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      02-11-2021, 12:07 AM   #1
chocstraw
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Front Subframe Replacement

So with the recent rains here in California, despite my best care, I hit a very large rock, about 10" in diameter. Aside from cracking my 359M, it also cracked part of my subframe. Minor paint chips to a bumper that already needed a repaint, and shockingly no damage to any suspension components or anything else.

I managed to source a perfect used subframe less than 20 mins from me for $350 and I'm debating just installing it myself. I'll have access to about 2' of clearance underneath for the front, a transmission jack, and have all the hand tools necessary.

I will likely undo all of the control arms and the tie rods, etc, and just allow them to hang from the strut tower / wheel hub while doing this, then bolt them back up to the new subframe.

Questions:

-Do I have to drain the power steering or will I be able to unbolt it and just move it out of the way?

-any lines or wires in the way or any special things to know?

I've purchased the 4 stretch / torque to yield bolts for the back 'wings' of the subframe to go along with the install, but other than that, it seems that the bolts will be reusable.

book hours are 7.2. Anyone that has done a DIY rod bearing job would be of immense help.

Thanks
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      02-11-2021, 07:38 AM   #2
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Sorry to hear about your car. I hit a rock the other day that scratched my slon dct pan and I was annoyed. I also was unable to dodge it.

It sounds like a DIY rod bearing job, only easier.
You don't have to remove the oil pan
You follow the steps until the subframe is hanging, then continue to remove things. I think you'll have to remove the steering rack but not certain.

All in all this is not a nightmare job. You can do it on jack stands if necessary

Good luck!
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      02-11-2021, 09:10 AM   #3
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Don't forget you need an engine support bar.

Can be done at home. I did it without disconnecting the steering rack. But it was way too much fiddling and technique to slip the subframe out with it in place.

So I would recommend get the washers for the bango connection and let it drain. I have to do that anyways this year as I want to replace the steering fluid.

I hate dealing with hydraulic systems and worry about bleeding air out after. So it's why I avoided it.
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      02-11-2021, 11:41 AM   #4
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DIY it, disconnect all arms and swing them out of the way, disconnect the two PS banjos when you lower the subframe and pull the whole unit out, swap the rack over outside of the car.
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      02-11-2021, 12:10 PM   #5
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https://www.bimmerpost.com/forums/sh...php?p=24939273

Here's a good guide
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      02-11-2021, 02:53 PM   #6
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Quote:
Originally Posted by amrazM View Post
DIY it, disconnect all arms and swing them out of the way, disconnect the two PS banjos when you lower the subframe and pull the whole unit out, swap the rack over outside of the car.
to clarify, this does involve draining the PS?

yes it does, 2 liters of CHF11S on the way too

Last edited by chocstraw; 02-11-2021 at 10:11 PM..
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      02-12-2021, 06:57 PM   #7
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Quote:
Originally Posted by ha9981 View Post
Don't forget you need an engine support bar.

Can be done at home. I did it without disconnecting the steering rack. But it was way too much fiddling and technique to slip the subframe out with it in place.

So I would recommend get the washers for the bango connection and let it drain. I have to do that anyways this year as I want to replace the steering fluid.

I hate dealing with hydraulic systems and worry about bleeding air out after. So it's why I avoided it.
non-reusable crush washers? So glad I live near pelican parts
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      02-12-2021, 07:56 PM   #8
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Have to support the engine from above.

Also you don't have to remove the steering rack. If you have some patience you can work the subframe off and keep it all intact. Did it twice, once when i rebuilt the car (bought it salvage) and when I did rod bearings. I had access to a two post and just was easier to get it off and do the work.
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      02-22-2021, 03:44 PM   #9
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Aside from some slight weeping from the PS, the repair went well enough. One last question:

the wheel isn't quite centered, it is angled slightly to the right.

Is this an issue of aligning the U-Joint spline or can this be fixed with an alignment?
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      02-22-2021, 07:50 PM   #10
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You can redo the u joint spline, remove steering wheel and recenter, or realign. If you think the issue is alignment related, Id try that first.
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      02-22-2021, 09:08 PM   #11
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Quote:
Originally Posted by chocstraw View Post
Aside from some slight weeping from the PS, the repair went well enough. One last question:

the wheel isn't quite centered, it is angled slightly to the right.

Is this an issue of aligning the U-Joint spline or can this be fixed with an alignment?
Did you mark where the spline was removed?

You can try to remove and adjust it a teeth or two. But if you have no original marker it is harder.

Otherwise getting an alignment will get your issue fixed. I didn't have this issue but I've read others who either moved the spline position to fix it or got an alignment done.
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      02-22-2021, 09:26 PM   #12
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I did mark it but it's difficult to tell when the joint is in such a tight place.

it's a keyed version so I figured it could only go in one way
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      02-23-2021, 06:52 AM   #13
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I think the key is great. I have other cars in which there is no key. I tend to think you moved the wheels a little when the rack was disconnected. The locators for the subframe are pretty snug.
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      02-23-2021, 06:51 PM   #14
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Definitely do an alignment after dropping the subframe. Everything will never go back perfectly.
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      02-23-2021, 07:29 PM   #15
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Quote:
Originally Posted by tdott View Post
Definitely do an alignment after dropping the subframe. Everything will never go back perfectly.
I was definitely planning on a toe alignment but it's about ~10 degrees off which seems excessive.
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