Mike Miller’s article from European Car is an excellent resource for those interested in changing their diffs. It can be accessed here.

I bought my diff for $300 from a 533i owner. It was in pretty good condition, though I did replace the output shaft seals. These were easily driven into place with a large hex bit and a hammer. Additionally, I gave it a good cleaning, as diffs tend to get dirty by the time they have 150,000 miles on them.

Use the parking brake to set the rear wheels, as you will be disconnecting the engine/transmission from them while doing the swap. Remove the four nuts from the driveshaft/input flange coupling, and push the driveshaft forward. Then remove the six hex bolts from the output flange/inner CV joint coupling, being sure to support the halfshafts when they’re disconnected. The four bolts that hold the diff to the axle carrier are difficult to undo, but with enough penetrating oil, leverage, and cursing, they’ll come out. Make sure you’ve supported the diff by the time you remove the final axle carrier bolts! Finally, remove the bolt that goes through the rear bushing.

Installation is the reverse of removal. Be careful when you insert the axle carrier bolts not to crossthread them (as I did on one of them). The speed sensor that came with the new diff was different from the one that was on my old diff, so I had to swap them — just undo the two 10mm bolts that hold the sensor in place and pop it out. I also filled the new diff with Redline 75W-90 Gear Oil.

My car feels much more lively now than it did before. I’m not sure whether acceleration was improved, as shift points come up much quicker than they did before. However, my exit speeds from corners have improved significantly. Additionally, I can feel the limited-slip clutch pack working to put power down to both wheels while I’m exiting corners, and I’m sure snow performance is much improved as well. About the only downside is that The engine turns several hundred RPMs higher on the highway, though this also leads to increased passing performance.!

Zionsville Autosport has a great writup on replacing an E30 steering rack with an E36 rack. They used an E36 M3 rack with a 3.25 lock-to-lock turning ratio, but I used a (cheaper and more available) E36 rack with a 3.5 lock-to-lock ratio. Either will provide a nice upgrade from the stock E30 4.0 lock-to-lock ratio.

All in all, the conversion is fairly simple. The thing that took the greatest amount of time was bending the new high-pressure line to fit my car. Be sure to study the pictures on Zionsville’s site carefully before bending the high-pressure line. This will save you lots of aggrivation, and possibly from crimping the line (and they aren’t cheap, either; new ones are ~$200!).

Be sure to get the little metal clamps for an E36 steering rack boot, as the E36 rack has a larger diameter than the E30 rack where the boots mount on it, and the E30 clamps will not fit it. Also be sure to fill the power steering reservoir with quality ATF and bleed the system (with the front end raised, turn on the engine, and move the steering rack back and forth from lock to lock until bubbles stop appearing in the power steering reservoir).

This was a relatively good improvement in steering feel — it’s definitely a lot quicker now!

The new fluid, being synthetic, has made a huge difference in shift feel. Shifts feel much more natural, and much less notchy. It hasn’t gotten cold here yet, but one of the benefits of synthetic gear oil is reduced cold-shifting effort.

1. Replace with a factory exhaust, $300
2. Replace with an E30 325i exhaust, necessitating an new cat, ~$800
3. Replace with an Ansa exhaust, $150
4. Replace with a Supersprint exhaust, $500

I chose the Supersprint exhaust because of their reputation for quality and the power gains (a few horsepower) over stock. Ansa exhausts, while cheap, don’t tend to have a long service life. While the option of going to a 325i exhaust was tempting, the price was prohibitive.

The juncture of the connecting pipe and the catalytic converter with the Supersprint installed. Note new gasket and copper nuts and bolts, with anti-seize on them.

Replacing an exhaust system is not nearly as daunting as it sounds. We first removed the strap that supports the muffler (as the muffler and resonater had previously parted company). Then we removed the heat shield (several 10 mm nuts), and finally the entire bracket. We then removed the three bolts that held the resonator to the catalytic converter (see picture at left). This involved using both an 11 mm and 12 mm wrench, and a lot of grunting. A shot of penetrating oil probably helped us get the bolts undone.

New rubber donut and mounting strap. Don't forget to lube the donut with dish soap!

We were then ready to mount the new exhaust. Whenever you do exhaust work, use all-new nuts, gaskets, support straps, and rubber donuts. They’re cheap insurance. The Supersprint exhaust system is a two-piece affair. First bolt the connecting pipe to the catalytic converter, using a new gasket and new nuts. Anti-seize compound applied to the bolts will make the job a lot easier the next time around. Once the connecting pipe is mounted, turn your attention to the muffler. First install the

New rubber donut and the outside mounting point.

new rubber donut exhaust hangers on the car and support strap (see pictures). Apply dish soap liberally to the rubber donut to help ease it into place (trust me, it’s a bear without the soap!). Re-install the heat shield, and remember to put a little anti-seize on the bolts. Lift the muffler into position, and insert the end of the muffler into the connecting pipe, making sure the clamp is already in place. Install the lower part of the mounting strap on the muffler loosely. Now you can adjust the muffler so that it clears the body of the car and is level. Once you have finished this, tighten the clamp between the connecting pipe and the muffler, and finally the mounting strap.

The Supersprint has definitely been a worthwhile purchase. It is four pounds lighter than the stock exhaust, and has a nice throaty sound under acceleration. It is, however, not terribly loud. You can tell it’s there, but it is by no means obtrusive; in fact, I was a bit disappointed by the sound at first. I’m sure that I gained some power with the new exhaust, but gains are marginal and largely psychological.

Installation is fairly simple. First, remove the old speaker grilles; they should pop right out. Then unscrew the old speaker, and remove it from the housing. Pull off the wires and install them on the new speakers with a thin coating of dielectric grease for good measure. Screw in the new speakers, but don’t crank the screws down. Install the grille, and you’re done! The driver’s side is the trickiest part, as the hood release lever is in the way. You just have to hold it out of the way as best you can when removing and installing the speakers.

First, you need to remove the OBC. In order to do this, I took out the radio and the passenger’s side console side panel. The panel is secured by several nuts and trim screws, none of which are difficult to remove. Once you have access to the backside of the OBC, remove the four philips screws that hold it to the console. This takes some dexterity, patience, and foul language. The OBC then removes to the front of the console. The light circuit board is the white thing on the right side – remove it with a pair of needle-nosed pliers. Once it is out, remove the white plastic from the circuit board. Use solder wick to remove the old lamps, and solder in the new ones, being careful not to create a short. I didn’t find it necessary to re-install the little white lamp supports for the new bulbs.

At this point, re-install the white plastic “reflector”. Insert the board back into the OBC, and check that the lights work! It wouldn’t be terribly fun to put it all back together and find that it doesn’t work. If it does, sew the whole dash back up. I only installed two of the corner screws to hold in the OBC (the rest had disappeared behind the dash). It holds perfectly well, and now I can see my display!

Taillight gaskets are fairly easy to replace.  Simply turn the two black knobs on the taillight assembley to unlock it, and pull it from the outer housing.  Then undo the nuts holding the outer housing to the body.  Pull the housing out, and replace the gasket.

A bad trunk gasket is also easy to replace, but a little trickier to diagnose.  I finally tracked it down after a rainstorm when my car had been sitting on a hill.  Rainwater was flowing down the channels on either side of the trunk, and pooling in the little triangular-shaped depressions on either side of the trunk (below the rear window).  This water was then flowing over the trunk gasket into the trunk.  A few bucks and a few minutes later, my trunk was water-tight again!

I changed my brake pads to Cool Willies, available through Turner Motorsport. I did this because Metal Masters disintegrate under the high temperatures encountered on the track. The pad swap is fairly easy: put the car up on jackstands and remove the wheels. In the front, there’s a bolt that secures the caliper to the carrier. Remove the lower bolt and swing the caliper up, freeing the brake pads. Installation is the reverse of removal, but you may have to push in the piston slightly for the new pads. Use a piece of wood and a pair of water pump pliers to accomplish this task. Be sure to use a new bolt in the front calipers. They are single-use only! The rear pads are similar, but here you’ll have to remove two 9mm hex guide pins to remove the entire caliper.

Update: I used the Cool Willies again for my second driver’s school at Second Creek in Denver. Second Creek is notoriously hard on brakes, and I noticed that my brakes went away to a large degree during the day. Upon changing back to street pads, I noticed that the Cool Willies had pitted and cracked to a significant degree. Asking around, I discovered that the carbon-kevlar Cool Willies aren’t as heat resistant as carbon-metallic pads. Next year, I’ll likely run PF-90s.

I also flushed my brake fluid — a procedure that should be done at least yearly, as brake fluid loves to absorb water (which then boils, leaving you with very reduced brake performance!). I used the brake bleeder cap available from Steve D’Gerolamo. This work of CNC’d aluminum art uses air pressure to force old brake fluid out of the system. If you don’t have a source of compressed air, don’t fret. Simply go to your local home and garden store and pick up a fertilizer/week killer sprayer. Cut off the sprayer from the hose and attach the hose to the cap with a hose clamp. (Be sure to use a hose clamp, or you could end up like me, cleaning caustic brake fluid off my paint after the hose parted company with the fitting!) Attach a some sort of reservoir to the bleeder screw to catch the old fluid as it’s expelled, and begin bleeding from the side farthest from the master cylinder (the rear passenger-side caliper). When new fluid flows from the caliper and is free of bubbles, you’re done!

Removing and replacing the springs and shocks is a time-consuming and potentially dangerous job! You’ll need a few special tools: a spring compressor (this is not a time to be cheap — springs make wonderful lethal projectiles!), a breaker bar, a tie rod pickle fork (I used a 21/32″ fork for the job), and a large pair of water pump pliers.

I tackled the rear first. Put the car up on jackstands, and make sure that it’s not going anywhere before doing anything (i.e., give it a good shove from every direction and make sure it doesn’t move). Remove the sway bar link from the trailing arm and pivot it out of the way. This gives you some more room to work. Put the spring compressors on the spring. I found that I had to put one with the threads facing up, one with the threads facing down due to clearance issues. Get the spring compressors as far on either side of the spring as possible. Compress the spring evenly until when you try to screw the spring compressors any farther the spring rotates in its perch. You can now remove the shock to drop the trailing arm a bit further. The upper shock mounts are in the trunk behind the paneling; the paneling is a PITA to remove, but it does come out. Now press down on the trailing arm (I stepped on the caliper) to the point where you can slide the spring out from its perches. Be very careful with the compressed spring, as it is a loaded weapon! You might as well clean the perches up while you’re in there.

Transfer the rubber pads to the new spring. I needed to compress the new springs slightly in order to get them to go back in. Once the springs are seated, you can put the new shocks on. Use new strut mounts, as they are cheap and good insurance against an old one going bad on you. Just bolt everything back up, being sure to use a new gasket between the shock mount and body. The bolt to to trailing arm needs to be torqued down pretty well, and it might not be a bad idea to use lock-tite on it. Remember to re-connect the sway bar links.

The front suspension uses struts, and is significantly more involved. Start by removing the brake calipers. The bolts that secure them to the strut are torqued to ~90 lb-ft, so you’ll need a breaker bar to get them off. Turn the steering wheel to lock in order to gain more clearance to work. Slide the calipers off the disc and support them on a block of wood under the car. Do not let them hang by the brake line! Next remove the bolts connecting the outer control arm ball joint and tie rod to the strut. These are not too hard to get off; again, turn the wheel to lock to get more working room. Use the pickle fork seperator to loosen the ball joints from the strut. Be forewarned that you can easily destroy the ball joint dust boots. This isn’t a big deal for the tie rods, as you can replace them easily, but to replace the control arm dust boots, you need to remove the entire control arm! You may need to remove the sway bar link so that you can pivot the control arm downwards to clear the strut. At this point, you can remove the three nuts from the shock tower (while supporting the strut from below) and remove the strut from the car.

Use the spring compressor to compress the springs as far as you can. Make sure that there is no tension on the upper strut bearings when you release them, or they will become deadly projectiles! Use a deep well socket on the big mounting bolt here, and thread a smaller socket through the hole to fit on the strut itself. You can use a pair of vice grips on the big socket and a ratchet on the smaller one to remove the bolt. Remove the bearing, spring perch, pad, and spring. Pay attention to the order in which parts come off to make installation much easier! To remove the strut insert’s locking collar, we placed the collar in a vice, put two big bolts through the ball joint mounting points, and used a pry bar to turn the strut. Alternately, you can use the water pump pliers to remove the locking collar. Pour the old oil out of the strut — you do not need to add oil to the strut if you are using gas-pressure shocks (such as Bilsteins).

Put the new strut insert in the strut. The little nylon ring slides over the strut tube, below the lock ring. Torque the lock ring down pretty good (Bilstein says 90 lb-ft). Before installing the spring, place the blue protective boot over the strut insert. It is held in place by the nylon ring at the bottom, and the spring perch at the top. You’ll need to compress the new spring a bit to get the perch and bearing back on. This is not a complicated procedure, but it does take some time to get the spring to line up correctly with the perch. Use the two-socket method to tighten the upper mounting bolt.

Because we tore one of the dust boots on the tie rod and mashed the bolt pretty good, I decided to replace the tie rods. Cut the clamp on the tie rod protective boot, and slide the boot back to gain access to the inner ball joint. You don’t need to completely remove the boot to do this. The tie rod is secured by a lock washer against the steering rack. I used a screwdriver and a hammer to bend the lock washer tabs back to nearly planar. At this point, I used a pair of vice grips on the inner ball joint to unscrew it from the steering rack. Before installing the new tie rod, try to match its length to the old one. The new rod screws into the steering rack; be sure to place the lock washer in between first! The tab on the lock washer mates with a notch on the steering rack. When you have the tie rods screwed on tightly, bend the lock washer over the inner ball joint. There is almost no clearance on the top, so do the best you can, but the bottom is easily accessable with a hammer. Re-attach the protective boot to the new tie rod.

To install the strut, first attach it to the shock tower. Place the ball joints into their respective holes. Place a jack underneath the ball joints, and press them upwards against the strut. This puts tension on them and allows you to thread on the self-locking nut without the joint spinning. Be sure to use new self-locking nuts on the ball joints. Re-attach the calipers, being sure to torque them down really well. After any sort of suspension work, you should have an alignment performed.

I absolutely love my new setup. We measured the drop, and compared to the specs in the Bentley manual, the new springs lowered the car by 1″. It looks really good, and performs even better. In fact, the new suspension feels more compliant over small pavement imperfections than the stock suspension. However, my car now corners absolutely flat, not to mention more neutral. I can control the cornering attitude much more with the throttle now, and there’s not that annoying wait before the suspension takes a “set” in a corner. It is exactly what I wanted: noticibly firmer than stock, but not kidney-jarring.

Many thanks to Neil Deshpande and Jack Money for helping me with this project!