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Old 08-23-2009, 06:08 PM   #1
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Join Date: Aug 2006
Location: Texas
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Official: DIY TMS Sub Frame Reinforcement

The Official Sub Frame Reinforcement DIY

I bring to you good people of the web the OFFICIAL E46 sub frame reinforcement DIY.

This DIY is not for the faint of heart, not only requiring the competence to turn wrenches, but also welding and cutting your chassis. Because of this I rate this DIY a 10/10. Only a professional welder should be used for this job.

During this DIY I choose to also replace all bushing that attach to the sub frame and will include that in the thread. These bushings include: 4 sub frame to chassis bushings and three differentials to sub frame bushings.

Please attempt at your own risk.

Step 1 Get your car in the air. I used a jack and four jack stands. I recommend getting it as high in the air as you can.

Step 2 Remove the rear wheels.

Step 3 Remove the exhaust. There are 4 - 13mm bolts in the rear, 10-13mm bolts on the middle cross members, 2-13mm bolts with rubber spacers that mount to the transmission, and 4-18mm bolts attaching the exhaust to the headers.

Step 4 Remove Driveshaft heat shield. 4-10mm bolts, 2 front/2 rear - will need extensions.

Step 5 Remove driveshaft.

a. Disconnect the driveshaft from guibo. There are 3-18mm nuts/bolts (44 ft. lbs.) that will require two wrenches to remove.

b. Disconnect driveshaft center carrier mount. 2-13mm (15 ft. lbs) nuts that attach to chassis.

c. Disconnect driveshaft from differential. You will need an E12 torx to remove these bolts. Get whichever ones you can get to. Then, release the e-brake from inside the car, rotate the driveshaft, and re-engage e-brake to get the other bolts. There are 4 total. (61 ft. lbs.)

d. Remove small aluminum shield. There are 2-10mm bolts holding it on.

e. Remove the aluminum guard at the end of the driveshaft. It has 4-13mm bolts (22 ft. lbs.) and 2-18mm bolts. (57 ft. lbs.)
f. Separating the driveshaft from the differential will be difficult. There is a lip (as pictured) securing the driveshaft to the differential.

g. A few taps of a rubber mallet and some elbow grease should do the trick. The driveshaft should now be removed.

Step 6 If you plan to replace the differential bushing, you will want to disconnect the axles from the differential now. It requires the same E12 torx bit the driveshaft to differential bolts required. There are six on each side. I used roughly a 1 ft worth of extension and stood outside the fender on each side. On the driver side, you will only be able to see and get to the bit on the bolt in the 2-3 o clock position. On the passenger side, you will only be able to see and get to the bit in the 9-10 o clock position. Mine took a lot of effort to break them loose. You will have to remove a bolt, then loosen the e-brake and rotate the axles, and then re-engage the e-brake to get to them all. It is easier if you have a friend to get in the car to handle the e-brake for you. (61 ft. lbs.)

This is why you don't take your car to a shop to have a new differential installed, or trust any shop your unfamiliar with for that matter:

Step 7 Unbolt shock from the hub on both sides. There is 1-18mm bolt (74 ft. lbs.) on each side. Support the hub with a jack before you loosen to prevent the hub being sprung down and damaging the brake lines. Repeat on opposite side.

Step 8 Now is a good time to disconnect the brake lines. Where the hard line meets the soft, there is an 11mm nut. Have something to catch the fluid, and unscrew this nut. Not much fluid should come out. You can now move the jack placed in step 7. Repeat on opposite side.

Step 9 Unbolt rear trailing arm from body. There are 3-18mm bolts (57 ft. lbs.) on each side. Make notes on their position.

Step 10 Coming from each brake assembly, there will be one or two wires leading to a black box mounted on each inner fender. Open these boxes and disconnect the wires.

Step 11 From inside the car, remove the parking brake boot. You will see 2-10mm nuts under the lever. Remove these nuts and washers.

Step 12 From underneath the car, pull on the two parking brake cables you see going into the body. Once pulled through, grip them by the control arm and pull them through the other body piece.

Step 13 Support the sub frame and everything else left. I used a motorcycle lift, it worked great but make do with whatever you have handy. Remove the 4-18mm bolts (57 ft. lbs.) holding the sub frame to the body. The front mounts may need a little crowbar encouragement to slip loose. Slowly lower the jack and roll the sub frame out from under the car.

Step 14 If you plan on replacing the sub frame and differential bushings while you have the sub frame out, now is the time to remove the differential. There are 2-18mm bolts (81 ft. lbs.) in the front, and 1-21mm bolt (128 ft. lbs.) in the rear. Unbolt these are remove the differential from the sub frame.

Step 15 Disconnect the rear control arms from the sub frame. There is 1-18mm (57 ft. lbs.) bolt on each arm.

Step 16 Disconnect rear trailing arms from sub frame. There is 1-18mm (81 ft. lbs.) bolt on each arm.

Step 17 Disconnect the sway bar from the sub frame. There are 2-13mm bolts holding it on.

Step 18 Your sub frame is free! Rejoice! I went and cleaned mine off with degreaser and a hose at this point.

Doing a lil sub frame dance:

Step 19 There are a few different ways to get the bushings out of the sub frame. I choose to burn them out. Sorry environmentalists, I don't believe in global warming.

Step 20 All of the bushings came out with ease with the exception of the rear differential bushing, which happens to have a thick metal casing around it. I took a reciprocating saw to it, careful not to saw all the way through. Then I proceeded to knock the crap out of it with a chisel and a mallet which did the trick.

Last edited by JSanders; 08-28-2009 at 03:30 PM.
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