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Old 11-14-2007, 01:11 AM   #1
thefoxkazan
Registered User
 
Join Date: May 2006
Location: USA
Posts: 17
My Ride: 00' 323i 5spd Stick
Cool DIY : Replacing rear differential bushings (mounts) aka notorious rear end clunk

I MUST WARN EVERYONE!!! THIS DIY IS NOT FOR THE FAINT HEARTED!!!

I have always fixed cars myself, and I have had some hardcore projects like major engine repairs. But this simple looking bushing replacement was the toughest one so far. My car was up on the jacks and with rear end apart for more than 2 weeks(!!!), and I have spent countless hours in stores, supply houses and BMW dealership looking for parts and trying to figure out a solution. See some destruction pictures at the end of the DIY.

Difficulty Level : 9.5 out of 10. [royal pain in the arse]
Having the right tools: 5 out of 10.

Pictures have notes scattered across them, so please check every picture in this DIY if you can't find the part I am talking about.

Parts needed:
1. RUBBER MOUNTING FRONT (2) 33176770788 $28 each (approx.), #7 on diagram
2. RUBBER MOUNTING REAR (1) 33176751808 $54 (approx.), #9 on diagram



Tools needed:
1. 10mm socket.
2. 13mm socket.
3. 18mm socket.
4. 17mm socket.
5. 21mm socket.
6. Torque wrench capable of going higher than 120 ft/lbs.
7. E12 External Torx Socket (available as part of Torx Kit at Sears, Auto Parts stores, etc.)
8. Front bushing puller [SPECIAL TOOL].
9. Rear bushing puller [SPECIAL TOOL].
10. Misc stuff - extensions, screwdriver, hammer, etc.

Tools #8 and #9 are available as a kit, you can order them on the internet for $379 + shipping... yeah right. You can also make them yourself from parts you can get at hardware stores and plumbing supply houses ($60 for both tools maximum, depending on your location).

1. Drive the front of the car on ramps. Jack up the rear.
I usually put my huge hydraulic 3.5 ton jack under the carrier (sub-frame), it is right below the differential, a big steel brace, and jack it up until I can get my jack stands under standard jacking points on both sides on the car (they are under rear passenger doors on E46 sedans and have square rubber mounts on them).



2. Remove rear sway bar
(on the picture, out of the car)



I did not remove rear wheels. If you want to make your life easier, before raising the car up, release the lug bolts and remove wheels when the rear end is up. I didn't do that myself, it is not necessary, but you will have to reach in some tight spots with 17mm socket to prevent bolts from spinning.

This part doesn't have many pictures - I'm sorry I forgot to take them.

a. Remove bolts holding endlinks, 13mm nut and bolt (17mm bolt head). 25 ft/lbs tightening torque. 4 bolts, 2 on each side of the car.

b. Remove bolts holding metal tabs (they go into what I called "sway bar mounts" on the picture near part 9). 13mm nut and bolt (13mm bolt head), 16 ft/lbs tightening torque. 2 bolts, 1 on each side of the car.

c. Remove the sway bar (should be fairly easy, but remember how it goes in, so you don't have to mess around with it later).

3. Remove exhaust hangers, drop exhaust.

Hangers are very close to the end of the car. Both are rubber, one on each side, easily seen from below. (4) 13mm nuts, two on each side.

Drop the exhaust and let dangle. It is pretty strong - nothing will happen to it.

4. Remove rear suspension reinforcement brace.



a. Remove little flat aluminum heat shield (it is on the left-hand side of the car, where the exhaust is). Two 10mm bolts, don't lose them!

b. Remove (4) inner 13mm bolts, two on each side of the drive shaft (see picture). Tightening torque 22 ft/lbs.

c. Remove (2) big 18mm nuts, one on each side of the brace. Tightening torque 57 ft/lbs.

d. Remove the brace. You should see subframe mounts behind it, where you took 18mm nuts off.

5. Disconnect the drive shaft.



I recommend having a friend or a family member to help you with this. I was alone so I had to run back and forth to put the emergency brake on and off every time I had to reach for the next bolt. If someone will be pressing on brakes for you - it will be a lot easier.

a. Use a center punch or a white-out to mark locations of drive shaft relative to the differential input flange. Don't forget to do this! It could affect balancing of your drive shaft.

b. Use E12 external torx socket and an extension to remove (4) torx bolts holding differential input flange and drive shaft together. You're gonna have to apply a lot of force to get these off. BE VERY CAREFUL!!! TORX HEADS ARE DAMAGED EASILY IF YOUR SOCKET SLIPS OFF OR SPINS ON AN ANGLE. Once you have ripped the torx ribbing on the bolt head, you're pretty much stuck with it.

c. Spin the drive shaft as necessary and lock it back with an emergency brake to access each of the (4) bolts.

(4) E12 torx bolts, 61 ft/lbs tightening torque.

6. Disconnect left and right axles.

a. Suspend both axles with plastic wire-ties or a piece of wire/string. Wire-ties work very well because you can readjust them later on. Mark positions of output flanges relative to the axles so you can put everything back exactly the way it was.

b. Spin the wheels as necessary to access each of the (6) E12 torx bolts on each of the axles. Lock wheels with emergency brake to apply torque and release bolts. Use extensions as necessary and a big breaker bar. But AGAIN, BE CAREFUL, TORX HEADS ARE EASILY DESTROYED IF YOUR SOCKET SLIPS OFF.

c. Remove (12) E12 torx bolts connecting left and right axles with their respective output flanges on the differential. Tightening torque 59 ft/lbs.





7. Remove the differential.

a. Support differential with a jack. It is pretty heavy, believe me. Don't jack it up, just have the jack under it and ready to receive the diff when it drops.

b. Remove two 18mm bolts in the front(no nuts, they screw straight into the differential body). These are the ones going through two small front bushings. Tightening torque 70 ft/lbs.

c. Remove the rear 21mm bolt (21mm nut). This one goes through that single rear differential bushing, notorious for its "rear clunk sound". Tightening torque 128 ft/lbs.

d. Work the diff out towards the rear end of the car. Help of another person is preferred, although I did everything myself (it fell right out... on my chest... )



8. Remove the front bushings.

a. Note the position of the old bushings. They have arrows and letters telling you which way they are installed. Also note how far do they stick out of their wells (mine were sticking out about 1/16th of an inch towards the front of the car).

a. Assemble the special tool for removal. Use a special tool (either an ordered one or self-made) to remove each of the bushings.

b. Reassemble tool for installation. Position new bushings in their holes with arrows "TOP" pointing up and with the proper ends pointing toward the front. Press the new bushings in one at a time. Make sure they are going in straight and exactly parallel. It is a very tight fit, there is no room for tolerance(!!!) If they start to warp inside there, you are basically doomed (off to a dealership to buy a new bushing). SLOWLY WORK THEM IN. LOOK FOR ANY MINOR DEVIATIONS IN DIRECTION. Correct them with hammer if necessary, tap on either side of the bushing to straighten it out.

c. Once pushed in, check again for proper alignment. Get an energy drink... or two.

9. Remove the rear bushing.







This is where the fun starts. I couldn't get this one out. Heating everything up with the torch didn't help. All the special tools have failed. It took me 2 weeks to get this one out. Steel floor flanges almost 1/4" thick have cracked and failed. Extra strong 1/2" bolts ($9 a piece!!!) have snapped in half and got bent like soda straws. Steel casing on a bushing has a large surface area and metals just fuse together with time, so I just couldn't get it out using "normal methods".

In the end I was so mad, I couldn't take it anymore. So it was destined for me to switch to "ghetto mode" (whoever coined the term, it sounds just right) It was dark outside, I've had a long day at work and by that time spent 4 hours under the car. I took the drill and drilled the heck out of rubber shell inside the bushing. Then I knocked the core out with the hammer. After that I took a hacksaw blade and slowly sawed a groove inside the outer jacket. It took me more than one hour - slow and sure, careful not to damage the bushing "well" (or a hole to call it simpler). Hardest task ever! You are under the car, all crooked and bent in various shapes, banging your head into the car, trying to get a nice groove with little blade up inside the bushing.
Then I got my flat chisel, and simply chiseled the world out of that bushing shell with the biggest hammer I had in my garage. I was laughing like an evil genius, enjoying my insanity.


And now here's the normal way:

a. Assemble the tool for removal. NOTE THE BUSHING ALIGNMENT AND POSITION (you will need to install a new one the same way).

b. Heat up the bushing receiver arm with torch. You can burn the paint off, make sure you get everything heated good. That should break that metal bond and help release the bushing.

c. Keeping everything parallel and straight, push the bushing out into the receiver cup. Grease the threads! This is a must!!!

d. Clean off inside of the hole with a clean rag or a scrubber.

e. Assemble tool for installation. Position the bushing properly. Slowly work it into the hole with a tool, checking for parallel alignment and a straight direction. CAREFUL!!! DO NOT WARP IT!!! Tap it with a hammer if necessary to straighten out.

Forces required to do this are very strong. Look at the pictures of my aftermath and imagine what it takes to tear 1/2" high grade bolt apart. Or to fracture 1/4" thick steel plate. That's how much force is applied. So you have to be extremely careful - it will get damaged fast and easy if pressed in wrong!!! Worst of all it could get stuck in there pretty bad!!!

10. Follow all the steps backwards to reassemble everything.
Don't lose any screws and follow torque specifications. Everything should be a lot easier now.

The aftermath (what could happen to you):



* SPECIAL TOOLS

You can get all the required parts at a local hardware store and/or most of the plumbing supply houses, except for the parts I have noted as important/special. I had to get them specifically made, machined and cut precisely to my specs.

I will be selling both tools to the next enthusiast who wants to perform this DIY. I don't need any profit - I will sell them for just enough to cover the cost of all the parts I bought for them. PM me or I can make a separate post for them.

I. Special Tool for the two front bushings.





II. Special Tool for rear bushing.



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