Before reassembling the rear subframe on a Spec E46, you must weld in a rear subframe reinforcement kit. I sourced mine from Condor Speed Shop. I don’t own a welder but we all know someone who either is a welder or has a welder. My neighbor has a MIG welder he agreed to loan to me if I helped him remove and install a 454 in his 1970 pickup. Seems fair.
Since the car is unmovable, I can’t just take it to a shop to have the welding done. I would need had to have done that while the car was still intact. The added labor charge for removal of the rear subframe and gas tank would not have been cheap. Otherwise my option would be to call a mobile welder to come to my house and finish the job for me. If this was your option, do yourself a favor and prep the area to be welded so all the welder has to do is show up and weld. The quicker you get them in out, the cheaper it will cost you for the job. If they have to remove components, and prep the areas that need to be welded, it’s going to cost more.
The chassis mounting points on the E46 chassis are prone to cracking. It’s a flaw in the manufacturing process that was known by the factory, but left as is. The metal in these areas are known to crack and eventually fail. The Condor kit is comprised of six laser-cut pieces of 14 gauge sheet metal that need to be welded into place to strengthen, and effectively double the thickness area and spread the loads into the chassis better. These cracks do show up on street cars, so part of the process of removing the paint in preparation for welding is inspecting the metal closely for any signs of cracks. You cannot always see the cracks through the paint!
My chassis was in perfect condition, so it didn’t take much time with a flapper wheel to remove the paint to bare metal. If you find cracks, one method to stop the crack is to drill a small hole at each end of the crack. This helps prevent any future spread of the crack. Then do a quick welding of the crack, followed up by grinding it flush to complete the repair. Unlike most repair kits I’ve seen for the E46, the Condor kit includes an additional pair of square plates that allow additional welding to be done from above inside the trunk in a place where the factory spot welds are located. These panels cover up the hole you must cut into the sheet metal to do the final chassis welding under the floor, before you weld up the plates on the interior floor to cover up the access holes you must create.
Welding Tips
The metal on the car in these stamped areas is thinner than the 14 gauge reinforcement plates. It’s too easy to blow holes in thin metal with a decent welder. So the technique I resorted to was to start your weld on the plate, drag the puddle to the sheet metal, then quickly back to the plate. One has to move quick and not dawdle on the chassis sheet metal very long. I blew a few holes, which I had to go back and fill in with a few tack welds.
Overhead welding is horrible. I had on a welding helmet, with a face mask, and a hat on with full welding leathers and gloves. Somehow I was able to launch a spark into my left ear. I could hear it furiously burning through my cloth face mask that was covering my ears, and drop into my ear, giving all of the little hairs in my ear a quick fiery death. I wish I had video. It was quite a dance. This happened three different times. So much fun.
I was able to fully weld in the plates and tack weld in the two spacers that the instructions say to glue in with silicone. Then I ground the welds flush with the mating surface where the subframe bushings would live. If you leave the weld valleys and peaks in place, it could dramatically impact the way the subframe sits in the car and their potential effect on the bushings that sit on them. After grinding, what’s left is the welds along the sides of the plates. Once I was happy with the way it all looked, I sprayed some rust preventative primer on top of everything and finished it with a couple layers of undercoating.
While all of that was drying, I tackled part of the fuel system that was bothersome. The stock gas cap is fine, but the filler neck has a factory restrictor inside that sandwiches into the filler neck. With the tank out of the way, a few small fasteners and a vent hose is all that’s needed disconnect to drop the filler neck out of the car. There are four small tabs that crimp down and hold the filler neck together. Using a small screwdriver, I bent the tabs out and wrangled the filler off of the pipe, then I slid the restrictor piece off and out of the pipe. Now I can use a 2-inch fuel filler hose. It’s not like I will ever need to fill the car quickly, although a faster filling tank is way more desirable than a four minutes plus holding a 5-gallon jug up in the air waiting for it to drain into the tank. Also, with the stock restrictor, you had to hold that little door open for it to fuel.
Before I reinstalled the subframe, I had to put the gas tank back in and connect all the vent lines and fuel lines. I refurbished the subframe with all new Condor Delrin bushings, and it was sitting and ready to go in. I didn’t assemble all of the control arms and the differential on the subframe and install it all at once because I thought that if the metal inserts on the front subframe bushing might bind up it could make for an impossible reinstallation.
I did have to use a soft mallet to persuade it up and over the studs. Getting the alignment right was key and the front two nuts went on easily and the two rear bolts also were compliant and tightened down easily.
Then I moved onto the upper and lower control arms. I did mark them left and right so I couldn’t screw that up. One thing to note, if you install the differential, it’s impossible to install the driver side upper control arm bolt on the subframe. I’m glad I waited to install the differential until after I installed the control arms. As I mentioned earlier in this story, I chose the Ground Control adjustable lower control arms for this build. It’s easy to adjust without having to disconnect them, compared to other aftermarket lower control arms, and gives me the confidence they’re not going to fail.
The differential is awkward to install. I tried to put it on a floor jack, but at the end of the day, it needs to go in with the pinion shaft facing upward in the air and rotate the rear of the differential up once the front is in place. It’s just awkward and has to be muscled into place. I was able to hold it in place and get one of the two front bolts started, but barely. The Delrin bushings require precise alignment for the two front bolts to go in correctly. Once I got one started, I installed the rear bolt to hold up the back of the beefy differential. Assembly required a precise location of the differential in the subframe for the mounting hardware. It is easy to cross-thread the bolts, so take your time.
Then I reinstalled the driveshaft to the differential. The last item to install in front of the driveshaft is the aluminum piece that goes over the two main studs on the subframe and also bolts up using the two spacers in the Condor reinforcement kit that was recommended to glue in place using silicone. I figure why not just tack-weld them in place? I didn’t need to weld them in completely and if the bracket comes off, the chances of losing the spacers is minimized by them being permanently affixed. That’s how and why I did it.
The last major components remaining to be installed are the trailing arms. I had left the axles in them, mostly because I was lazy and I wanted to see if I could do it. I put the floor jack under the middle of the trailing arm to hold it in place and got the mount into the body and managed to get a single bolt started. Then I attached the upper and lower control arms. This not only centered everything up, but helped to locate the other two bolts. The last step was to install the axle shafts to the differential, which was quick and easy.
Then the new Zimmermann brake rotors and calipers loaded with PFC brake pads. The new brass guides and pins went back on easily. In fact, I installed the brass guides in the calipers a while ago then I set them aside. The new ABS sensors went in and were plugged into the connector and resealed. The last thing to do was install the brake lines and the wheel studs. It all came together nicely.
