Owning sports cars with over 10 years of hard miles racked up comes at a price, but not a price we’re all ready for a majority of the time. We’re not talking about the initial expense, but the maintenance itself. You may not realize it at first because the deal on the car was so good, but there are a lot of areas on the car in which components will need to be replaced.

In our case, we have a 2004 E46 M3 (Project M-Track3r), and were aware that some examples had subframe mounting location issues prior to purchasing it, so we knew what we needed to tackle upon taking it to the track and adding more power. The rear subframe mounting locations on the chassis on the E46 M3 are prone to cracking under hard driving and old age, but not every E46 M3 will have this problem. There are plenty of folks out there who have reported that their rear subframe mounting locations are free and clear of cracking.

Little hairline cracks in the mounting locations of the rear subframe.

While we were checking for cracks in the subframe on our example, we managed to find a few little hairline cracks, but nothing major. To remedy this, we ordered a subframe reinforcement kit, and while we were at it, decided to replace all of the subframe, differential, and control arm bushings to get Project M-Track3r handling just like the day it drove off of the showroom floor (minus the Bilstein Clubsport coilovers).


The rear subframe reinforcement plates, rear shock tower reinforcements, subframe bushings, and differential carrier bushings.

The E46 rear subframe reinforcement kit includes four CNC-cut plates that weld to the locations on the chassis that accepts the rear subframe. While we were at it, we ordered polyurethane subframe and differential carrier bushings. The polyurethane bushings are a great upgrade from the worn-out rubber factory bushings that were in the car since it rolled off of the production line. We also ordered the rear shock tower reinforcement plates as well. Why not cover all of our bases, right?

The full set of control arm bushings Whiteline sent us, as well as the front sway bar end links that we will be installing at a later date.

Speaking of covering all bases, Whiteline supplied us with a full set of control arm bushings in addition to the subframe and differential bushings we received along with the reinforcement kit. Whiteline also included some adjustable front sway bar end links, which we are going to install when we tackle the front suspension at a later date. With our subframe reinforcement kit and bushings all in the same place, we removed the rear subframe from the car and set to work.

From left to right: lowering the subframe, tacking the reinforcement plates, and the plates fully welded and painted.

With the rear subframe out of the car, it was easy to access all of the bushings, but first, we decided to install the subframe reinforcements. After mocking them up in their locations, we grinded down the areas to prepare for welding. Once the areas were prepped, our shop tech, Dean, tacked the plates in place and then welded them to the chassis. After the subframe reinforcement plates were installed, we installed the rear shock tower reinforcement plates using the same procedure. Unless you are experienced welder, we would recommend taking your E46 to a shop to have the subframe reinforcements installed. It’s a lot to undertake at home, especially with welding involved, which potentially ups the possibility of a fire.


From left to right: the differential carrier bushing being pressed out, and the new bushing installed.

With the subframe reinforcement plates welded in and painted to prevent them from rusting, we got crackin’ on the bushings. The factory subframe bushings were pretty easy to get out, but the differential carrier bushings were a little on the tougher side. Using a ball joint/bushing press, we were able to free the factory bushings from their locations and press the new polyurethane bushings in.

To install the Whiteline control arm bushings, we removed arms from the subframe for easier access and pressed the bearings out. The bushings went in with virtually no problems, and we were very pleased. Some bushings were quite the pain to press out, but having the subframe out of the car made the whole operation a lot easier.

Whiteline has all the control arm bushings you need for a full overhaul.

After we pressed all of the new bushings in, we reinstalled the suspension components back onto the subframe, which was strapped to our transmission jack, and lifted the subframe back up into the rear of the car and secured it to its newly-reinforced mounting locations.

With the subframe reinforcements and bushings, differential carrier bushings, and Whiteline control arm bushings all installed, we got the car rear of the car back together and checked everything one last time before putting the wheels and tires on.

We were very pleased with the how easy the Whiteline bushings were to install, and we can’t wait to get Project M-Track3r out on the track to feel how tight the rear of the car feels, compared to before the bushings were installed. Stay tuned for results of how Project M-Track3r performs out on the track!