[Efthreeoh]

Originally Posted by Dave92N54

It's weight savings and metallurgy for the most part. Steel bolts and an aluminum block (N54, Magnesium/Aluminum composite for N52) do not go well together. What happens is electrons will transfer from the aluminum into the steel, weakening the aluminum.

Personally i'd take the much, much lighter aluminum subframe paired with bolts that need to be replaced than an incredibly heavy subframe so we can use steel bolts. I'd have to say as for the japanese, that's only true of older ones. Toyota uses lots of aluminum these days.

It's very interesting to see other manufacturers taking cues from BMW, and the other germans. It's almost like they wait a few years and start doing the same. For example, If you were to set a modern chevy coolant hose next to one of ours, you'd probably think they both came off a BMW. Same with the valve covers, water pumps, etc.

The subframe bolts are steel, not aluminum. The only place aluminum bolts on the E90 is on the N52 magnesium engine block. Steel bolts threaded into aluminum is not a galvanic issue per se'. Since the auto industry has gone with mostly all aluminum engine blocks, steel fasteners continue to be used in most all applications.

Road salt is what reacts with the aluminum on an automobile.

[3PedalJake]

I found a motorcycle/ATV jack works great for removing/installing subframes at jackstand height because it has a big enough footprint you can block it up all over underneath for support and raise/lower it straight up and down. I also reused all my bolts after cleaning and treating them with RPM.

[Efthreeoh]

Originally Posted by 3PedalJake

I found a motorcycle/ATV jack works great for removing/installing subframes at jackstand height because it has a big enough footprint you can block it up all over underneath for support and raise/lower it straight up and down. I also reused all my bolts after cleaning and treating them with RPM.

Dude, that diff is just too clean and pretty.

Just sayin'

[3PedalJake]

Originally Posted by Efthreeoh

Dude, that diff is just too clean and pretty.

Just sayin'

It really is. I created a problem for myself by making it so immaculate that I was only able to solve by getting a whole other car to actually use. The 330i mostly lives in the garage and only comes out on dry days with no chance of puddles to destinations with no shopping carts and tight spaces.

[Efthreeoh]

Originally Posted by 3PedalJake

It really is. I created a problem for myself by making it so immaculate that I was only able to solve by getting a whole other car to actually use. The 330i mostly lives in the garage and only comes out on dry days with no chance of puddles to destinations with no shopping carts and tight spaces.

BMW one day is going to call both you and me. Yours for a museum piece. Mine for durability analysis.

[3PedalJake]

Originally Posted by Efthreeoh

BMW one day is going to call both you and me. Yours for a museum piece. Mine for durability analysis.

That would be cool, because by the time I'm fixin to croak and be done with it I don't believe there will be anyone left who knows how to row a MT. I'm already feeling like it's a fairly effective anti-theft device.

For you it's what, @ double the mileage you were at when you first made Hans & Fritz scratch their goatees with a high mileage issue? I found it interesting an article I ran across while researching CBS system, where one of your posts is used as an argument that Bimmers are disposable cars. Everything BMW I search for ends up leading back to this forum.

https://www.thetruthaboutcars.com/20...es-disposable/

[Efthreeoh]

Originally Posted by 3PedalJake

That would be cool, because by the time I'm fixin to croak and be done with it I don't believe there will be anyone left who knows how to row a MT. I'm already feeling like it's a fairly effective anti-theft device.

For you it's what, @ double the mileage you were at when you first made Hans & Fritz scratch their goatees with a high mileage issue? I found it interesting an article I ran across while researching CBS system, where one of your posts is used as an argument that Bimmers are disposable cars. Everything BMW I search for ends up leading back to this forum.

https://www.thetruthaboutcars.com/20...es-disposable/

Holy crap! Ironic that one of the BMW E90 owners who takes a bunch of shit on this Forum (see recent other threads on OCI as an example) for espousing how great and long-lasting the E90 is, some BS car forum "The Truth About Cars" uses my 2013 CBS experience as evidence "BMW makes disposable cars". LOL.

I'm logging into that forum to provide an "Update"

Thanks for pointing it out.

[cmbe92guy]

Originally Posted by NGEE

The sub-frame just has holes in it that the bolts pass thru - so maybe you meant new frame?



I have solved the problem and got it all zipped back up. Only set me back a week

First I purchased the Schwaben thread chaser set ($32 at ECS). This type of tap does not cut - only cleans. I believe it is meant to be used in a situation where threads are simply corroded but not mangled. Or situations where you can thread it into good threads on one end, and clean the bad threads on the other end as you run it through. Not the case here and I could not get it to bite into anything.

Then I ordered an Irwin tap and die set with a 12x1.5 tap ($100 at Amazon). I ran the tap in, at first just wanting to try and tap the bad threads but not go all the way in and re-tap the good threads. As I suspected, the transition from bad, re-cut threads to good original threads was not clean. So I ended up running the tap all the way in. That worked.

I also figured out why the damn thing probably got cross-threaded to start with. My sub-frame may be warped or otherwise out of alignment. When I tighten the two fore bolts and the two middle bolts, the two rear bolts should line up perfectly with the frame bushings. But while the left side rear of the sub-frame is tight and aligned with the frame bushing, the right side is drooped down. At any rate, when I tried to run the bolt up into the newly-cut threads, it would not go. It was binding on the hole in the sub-frame, which wasn't 100% aligned with the bushing. I would drop the sub-frame and verify that the bolt would hand-thread cleanly. But when I tried to reinstall the sub-frame, it would bind. I actually ended up cutting the sub-frame hole a bit larger using an electrician's step-bit, and then the bolt ran in like a champ.

I torqued all the bolts to 80 ft lbs, except the re-threaded one which I just ran in PDT.

Thanks everyone for the inputs.

Thank the lord for this thread. I’ve found myself in a similar position. Swapping the trans and wanted to drop subframe for some extra room- I think I zipped out the two rear bolts last. Now the bottom 30-45% of the right rear subframe bolt threads are mangled.

I tried a 12x1.5 thread chaser to no avail, as you did. Just to be clear, your fix was to run a 12x1.5 thread TAP through? How did the threads look after this? As you mentioned, it seems counterintuitive to run a thread tap of the same size.

Looking forward to your input. This 8hp swap has been fairly straight forward aside from msc ‘side quests,’ like this one. Throwing in the towel for tn.

[NGEE]

Originally Posted by cmbe92guy

Thank the lord for this thread. I’ve found myself in a similar position. Swapping the trans and wanted to drop subframe for some extra room- I think I zipped out the two rear bolts last. Now the bottom 30-45% of the right rear subframe bolt threads are mangled.

I tried a 12x1.5 thread chaser to no avail, as you did. Just to be clear, your fix was to run a 12x1.5 thread TAP through? How did the threads look after this? As you mentioned, it seems counterintuitive to run a thread tap of the same size.

Looking forward to your input. This 8hp swap has been fairly straight forward aside from msc ‘side quests,’ like this one. Throwing in the towel for tn.

Yes, that's what I did. Your experience may vary!

It's been a while and the car is gone, along with my memory of much of it. But my threads got mangled during install, whereas it sounds like your threads may have got mangled during uninstall.

One thing that's a SUPER important lesson-learned for me is running all six bolts in by hand BEFORE attempting to install the subframe - this verifies that the bolts/threads are in good shape and that you should not encounter any resistance. With this knowledge, you then know that if you do encounter resistance, you have a problem. STOP, realign the subframe, and proceed again until all six bolts thread in mostly by hand.

In my case, after fixing the damaged threads in the body frame, I verified that all six bolts ran in cleanly by hand. However no matter how many variations of alignment I tried, I kept meeting resistance in that last hole because the subframe kept binding the bolt. Widening that last bolt hole in the subframe did the trick by giving me a bit more play to eliminate the binding. Then I was able to run the bolt in clean.


Good luck.

[cmbe92guy]

Originally Posted by NGEE

Yes, that's what I did. Your experience may vary!

It's been a while and the car is gone, along with my memory of much of it. But my threads got mangled during install, whereas it sounds like your threads may have got mangled during uninstall.

One thing that's a SUPER important lesson-learned for me is running all six bolts in by hand BEFORE attempting to install the subframe - this verifies that the bolts/threads are in good shape and that you should not encounter any resistance. With this knowledge, you then know that if you do encounter resistance, you have a problem. STOP, realign the subframe, and proceed again until all six bolts thread in mostly by hand.

In my case, after fixing the damaged threads in the body frame, I verified that all six bolts ran in cleanly by hand. However no matter how many variations of alignment I tried, I kept meeting resistance in that last hole because the subframe kept binding the bolt. Widening that last bolt hole in the subframe did the trick by giving me a bit more play to eliminate the binding. Then I was able to run the bolt in clean.


Good luck.

I used a thread chaser as a makeshift tap. Was able to torque the bolt down to 80ft/lbs like normal. Lesson learned: remove the two rear subframe bolts 1st and install them last.

Thanks for your help.

[Bims328i]

Super helpful tips for dropping the subframe! I am really good about getting fasteners in properly but I'm trying to gather up a lot of information before I try to tackle my OPG.

After reading this thread I'm left thinking if it would help to make a wood 2x4 setup for your floor jack to support the subframe. Mainly just a basic form fit to apply force more evenly.