August 2003: Part 2 - Rear Suspension From The Ground Up

Back to PART 1: Gas Tank Rebuilding

The suspension will be clean and better than new when I get done! As you have read previously on my site, Rob at 2002 Haus has been advising/assisting me with this project. The front and rear suspension has been a topic of discussion for about 2 years with he and I. I have driven his 74' tii with liked what was used, so consider the suspension setup I use as part of the "recipe book" he uses with regards to "what BMW parts" and "what aftermarket parts" work best together to enhance the overall handling, performance and longevity of the car. I'm also acting as test bed for Rob's specialty powder coating services for some of the restoration you will see here. (He has more on his web site, but it's good to see them on a car. If you have a need, he can probably take care of it, just call!)

NOTE: Even if you're not going to the extreme I am, it's good to replace bolts which will be put under load by the everyday use of the car with new ones. There are also bolts which are harder than the original which are an upgrade. This hardness is measured in Grades. Grades 10 or 12 components supercede the strength of most bolts supplied by BMW originally in the suspension, front and rear. I found that large True Value hardware stores and specialty companies like Fastenal provide what you need, and if you are a stickler, you can also get exact plating color bolts from Wurth USA. but expect to pay more.

Back in June of 2002, when the tub was completely media blasted I left major components such as the sub frames to have the same work done to them. What you see below is a BMW 2002 rear sub frame, completely sand blasted and then coated with POR-15 Rust Preventative black suspension paint.
Close up view showing the end of the rear sub frame which houses the carrier bushing (L), trailing arm (Mid) and sway bar clip (R).
Top View of the same.
Underneath the middle section of the sub frame is where the rear differential is mounted.
New carrier bushings. These are held in place by 17MM bolts. Make sure and insert both bolts together, you cannot install them individually.
These nuts should be torqued on in accordance to the shop manual.
After applying the proper torque, I felt the original bolts, grade 8.8 which I had re-plated were inadequate. It was not possible to torque them correctly without stripping threads. This is because over time the plating process may have made threads soft. I later installed grade 10 (black anodized finish) bolts which are stronger for this purpose. Make sure and use anti-seize compound on all threads. Another important TIP here: The factory supplies the carrier bushing mounts in a grey finish paint. I've carefully coated them in the Plasti-Dip rubberized spray to make a barrier around the metal. This can be a good way to treat metal that can't easily be treated by POR-15 because it needs bare metal to work the best.
Here is the subframe with both carrier bushings installed. Ready for the next parts!
This is the differential laying topside down with the retaining bolts inserted to the sub frame. In this photo, it doesn't show the fact I needed 4 washers instead of 2. You do need 4!
This view shows my 2002 Haus modified flanges with dual threads. This allows either 2002 or E21 half shafts.
Close up view showing the two different lengths of bolts used.
Alright! back view showing differential installed.
But wait... that's an E21 rear cover - that has to go!
"E S ??" This is a replacement 3:91 LSD, never installed on a car. The original E21 units just said "S".
Front view shown before E21 rear diff cover was removed.
Close up view of these 2002 Haus re-drilled LSD flanges. 2002's use the bigger of the two holes.
Top view of the differential mounted to the sub frame.
INSIDE: this is what a Limited Slip Differential looks like on the inside.
This one is ready for the Red Line Synthetic Diff lube. Remember, LSD's require special LSD lubricant for the clutch mechanism.
The ring and pinion gear as shown closeup.
Ok, this is the correct 2002 rear differential cover. The bolts that came with the E21 are too long. These two shown are just to keep it on for now till I add the fluid and new gasket.
This view shows where the two bolts will pass through the rear of the differential cover and stiffen up the mounting between the back of the differential and the car body itself.
This view shows the assembly laid out with new ST rear sway bars. They provide all the hardware you need, including these urethane bushings.
The tongue of this cover fits snugly against the sub frame and is held in place on both sides by two bolts.
OK, TII trailing arms, before they went into the bead blaster. These photos courtesy of Rob at  2002 Haus.
This is the bottom side, showing the boxed inner section.
Mass Production! A visual inspection shows some leftover slag from the factory.
In this photo, even a piece of the MIG welding rod was left behind.
Rob uses a die grinder to smooth out these spots and put on new welds prior to powder coating.
Aftwards! These look better than new.
Close up shows all the nasty welding bits are gone.
Nice Job!
These are on their way back to my shop for final assembly of the rear suspension.
More on this in the next few weeks.

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