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Official: DIY TMS Sub Frame Reinforcement

156K views 109 replies 55 participants last post by  evilpinkeye 
#1 · (Edited)
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 ½ 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.
 
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#32 ·
i need to do this very soon. i have a bad subframe bushings and im hoping i dont have any cracks.

my only problem is i am not the best of welders and wouldnt trust my welding on that, i only trust it on exhuast. lol. i wish i could take out the subframe and take it to a shop to weld it but its kinda hard getting a car with no rear wheels towed without damage.
 
#34 · (Edited)
The guy that did the welding on my car came from UT Tyler's welding program, the top of his class. If you have a local college with a welding program, you should go talk to one of the teachers to find out who his best welding student is and offer him a few bucks to do the job. People are always looking for ways to make money now a days.

Yeah you saved me about £600 so it was worth it! I finished up putting it together, took me 6 weeks because real life kept getting in the way! I took it out for it's maiden voyage and realised my brake pedal was going all the way to floor so i must not have bled it properly. I took it back home, and broke one of the bleed nipples off :ben: I popped a screw extracter in the hole and tried to get it out, but that snapped off too :facepalm: So now i'm waiting for an ebay caliper so i can finally get my beloved car back... I took some pictures, i'll put them up once i get them off my phone
I hope you get it going soon!
 
#41 ·
when we did mine, we just hung the calipers...

it took me and 2 of my buddies 1.5 days to do the same thing.. the buddy who's house we were doing the work at is a welder, and fabricator by trade so we were good to go there... it took him about 1-2 hr's of welding to get everything done. and he has done 4 other cars besides mine. so if you are talking with a welder, I would say between 2-3 hrs depending on their experience...

I would disagree with the gas tank and leaving it in place... There is no way that i would do this with the gas tank in the car.. even if you are careful... that is the LAST thing you want going wrong. It doesn't take that long to take the Gas tank down.. also try to have 1/8 or less gas in the tank.....


if you are doing this, its really the perfect time to do anything on the rear suspension. ball joints/bushings what ever.

like others have said, this really isn't that "Hard" but the welding can be quite intimidating. I have seen some guys MIG weld this in, but i would reccomend not MIGing it in, but make sure that the welder is TIGing.. much stronger weld.
 
#43 ·
+1

Although TIG welding is undoubtedly a stronger weld, I feel that a MIG weld is strong enough for the reinforcement. Had a TIG welder been available to me I definitely would have used it, but I feel a MIG welder can handle the job if one is not available. It's been over a year since mine was repaired and it is holding up fine. I am an aggressive driver, too.


Is this reinforcement any different than the class action lawsuit subframe inspection and repair? I just took mine to the stealership an they're ordering parts.
I believe if BMW performs the repair they actually cut the section of the frame out that is prone to cracking and weld in a new "updated" chassis piece. Some are able to have the TMS reinforcements welded in by the shop performing the repair during the process, others are not.
 
#42 ·
Is this reinforcement any different than the class action lawsuit subframe inspection and repair? I just took mine to the stealership an they're ordering parts.
 
#44 ·
I'll try to get at least a part number for what the dealer ordered and try like hell to get a pic of what they're installing. I'll post pics i I get them.
 
#49 ·
Started mine yesterday. Subframe is out. Hardest part is going to be cleaning all the junk out of the trunk of my car. I've been putting it off until absolutely necessary.

Edit: forgot to say...BIG BIG thanks to the op. The diy simplified the process for me greatly and kept me from having to look for my bentley manual.
:thumbsup:


So it's ok to just to weld the 4" crack? How big of a crack would you have to have on your chassis to require you to replace that whole part like BMW did in the suit?
Short answer: Find an experienced welder/fabricator that you trust, have them look at your car and ask them.

In my circumstance it was fine, I've done a lot of metal work back in high school and my buddy that did the work for me welds for a living, so we knew that it would be fine to just weld my crack before reinforcing.
 
#47 · (Edited)
Started mine yesterday. Subframe is out. Hardest part is going to be cleaning all the junk out of the trunk of my car. I've been putting it off until absolutely necessary.

Edit: forgot to say...BIG BIG thanks to the op. The diy simplified the process for me greatly and kept me from having to look for my bentley manual.
 
#48 · (Edited)
So it's ok to just to weld the 4" crack? How big of a crack would you have to have on your chassis to require you to replace that whole part like BMW did in the suit?
 
#59 ·
Three words for you, jsanders: Damn you rock! So how much did all this cost you monetarily? I was thinking of asking a BMW tech to do a little moonlighting because I can't afford the dealership. Don't want to cheat myself or them for their labor. This post makes me so optimistic. Thought I'd have to trash my baby due to all the repair work needed. Thanks again (that's more than 3 words huh? :) )
 
#60 · (Edited)
:thumbsup: Glad you all are getting some use out of this!

IIRC, the subframe reinforcement kit was ~ $150, the primer, paint, sealant foam and underbody coating was ~ $40, $10-20 for the brake fluid... So I guess around $200 total. Could be forgetting somethings, but I'm pretty sure I already had everything else needed.
 
#61 ·
DIY is helping a good amount thanks to the op/

And whoever said you need a TIG welder to do this... is wrong. MIG is over the top strong enough for this. I've welded thicker than 0.25" plate with MIG. All depends on your welding setup and the welding machine.

Although it seems I have a slightly steeper mountain to climb.





To anyone who was wondering why you need to cut into the trunk as part of the reinforcement kit... here's why.

 
#63 · (Edited)
Welcome to ontario, canada.... the streets are ligitimately white for a few weeks after the snow clears in larger cities from salt residue.

Subframe cleaned up nicely though, and the metal under the car is still solid everywhere. just tore out where the cracks started i guess.

Side note: spoke to a local BMW dealer and the service manager was helpful but stated due to the age of the vehicle, BMW now typically only covers about 20 % of the repair costs (in other words still around 3000 out of my pocket... at least)
 
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