With the Eastwood Chassis Black paint dry, it was time to reassemble our front and rear subframes.
At the rear, the first step is to install any and all bushings. As we’ve stated before, we’re using polyurethane bushings from Powerflex. The rear subframe has mounting bushings that are easily pressed into place. The trailing arm bushings need to be installed and then assembly can begin. We determined our rear wheel bearings were still in excellent shape, so we did not replace these.
From there, we bolted the trailing arms in place, installed the limited-slip differential, and then installed rebuilt half-shaft assemblies. With the springs set in place, their spring pads, and the dampers mounted onto the car’s body, we were ready to reinstall the relatively simple E30 BMW rear subframe.
Up front, we installed the bushings at the rear of the control arms and bolted the steering rack back in. We opted to not install the brakes at this point, as they would only add unnecessary weight. We would later replace the steering rack with a quicker rack from a BMW Z3, but that is a later chapter in this story. Obviously, this modification would have been much easier with the front subframe out and on the bench, but we live and learn.
We then used an engine crane to lower the engine and transmission onto the front subframe, which itself was on a heavy, movable work table that we have used for years to build projects. While this process was not difficult, it did take a couple of guys and 4” wooden blocks to raise the subframe off the table enough for the engine’s oil pan to clear the table. Next, we positioned the table underneath the body—which was still on our lift—and lowered the car’s body down onto the front subframe, complete with engine and transmission. We then needed to line the subframe bolts with the body and the upper strut mounts and locate the control arms. Fun fact: there are surprisingly few points of contact holding an entire E30 BMW front subframe to the unibody.
While our reassembly method might seem a bit odd, it is how the car was assembled originally. The factory workers were onto something, as it’s a very easy way to install everything at once. Assuming you have the right equipment, of course.
With the front buttoned up, we set about raising the rear’s fully assembled subframe—again minus the brakes—on a transmission jack. The subframe mounts fought us a bit, but we were able to wiggle the bolts through the body. We then bolted the differential to the body through its new Powerflex mount. From there we could bolt the rear dampers on, install the brakes and brake lines and, just like that, we had a rather complete car again.
Next time, we’ll install the rest of the polyurethane suspension bushings from Powerflex.
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