[jsunma]

I'm in the process of replacing the rear subframe for my 2008 E91 RWD. At 195K miles, mine is sufficiently rusted such that replacement makes sense. Obviously I'll freshen up all of the bushings back there at that time.

Anyway, my intention is to find a good used part and then paint and powder-coat it (for rust prevention over the original, uncoated metal, part). MY QUESTION is if anyone here can confirm the interchangability of different E-series rear subframes. Real-OEM claims that the part number for mine (33316783715) is exchangeable with nearly all E90s (sedans, coupes, converts, and wagons) from 2005 to at least 2011. The BMW parts sites I find say the same thing. This seems somewhat counter-intuitive, but I'd be willing to trust the info...EXCEPT some of the various salvage yards I've contacted beg to differ. They claim I need one specifically from a wagon (E91).

Obviously I don't want to pay someone to pull one from a car and then find out I've got the wrong thing, so I'm trying to see if anyone here with subframe experience has any info on exchangeability of these things.

Assuming that I really do have a range of cars to choose from to pull one from (and not "just wagons"...'cause frankly, those are relatively rare), I'd like to get one from as new a car as possible in an attempt to get one with the least rust and wear. So knowing what range I can deal with will help lots.

Thanks in advance for any info anyone might have!

[Tambohamilton]

They're all the same, so long as it's not an M3 part - those are different. Same part number = same part.

Some of the bolt on parts vary though; sway bar mainly, as well as springs and shocks. You can transplant your existing parts though, no bother.

[jsunma]

Originally Posted by Tambohamilton

They're all the same, so long as it's not an M3 part - those are different. Same part number = same part.

Some of the bolt on parts vary though; sway bar mainly, as well as springs and shocks. You can transplant your existing parts though, no bother.

Thanks for the info! So, just to be clear, the attachment points on the subframe are the same from model to model...it's just that (obviously) things like shocks, springs, etc. are different. Right?

[Tambohamilton]

Yep, exactly. The non-M rear subframes are all the same, regardless of e90/91/92/93.

[leif20]

What makes you think that it's too rusty? Are pieces literally falling off, or does the appearance make you think that? I think the subframe is quite thick, I wonder how bad it would have to be before it needs replacement.

[jsunma]

Originally Posted by leif20

What makes you think that it's too rusty? Are pieces literally falling off, or does the appearance make you think that? I think the subframe is quite thick, I wonder how bad it would have to be before it needs replacement.

Yeah, we had the car up on the lift the other day at my indy and you can actually see perforation. It's kind of scary. I think that pieces would literally be falling off if I decided to bang around on it.

That said, a non-rusty (or at least much more structurally sound) one from a parts car only runs between $150 - $200 (US). Labor to install it of course is many times that cost. I'd do it myself, but I think that this is a job that goes beyond jackstands and would just be faster with someone who's done it before.

(You can of course buy it new from BMW for around a grand. I love my car, but not that much...)

My indy said that this isn't that uncommon on high mileage/older cars like mine. He's seen it before on those rare occasions where he sees an E9X with nearly 200K on it like mine. The part is pretty much uncoated from the factory, and they use what seems like battery acid on the roads down here in the winter. If I had it to do over, I would probably have started using that annual oil-based undercoating stuff that is becoming increasingly popular here in New England.

[TDF9]

Hi there.

I have pretty scary rust on my rear subframe, too (2006 325i w/ 210k miles, New England miles) - and had the same idea (buy a used one, repaint it, swap out the rusty one for new used one).

Curious what sort of cost estimate your mechanic has given to do the job? I'm considering doing this myself - but without a lift, and given all that's involved, am curious to know how much it would cost to have a professional do it.

[jsunma]

Originally Posted by TDF9

Hi there.

I have pretty scary rust on my rear subframe, too (2006 325i w/ 210k miles, New England miles) - and had the same idea (buy a used one, repaint it, swap out the rusty one for new used one).

Curious what sort of cost estimate your mechanic has given to do the job? I'm considering doing this myself - but without a lift, and given all that's involved, am curious to know how much it would cost to have a professional do it.

You're in Wayland? The place I will use to do this job is in Tewksbury...maybe we can get a package deal if they do both our cars.

I actually don't have the final estimate yet, but I'm expecting it to be around a grand including the parts. It won't be cheap...but given that this is the only issue that the car has, it's worth it to me to address it. I'll post here once I know.

[Timothi2]

Kind of a late response, but just agreeing with what others have said. I have an n54 swapped e91 wagon, and I swapped all of the 335i suspension including subframes and quite literally everything into my 328i wagon. The subframe is actually exactly the same between all of the different chassis e90, e91, e92 and e93. I actually have my 328i subframe lying around since I finished the swap, it's got 112,000 miles on it but it's practically in perfect condition as it came from California so it hasn't seen very much harsh weather at all. PM me id you're interested? I have all of the 328i rear suspension bits still connected to it as well.

In terms of the swap, it's actually a piece of cake labor wise. I did it by myself with my wagon on jackstands. Only thing holding the rear subframe to the car is the brake lines, e brake cables, the 4 main subframe bolts, strut tops, and 2 more bolts on each side near the front of the subframe attaching it to the body. It sounds more complicated than it really is, wish I took pictures while I was pulling mine off so I could have done a diy

[TDF9]

Originally Posted by jsunma

You're in Wayland? The place I will use to do this job is in Tewksbury...maybe we can get a package deal if they do both our cars.

I actually don't have the final estimate yet, but I'm expecting it to be around a grand including the parts. It won't be cheap...but given that this is the only issue that the car has, it's worth it to me to address it. I'll post here once I know.

Thanks - like the 2 for 1 idea! Good luck and let me know. I have a great independent mechanic here in Natick - Farley @ Eurosport - but just imagine hours of work to transfer all the rear links, drive axles, brakes, shocks, diff, etc. And there are the bushings to deal with.

[TDF9]

Originally Posted by Timothi2

In terms of the swap, it's actually a piece of cake labor wise. I did it by myself with my wagon on jackstands. Only thing holding the rear subframe to the car is the brake lines, e brake cables, the 4 main subframe bolts, strut tops, and 2 more bolts on each side near the front of the subframe attaching it to the body. It sounds more complicated than it really is, wish I took pictures while I was pulling mine off so I could have done a diy

Wow, very curious to hear that - just imagine hours to move everything from old subframe to new. I'd be interested in your best guess of how much time it took...

[Timothi2]

Originally Posted by TDF9

Wow, very curious to hear that - just imagine hours to move everything from old subframe to new. I'd be interested in your best guess of how much time it took...

I pulled it off as one big assembly, suspension and all. Total, I'd say it probably took me about 2 hours to drop the entire subframe as one giant piece. Then I'd estimate it would take you probably about 30-40 mins to swap all the suspension bits, it's super easy once the whole subframe is out of the car. Then roughly another 2 hours to get it back into place and bolted in. It's really helpful to have two people for this last part to guide it back into it's proper place. If you know what you're doing mostly, you could get the entire job done in about 6 hours total. If I had to do it again, I could probably get the whole thing done in about 3-4 hours

[mweisdorfer]

How much is a new one vs buying a used one. If you buy a used one, make sure it's from a southern, non-salt in the winter state.

[jsunma]

Originally Posted by mweisdorfer

How much is a new one vs buying a used one. If you buy a used one, make sure it's from a southern, non-salt in the winter state.

A new one - BMW original part of course - is around $1000. I've seen them at ECS and FCP. They're available. A used one, from a salvage yard, is about $150. That's for JUST the frame (although in most cases they'll probably contain the frame bushings I suspect). I think that one reason why they're not that expensive used is that it's not a frequently used part. Consensus from people I've spoken to (including here in this thread) is that they're honking big pieces of steel and really don't rot to the point where people go changing them...at least not until many years and miles have elapsed.

Which is kind of where I am right now. I've had additional folks look at mine and have had the chance to really bang around on it, and can see that it's not really "rusted through"...just very crusty in spots. I do think that I will eventually want to replace it and with more miles will likely at that time want to have better/new bushings to help tighten up the car's rear-end. But as a basic safety issue, I don't think it's going to break. I will probably brush off the rust/crust this fall and treat the clean(er) metal to give it the best chance of life. And then maybe next summer.... The idea developed here in this thread that it's not really such a difficult job is very very promising.

At least that's what I'm thinking at the moment as Fall rapidly approaches and the various projects (car related and not) keep piling up. Thanks though for all of the good info offered by folks here!

[mweisdorfer]

Originally Posted by jsunma

A new one - BMW original part of course - is around $1000. I've seen them at ECS and FCP. They're available. A used one, from a salvage yard, is about $150. That's for JUST the frame (although in most cases they'll probably contain the frame bushings I suspect). I think that one reason why they're not that expensive used is that it's not a frequently used part. Consensus from people I've spoken to (including here in this thread) is that they're honking big pieces of steel and really don't rot to the point where people go changing them...at least not until many years and miles have elapsed.

Which is kind of where I am right now. I've had additional folks look at mine and have had the chance to really bang around on it, and can see that it's not really "rusted through"...just very crusty in spots. I do think that I will eventually want to replace it and with more miles will likely at that time want to have better/new bushings to help tighten up the car's rear-end. But as a basic safety issue, I don't think it's going to break. I will probably brush off the rust/crust this fall and treat the clean(er) metal to give it the best chance of life. And then maybe next summer.... The idea developed here in this thread that it's not really such a difficult job is very very promising.

At least that's what I'm thinking at the moment as Fall rapidly approaches and the various projects (car related and not) keep piling up. Thanks though for all of the good info offered by folks here!

Spray paint it with rustoleum primer & paint once you treat it with an anti-rust solvent.

[TDF9]

Reviving this thread as I've started replacing the subframe on my 325i. Finally got it out tonight, after painful process to get parking brake disconnected and brake hoses loose (corrosion is out of control), and have a few questions I hope someone can help with:

1) must I replace the bolts that hold the subframe to the body? I can't tell if they're aluminum. Prefer not to drop $40 on these if not. Any other bolts I should be sure to replace?

2) any advice about how to decide which bushings are shot and need replacement - and/or, which are highest impact to refresh? I'd originally thought I'd do as many as possible, but I'm now appreciating how much time, cost and hassle that'd be. I'm thinking the Whiteline subframe inserts make sense (and far easier than replacing the subframe bushings), and I've read the trailing arms take a lot of abuse, so thinking they're my next highest priority. Beyond that... just not sure. No obvious clunks or odd noises coming from the back of the car, but it'll also easily deflect off its line if I hit a bump mid-corner.

3) should the shocks rebound quickly when compressed? With the subframe out I compressed the shocks by hand and was surprised they take seconds - 5+ or so? - to rebound. Curious if that means they're done. Previous owner replaced them, but that might've been 50k miles ago.

4) the brake hose to solid metal line connections - both on the subframe and on the body of the car - are incredibly rusty and corroded. I'm concerned metal lines on the body will be damaged when I try to remove the hoses. Anyone have special tricks to avoid this?

I appreciate all thoughts and advice!

[mweisdorfer]

Originally Posted by jsunma

I'm in the process of replacing the rear subframe for my 2008 E91 RWD. At 195K miles, mine is sufficiently rusted such that replacement makes sense. Obviously I'll freshen up all of the bushings back there at that time.

Anyway, my intention is to find a good used part and then paint and powder-coat it (for rust prevention over the original, uncoated metal, part). MY QUESTION is if anyone here can confirm the interchangability of different E-series rear subframes. Real-OEM claims that the part number for mine (33316783715) is exchangeable with nearly all E90s (sedans, coupes, converts, and wagons) from 2005 to at least 2011. The BMW parts sites I find say the same thing. This seems somewhat counter-intuitive, but I'd be willing to trust the info...EXCEPT some of the various salvage yards I've contacted beg to differ. They claim I need one specifically from a wagon (E91).

Obviously I don't want to pay someone to pull one from a car and then find out I've got the wrong thing, so I'm trying to see if anyone here with subframe experience has any info on exchangeability of these things.

Assuming that I really do have a range of cars to choose from to pull one from (and not "just wagons"...'cause frankly, those are relatively rare), I'd like to get one from as new a car as possible in an attempt to get one with the least rust and wear. So knowing what range I can deal with will help lots.

Thanks in advance for any info anyone might have!

Find a place that can sand blast first & then power coat it. I can't imagine that costing more than $300.00

[Tambohamilton]

Good shout. Media blasting is probably the best way to actually remove the rust. If you do get it powder coated, get them to apply a zinc primer first

[ckegman]

Been reading because getting ready to drop subframe on my 2011 328i. Putting brand new factory subframe back in, when it is down. I will be replacing control arms, trailing arms the works. Has been my commuter car for 10 years of enjoyable driving commutes 1 1/2 hrs. each way. Last year some one hit me not hard but just right where my right rear is tweaked drivable but wears tire. Just 10 years driving in north winters and all the salt. Everything seems to be a pain with corrosion. Lucky me I recently retired and can take my time. Been changing everything water pump, thermostat and all new hoses, brakes rotors starter alt and so on. Just did M3 control arms, complete front end. So rear is the last thing left. I was thinking about DYI doing it all. On shocks how hard are they to compress?

[TDF9]

Originally Posted by ckegman

Been reading because getting ready to drop subframe on my 2011 328i. Putting brand new factory subframe back in, when it is down. I will be replacing control arms, trailing arms the works. Has been my commuter car for 10 years of enjoyable driving commutes 1 1/2 hrs. each way. Last year some one hit me not hard but just right where my right rear is tweaked drivable but wears tire. Just 10 years driving in north winters and all the salt. Everything seems to be a pain with corrosion. Lucky me I recently retired and can take my time. Been changing everything water pump, thermostat and all new hoses, brakes rotors starter alt and so on. Just did M3 control arms, complete front end. So rear is the last thing left. I was thinking about DYI doing it all. On shocks how hard are they to compress?

I did mine last summer and don't recall compressing the rear shocks to be an issue at all. I lifted the subframe back up into the car on a hydraulic jack, and just guided the shocks into the lower mounts. Good luck!

[ACJBMWPVD]

Originally Posted by Timothi2

Kind of a late response, but just agreeing with what others have said. I have an n54 swapped e91 wagon, and I swapped all of the 335i suspension including subframes and quite literally everything into my 328i wagon. The subframe is actually exactly the same between all of the different chassis e90, e91, e92 and e93. I actually have my 328i subframe lying around since I finished the swap, it's got 112,000 miles on it but it's practically in perfect condition as it came from California so it hasn't seen very much harsh weather at all. PM me id you're interested? I have all of the 328i rear suspension bits still connected to it as well.

In terms of the swap, it's actually a piece of cake labor wise. I did it by myself with my wagon on jackstands. Only thing holding the rear subframe to the car is the brake lines, e brake cables, the 4 main subframe bolts, strut tops, and 2 more bolts on each side near the front of the subframe attaching it to the body. It sounds more complicated than it really is, wish I took pictures while I was pulling mine off so I could have done a diy

I am interested in an N54 swap into my e91....why did you swap the subframes if they are all the same?

I simply want to get the motor/electronics and manual trans and plug it into my transfer case.

I am an experienced DIY mechanic with full size trucks (restorations, monster horsepower builds, cummins swaps, axles, lifts, trans, coding...so im no noob in the garage) , but im not experienced with e90 chassis outside of performing maintenance and simple modifications to this platform.

[Timothi2]

Originally Posted by ACJBMWPVD

I am interested in an N54 swap into my e91....why did you swap the subframes if they are all the same?

I simply want to get the motor/electronics and manual trans and plug it into my transfer case.

I am an experienced DIY mechanic with full size trucks (restorations, monster horsepower builds, cummins swaps, axles, lifts, trans, coding...so im no noob in the garage) , but im not experienced with e90 chassis outside of performing maintenance and simple modifications to this platform.

The subframes are the ONLY thing that are the same between the 328i and 335i. Axles, rear diff, driveline, brakes, all that is different. Instead of taking everything apart and swapping it over, I dropped the entire rear subframe assembly with everything connected and bolted the entire assembly onto the wagon. That way I only had to unbolt a few things instead of taking everything off individually.

What you want to do will work, though you might run into issues with the driveline length being different. The transmissions are different sizes between the n52 and n54, and the driveline flange is different too from what I recall.