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Old 12-18-2006, 09:28 PM   #1
mohaughn
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Default subframe removal/overhaul

So I got an estimate to have all of the bushings replaced on my car and the labor to uninstall the rear subframe, change the bushings, and put everything back is pretty high. So right now I plan on completely removing the trailing arms and the rear subframe and just have a shop press out the old bushings.

So after looking through the bentley and haynes manuals I have a pretty good idea of what is involved.

The only things involved here that I've not done before is removing the drive shaft, half shafts and the differential.

So two questions, anybody have any tips on doing this job? I'm guessing it is a two person job when it comes to dropping the differential and actually dropping the subframe. Or can it be managed with one person a good jack and maybe some extra jack stands for extra support?

Also, what items are throw away items? I'm not sure what nuts involved are nylocks,which bolts should just be replaced, and where crush washers are used it they are. The haynes manual says some of the bolts related to the drive shaft and half shaft should be replace, but it doesn't say specifically which ones. I'd like to go to the dealer and get new nuts/washers, and bolts that I need before taking everything apart.
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Old 12-18-2006, 09:57 PM   #2
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do you have air tools? heat ?
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Old 12-18-2006, 10:15 PM   #3
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how expensive? i had mine completely re-bushed for £300.
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Old 12-18-2006, 11:56 PM   #4
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1500$ to do everything, front coilovers, x-brace, front subframe reinforcement, rear trailing arm bushings, rear coilovers, motor mounts, diff bushing, control arms, subframe bushings... Book rate has it at 24 hours of labor, but I was quoted the actual amount of work when you start combining items.. But I've already completed the control arms and eyeball arms, and once I get the rest of the parts the front suspension will be done. Honestly it isn't that I think it is an outrageous amount of money to do it, I just have the time coming up in the next couple of weeks to drop the subframe myself and upgrade the rear.

What does a torch have to do with removing the subframe? Or air tools for that matter. I'm going to have the bushings pressed out on a hydraulic press, so I don't have to use the DIY methods of using an air chisel and a torch to get the subframe bushing out. The methods that I have read that use an air chisel and a torch are only when you don't want to completely remove the subframe. But that is why I'm asking. Sometimes the manuals and DIY articles make things seem easier than they really are.

Air tools would be nice for working on some of these high torque bolts though.. But it is a good workout trying to break loose these pesky bolts..
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Old 12-19-2006, 12:00 AM   #5
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I've dropped the entire subframe. I did it by myself with just a floor jack and I did not remove the differential of half-shafts. The whole rear came down as one unit. No air tools either. I think having a nice big 1/2" drive ratchet and some 1/2" drive metric sockets covers almost the whole car.

By memory....

• Break loose the big main subframe nuts. There's one on each side and they sit vertically.
• Break loose the rear wheel lug bolts.
• SAFELY and securely raise the rear half of the car. I used two heavy duty jack stands, plus two more lighter duty ones to back them up. I also put the rear wheels under the rear half of the body for another backup.
• Remove the rear wheels.
• Remove the spare tire.
• Remove the exhaust. Unbolt it at the spring connection, not at the manifold. Mine were in bad shape and they snapped. Buy new ones to have on hand. It's kind of awkward to lower. A helper would be nice, but I used a jack stand to help a bit.
• Remove the parking brake cable lock nuts, up at the lever. (4 total)
• Unplug electrical connections (brake pad, wheel speed sensor)
• Disconnect brake lines at the forward most flexible flexible hoses. It'll drip like crazy, so be ready to catch a lot of fluid. It seems to drip forever too. (You might actually want to do this step as late as you can, then you won't have dripping fluid getting in your way)
• Unbolt the sway bar links. Or, I might have unbolted the sway bushing brackets at the body and let the bar stay attached to the suspension.
• Remove all the heat shielding below the driveshaft. There's a small tunnel crossmember in there also. Make sure you get rid of that because it'll help you lower and flex the rear half of the driveshaft.
• Unbolt the four nuts/bolt at the differential to driveshaft connection.
• Loosen, but don't remove, the differential "ear" bolt/nut.
• Place the floor jack under the center of the differential. This will be close to the balance point of the entire subframe. Jack it up so it takes some weight.
• Remove the lower rear shock bolts.
• Remove the differential "ear" bolt.
• Remove the two main subframe nuts.
• Remove the subframe reinforcement plates. These are sandwiched between the subframe bushing and the main subframe nut. There are two bolts on each side that bolt the plate to the body.

From what I can remember, that's all that's connected.

• SLOWLY start to lower the subframe. Make sure it's feeling balanced! The whole unit is heavy, so be careful with it.
• The driveshaft will need to flex downward (at it's u-joint) and you drop the subframe, so make sure it's free to flex down.
• Once the subframe bushings have cleared the big main studs, you can start rolling the subframe backwards. That will allow the driveshaft to come out of the subframe "hole" that it's in.

It should be clear of the car now. It seems like huge job, but it's quite straight-forward.

As for the bushings, you can then unbolt the rear semi-trailing arms from the subframe, and work on those bushings. Check out my little write-up on that. It shows how I pulled and pressed my semi-trailing arm bushings. http://www.318ti.org/forum/showthread.php?t=9861 You'll be able to press in/out the semi-trailing with the half-shafts still bolted to the differential. If you want more working room, you could unbolt the six (?) half-shaft torx bolts and pull the trailing arms from the subframe.

My number one suggestion for pulling the trailing arm bushings is USE HEAT!!!! Heat soak the bushing with a propane torch before you start pressing them out. I tried this earlier without a good pressing tool OR heat and it was horrible. They are small bushings, they are very tough! The method I used in my link worked wonderfully

As for the subframe bushings, that was a different story. I welded up a pretty good pulling tool, but I never used heat. The bushings were in there so strongly that it broke my steel tool I'm quite certain if I used a propane torch they would have come out without an issue. I ended up drilling them out, and hacking up my subframe. I replaced them with urethane bushings, so installation was simple. Reinstallation of stock bushings would have required a good press and some bushing lube. Please don't underestimate how tough these suckers are. They are amazingly stout.

If you look in my link, you'll see I used a plain synthetic grease to reinstall the trailing arm bushings. BMW has something called "Circolight mounting agent", but I've never been able to find it. One thing I used lately on bushings was "Goo-Gone" sticker/gum/wax remover. It make the rubber bushing really slippery, but if you let it sit out, it'll evaporate, just like the Circolight. I wouldn't attempt to install these bushings dry.



My suggestions for stuff to replace....

• Trailing arm bolts and nuts (Four bolts, Four self locking nuts) If you think about it, these bolts are rather important, so I wanted new ones.
• Differential "ear" nut. It's self-locking.
• Rear driveshaft self-locking nuts. Four total.
• Main subframe nuts. Two total.
• Exhaust bolts & nuts. Two bolts and two nuts (?) They are the long skinny bolts that go inside of the springs.
• I replaced my rear brake hoses while I was at it. Four total.
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Old 12-19-2006, 01:17 AM   #6
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Thanks. I guess I need to spend some time on realoem rounding up part numbers for the different bolts and locknuts...

I got the urethane bushings from Ireland Engineering and he included a bushing lube with the trailing arm bushings, so I should be good there.

If I'm going to completely remove the subframe from the car, including the trailing arms, I'll half to remove atleast the half shafts right? I plan on taking the trailing arms to a machine shop and having some reinforcements welded into them. I think the Bentley manual tells you to remove the driveshaft and both half-shafts. Although, I was also planning on having the bushing pressed out of the differential, so that kind of requires removing the drive shaft as well.

I just don't want to end up spending hours drilling, sawing, heating, and banging away at old bushings.. Seems to me to be a much better idea to take it to a heavy duty shop press and have it done in a matter of minutes.
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Old 12-19-2006, 01:32 AM   #7
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Try to find a shop that has the rear subframe bushing tool. We have one and regularly do the rear subframe bushings for, I think, 4 hours a pair (dealer charges 8.) We rarely do trailing arm bushings (I have never, actually.)

You can drop the whole subframe assembly pretty easily.
Exhaust
Upper shock mounts
Brake lines
Parking brake cables (either end)
Rear diff mount
Driveshaft
left and right subframe nuts

Probably not in that order, but you get the idea. After that you can strip the subframe quickly of diff, trailing arms, etc.
-Paul
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Old 12-19-2006, 05:59 AM   #8
mohaughn
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http://www.realoem.com/bmw/showparts...99&hg=33&fg=30

Does anybody know the part # for #10? It would be the nut to match:

HEX BOLT M12X1,5X90 4 33321136406



edit- I found it.

SELF-LOCKING HEX NUT M12X1,5-10-PHR 07129900047

Had to look it up under an e30.
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Old 12-20-2006, 05:12 PM   #9
mohaughn
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Man.. BMW dealers can really rip people off..

My wife took her car in to get it serviced and while she was there I gave her a list of parts that I needed from the dealer.

10 lock nuts for the front/rear struts.
Lock nuts and bolts for the trailing arms
New lock nuts for the differential and the remainder of the subframe.
New rear strut gaskets.
5mm rear spring pads, and new upper spring pads.
2 exhaust hangers
and 2 exhaust spring "connectors."

They wanted over 140$ for the parts so when I asked what the price was before the BMWCCA discount she realized that they didn't give her the discount... With the discount it was 65$. The dealer said that they charge full retail list price to walk up customers to help pay for the new sales building and parking garage that they just built. The wanted almost 2$ for 1 lock nut... And almost 20$ for 1 exhaust hanger.
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