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Old 04-12-2013, 06:56 PM
tjh54 tjh54 is offline
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Are there any DIY on rear sub frame bushing removal?

It looks like I need to replace my rear sub frame bushings my 2001 Z3 3.0i roasters. I read that there is a way to remove the bushings without having to remove the rear end. Has any made a DIY on this? This car is only used on the street.
Thanks for the help.
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  #2  
Old 04-12-2013, 07:26 PM
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This...
http://forums.bimmerforums.com/forum...for-uber-cheap!
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Old 04-12-2013, 11:37 PM
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^ DIY with proper tools and you're good to go!
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Old 04-13-2013, 05:35 AM
KBH22102 KBH22102 is offline
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+1 on that DIY writeup. I made my own shadetree tool as well and it worked fine. I did not do the heating step as the plastic fuel tank is only a short distance away on the passenger side. It's fine if you are careful, but I emphasize BE CAREFUL. The heating process may also compromise some of the rustproofing treatment and make the carrier a bit more prone to corrosion if left untreated.
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Old 04-13-2013, 05:44 AM
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Quote:
Originally Posted by tjh54 View Post
It looks like I need to replace my rear sub frame bushings my 2001 Z3 3.0i ...
How many miles on the car, and how can you tell when the bushings need replacement?
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Old 04-13-2013, 06:26 AM
Blacklane Blacklane is offline
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Quote:
Originally Posted by vintage42 View Post
How many miles on the car, and how can you tell when the bushings need replacement?
The consensus is that if they are original, they need to be replaced. That's because BMW installed fairly soft rubber there, which causes the subframe that holds the differential to move too much. That causes too much force on the center differential mount, which leads to failure of the spot welds in the trunk floor costing thousands of dollars to repair.

New, harder polyurethane mounts help stiffen the attachment at the ends of the subframe.

That being said, you have a 1.9 liter engine. The diff mount failure is almost unheard of on cars with the 1.9 and/or ones with automatic transmissions. The only real reason to replace the rear subframe bushings on those cars is to improve the feel of the rear end and eliminate a little wobble in hard cornering.
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Old 04-13-2013, 06:31 AM
Wertles Wertles is offline
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Here is another step by step DIY.

http://dl.dropboxusercontent.com/u/6...IEBushings.pdf
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Old 04-13-2013, 07:13 AM
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Quote:
Originally Posted by Blacklane View Post
The consensus is that if they are original, they need to be replaced. That's because BMW installed fairly soft rubber there, which causes the subframe that holds the differential to move too much. That causes too much force on the center differential mount, which leads to failure of the spot welds in the trunk floor costing thousands of dollars to repair. New, harder polyurethane mounts help stiffen the attachment at the ends of the subframe.
That being said, you have a 1.9 liter engine. The diff mount failure is almost unheard of on cars with the 1.9 and/or ones with automatic transmissions. The only real reason to replace the rear subframe bushings on those cars is to improve the feel of the rear end and eliminate a little wobble in hard cornering.
Thanks for the explanation. I understand that power transmitted through the differential mount stresses the spot welds holding channel-beam under the trunk floor.

Are road forces like cornering and braking also transmitted to the welds of this beam?

Does "rear subframe" refer only to the channel beam welded under the floor, or also to the suspension part that carries the differential shown in this photo? The Randy Franks rear subframe kit seems to only replace the channel beam.
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Last edited by vintage42; 04-13-2013 at 07:15 AM.
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Old 04-13-2013, 07:57 AM
Blacklane Blacklane is offline
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The terminology gets a little vague since there isn't a good name for the part of the car that breaks. Technically, the Rear Subframe is the piece that mounts on each side of the car and holds the differential and the two Rear Trailing Arms. (It's the piece shown in you picture). The part that breaks is the unibody cross member that supports the differential mount or mounts, depending on which differential cover is installed.

You can find many threads here on the Randy Forbes reinforcing kit which strengthens the cross member and diff mount attachment. I've never seen him do a single-ear mount; I suspect he recommends replacing the diff cover with a dual-ear one.

Replacing the subframe bushings might be enough to prevent the failure from occurring, or it might just forestall the inevitable. The theory has been around since about 2004-2005 and given the wide range of driving styles and past vehicle history, it's not 100% known if it's a perfect solution. It certainly seems to help.
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Old 04-13-2013, 09:30 AM
tjh54 tjh54 is offline
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Quote:
Originally Posted by vintage42 View Post
How many miles on the car, and how can you tell when the bushings need replacement?
It has 76k miles. For the past few weeks I have been hearing a clunck when going from reverse to first.
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Old 04-13-2013, 09:41 AM
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Quote:
Originally Posted by Blacklane View Post
The terminology gets a little vague since there isn't a good name for the part of the car that breaks. Technically, the Rear Subframe is the piece that mounts on each side of the car and holds the differential and the two Rear Trailing Arms. (It's the piece shown in you picture). The part that breaks is the unibody cross member that supports the differential mount or mounts, depending on which differential cover is installed.

You can find many threads here on the Randy Forbes reinforcing kit which strengthens the cross member and diff mount attachment. I've never seen him do a single-ear mount; I suspect he recommends replacing the diff cover with a dual-ear one....
So the rear subframe is actually the large part in the photo, and the Franks kit actually replaces the unibody cross member channel that is spot welded to the bottom of the trunk. But, the Franks kit is nevertheless called a rear subframe kit.

I hear the original single ear differential mount can be retained with the kit, if an extra new mount is bought to weld onto and reinforce the original. I would want to keep the single ear on the left of the differential, for several reasons. It retains the compact spare tire on the right, avoids having to buy a dual-ear differential cover, and is surely more than adequate for a 1.9L.

Last edited by vintage42; 04-13-2013 at 09:42 AM.
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Old 04-13-2013, 09:51 AM
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vintage42 vintage42 is offline
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Quote:
Originally Posted by tjh54 View Post
It has 76k miles. For the past few weeks I have been hearing a clunck when going from reverse to first.
I don't know if that means rear subframe bushings. I wonder if they would clunk from that shift and not from bumps. Maybe the sound could be as serious as the actual subframe channel loose under the trunk, or as minor as a bad guibo coupling.
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Old 04-13-2013, 09:58 AM
tjh54 tjh54 is offline
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Thanks so much for the help. This will make the job much easier and less expensive than I had thought.
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  #14  
Old 04-13-2013, 10:05 AM
tjh54 tjh54 is offline
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Quote:
Originally Posted by vintage42 View Post
I don't know if that means rear subframe bushings. I wonder if they would clunk from that shift and not from bumps. Maybe the sound could be as serious as the actual subframe channel loose under the trunk, or as minor as a bad guibo coupling.
I haven't driven it hard in over 8 years now. I think I'll get under it and give everything a good look. Thanks for the help.
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Old 04-14-2013, 05:43 AM
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vintage42 vintage42 is offline
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Quote:
Originally Posted by Blacklane View Post
The terminology gets a little vague since there isn't a good name for the part of the car that breaks. Technically, the Rear Subframe is the piece that mounts on each side of the car and holds the differential and the two Rear Trailing Arms. (It's the piece shown in you picture). The part that breaks is the unibody cross member that supports the differential mount or mounts, depending on which differential cover is installed....
I see that the big piece shown in the picture, that takes the bushings, is called Rear Axle Carrier in RealOEM:
http://realoem.com/bmw/showparts.do?...98&hg=33&fg=30

So if people called it that, there be no confusion with using Rear Subframe for the channel cross brace of the unibody. Instead of calling the bushings rear subframe bushings, they would be rear axle carrier bushings.
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