335i rear end rebuild - diff and subframe bushings question

carabuser

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So what started as a small job replacing all the control arms has become a fully fledged rear end rebuild.

I started out with a pile of M3 controls arms, the 4 up front and 6 in the rear (only 4 of them are the M3 ones, the rear arms are the 335i ones) along with some new trailing arms. I has also decided to rebuild all the calipers while I had the wheels off and also wanted to refresh all 6 brake lines. But upon inspection of the rear subframe I could see the diff leaking at the pinion seal and the brake lines were welded together since I live in an area that spreads salt in winter.

So after pulling all the control arms off the car I decided the proper way to proceed would be to drop the rear subframe so I could replace the hard brake lines that run along the top of the subframe and the 2 flex lines that are hidden away. I also need to fix the leaking diff so it seems like the common sense thing to do.

So while I'm in there I thought it would be a good time to replace the subframe bushings.

So my 2 questions:

1. Is it feasible to DIY the leaking diff? I've looked at a few threads and the BMW TIS info and I'll be honest, it looks a little painful. Part of me just wants to buy an LSD and just swap it over. (I don't actually want or need an LSD, this car will never see a track). Does anyone have experiences with leaky diffs?

2. Subframe bushings look like a PITA. I was planning on M3 bushings but the forums say that I should use Condor Speed UHMW bushings as they are better and also much easier to install. The internet says there's no downsides to these stiffer bushings, is this the right way forward for someone who isn't a racecar driver?

I'm going to be buying a load of parts and attempting to get this done over a long weekend, so any tips on useful tools or parts to change while in there would be much appreciated.
 
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carabuser

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Pic of my rusty rear end for attention. I hate this road salt bullshit.

I've already ordered completely new BMW hardware for everything I touch while in there. New hardlines, new ARB bushings and drop links.
 

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Jeffman

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Watching. I’m in the same boat for my 335xi. I also bought the Condor UHMWPE bushings, and the removal tool which I found on eBay for $70, as well as all of the other parts needed to redo my rear end. I also purchased more tools for removing and pressing in various bushings, etc. That was in 2021. Still looking for a long week to get it all done. Haha
 
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carabuser

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Watching. I’m in the same boat for my 335xi. I also bought the Condor UHMWPE bushings, and the removal tool which I found on eBay for $70, as well as all of the other parts needed to redo my rear end. I also purchased more tools for removing and pressing in various bushings, etc. That was in 2021. Still looking for a long week to get it all done. Haha
I had the control arms for a while, took time to build up the determination. Thought it was going to be a 2 day project, but every single bolt needs heat, the impact or the angle grinder.

I'm looking for local shops to take care of the diff. I like to DIY as much as I can but I've got enough headaches with the rest of the car.
 

pbondar

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I’m sure Birds near you could do the diff..they are tricky I gather even with the special tools…they could drop a Quaife in whilst they are there..you won’t regret it …
 

martymil

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Or just buy a complete m3 rear end and drop it in which will fix all the shitty design flaws of the 135/335

For example,

The tail shaft connection
the weak axels
all the bushing upgraded standard
better control arms
Lsd
stronger subframe
20mm narrower track for better wider wheel offset choice
better brakes

Much cheaper than upgrading individual components.
 

carabuser

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Or just buy a complete m3 rear end and drop it in which will fix all the shitty design flaws of the 135/335

For example,

The tail shaft connection
the weak axels
all the bushing upgraded standard
better control arms
Lsd
stronger subframe
20mm narrower track for better wider wheel offset choice
better brakes

Much cheaper than upgrading individual components.
Well, this is started due an advisory on one control arm having too much movement. I thought that I should probably take a look at all of them since it was relatively cheap to change them for TRW parts.

In hindsight, a complete M3 rear end would have been the better path since I'd have the M3 LSD. I still could go that route since I wouldn't want to fit a used subframe onto the car without changing all the control arms, and the parts I have are all the M3 replacements.

I'm never going to snap and axle in this car though, even if my stock turbos ever need replacing, I'll be staying below 500bhp.
 

CalvinNismo

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I bought a subframe bush removal tool from the States, it needed modification and I used it in conjunction with this eBay bush press kit. Pulled out standard M3 bushes fine, so regular non-M bushes should be easier still. That bush press kit can do all of the other suspension bushes including front and rear arms.

If you want to borrow the one from the States, let me know.
 

martymil

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The m3 axels and the whole m3 rear end is pretty much bulletproof, it only has one flaw they sometimes leak
from the pinion seal which is easily changed.

The m3 rear end is far superior to everything else and will also lift the value of your car.
 

carabuser

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The m3 axels and the whole m3 rear end is pretty much bulletproof, it only has one flaw they sometimes leak
from the pinion seal which is easily changed.

The m3 rear end is far superior to everything else and will also lift the value of your car.
Just pricing it up roughly, it's £2k for a well used M3 rear end, then I'd need a £1300 driveshaft because I wouldn't trust anyone in the UK to cut a weld the existing one without messing it up. I'd also need new brakes, discs, pads and probably dampers/springs too so costs are quite high for a car that is just for getting from A to B. I'm assuming I'd also need new wheels and tyres in the rear.

I'm also not sure about the gearing. Going from 2.56 to 3.15 on the DCT would be a headache. I can adjust the ratios in the TCU flash but I certainly don't want the RPMs any higher in 7th gear. The majority of the driving I do is long distance at 85-90MPH so it would be annoying having the engine at 4-5k rpm for long drives.
 

carabuser

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I bought a subframe bush removal tool from the States, it needed modification and I used it in conjunction with this eBay bush press kit. Pulled out standard M3 bushes fine, so regular non-M bushes should be easier still. That bush press kit can do all of the other suspension bushes including front and rear arms.

If you want to borrow the one from the States, let me know.
Thanks for the offer but I think shipping might be a killer. I was planning on melting and cutting the stock subframe bushes out since they are flimsy. The Condor ones will just press in as they are 2 piece.

The diff bushings were replaced a couple of years ago so will be fine. I was considering the other 2 bushings each side, the one that holds the lower spring perch and the other than holds the trailing arm. I might inspect them and see what condition they are in before replacing them. Otherwise I think I can get away without needing any of those bushing tools.
 

CalvinNismo

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Thanks for the offer but I think shipping might be a killer. I was planning on melting and cutting the stock subframe bushes out since they are flimsy. The Condor ones will just press in as they are 2 piece.

The diff bushings were replaced a couple of years ago so will be fine. I was considering the other 2 bushings each side, the one that holds the lower spring perch and the other then holds the trailing arm. I might inspect them and see what condition they are in before replacing them. Otherwise I think I can get away without needing any of those bushing tools.
It depends if you care about the paint if you are burning them out. It makes a right mess! A garage I used burned them out on a previous subframe.

No worries on postage, if you are anywhere near York, you are welcome to collect. Would be cool to meet an international SpoolStreet BNOC. 😂
 
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martymil

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All my cars run the m3 rear ends and front suspension. The 135i will too as soon as I get some time to swap it out inc the front hubs and brakes.

When you have experienced both in the same car you realise how substandard the stock crap is in comparison.
 

martymil

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Do what works for you but if one is starting from scratch I would source a complete setup and swap out the front/rear
suspension and brakes inc booster and master cylinder from a 1m/m3.

There are a lot more better upgrades and easier to source than the 135/335 stuff as in the end the m3 setup is what everybody is trying
to replicate in a roundabout way.

I understand your DCT final drive dilemma as in your case is the only draw back I guess.
 

carabuser

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I completely understand, the M3 components are really the way forward but for my usage I don't think it'll be worth the cost. Any M3 rear end I buy will need the diff rebuilding since the LSD requires it at the mileage I'm seeing, I'd also need to have the final drive altered so the cost starts to balloon.

One issue I'm anticipating is the removal of the driveshaft. I can see with the 335i I need a 50mm tool to remove the nut that holds the driveshaft. Would this tool work? https://www.ebay.co.uk/itm/403167858962
 
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carabuser

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It depends if you care about the paint if you are burning them out. It makes a right mess! A garage I used burned them out on a previous subframe.

No worries on postage, if you are anywhere near York, you are welcome to collect. Would be cool to meet an international SpoolStreet BNOC. 😂
I didn't realise you were UK based. Might take you up on the offer. I'll check out if I need it or not when I head back to the garage next weekend.
 

martymil

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Just remove the drive shaft and pumpkin as one if your budget conscious, just have to drop the mids and shield to remove.

Not sure on the tool, I just brought a cheap spanner from the local hardware and grinded down the sides to make it thinner to suit the stock
driveshaft.
 

AzNdevil

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dont you need a custom driveshaft + m3 diff + m3 rear shocks to do rear m3 subframe swap?
this is what drove me away from doing a full swap 6 years ago

honestly, if you are not road racing/drag, throw a used diff and m3 arms on and call it day...

personally speaking, the m3 diff might be stronger but diff engagement is worse than a mfactory helical, not worth the costs unless you are going all out to slap a os giken or drexler or something into the m3 pumpkin

and rear subframe bushings, poly bushings are so-so.... solid alu makes it feel a shit ton better...nvh is practically the same, and solid alu doesnt wear out so its lifetime ;) .................but its a pain in the ass to install

my vote goes to m3 arms, used diff, throw a diff brace on it

iirc someone on faceboook mentioned a f80 m3 driveshaft might fit for a m3 rear end swap, no idea, not confirmed
 
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Torgus

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I thought everyone was just buying ford 8.8s https://www.seemslegitgarage.com/product-page/E8xE9xFord88KitBundle ???

I kid.

The m3 swap is an option but not nearly are simple as some make it out to be(driveshaft) and it's not like the m3 bushings in the subframe are amazing. You will likely want to replace all the worn bushings in the subframe and arms anyways if you are going through all of of the hassle and while you are in there why not? The m3 diff is stronger than the stock Non M e9X diff but they have also had failures at high HP/TQ and as said above you really want to buy a quality diff for the m3 pumpkin or at a minimum rebuild the factory LSD. It all adds up quick.

Road salt is a bitch.

Edit: If you get a full rear m3 subframe with control arms now you need m3 rear specific suspension components(which is good) but you have to find a vendor willing to break up a m3 coilover/spring strut set etc. Which may not be easy. For instance I don't think Ohlins will sell the rears only anymore. Maybe you get a used set broken up(which most don'twant to do)? Or you ditch the better control arms and use your non m3 e9x control arms and suspension. The deeper you get into it the more the costs can/will add up.
 
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carabuser

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The M3 options is off the table for now. I do need to properly inspect the existing subframe, if the rust is anything deeper than surface rust then I'll consider replacing it.

I found a local garage that will reseal the diff. So I'll buy the seals and fluid then drop it over to them.

The rust issue is a bit confusing really. The front of the vehicle looks good, just some rust around the power steering lines. The rear is a mess.

My E89 has the same mileage and has been used for similar journeys and is spotless. Just some slight surface rust on the subframe. Maybe the first owner paid for some kind of rust proofing spray, or BMW just made the rear end out of better quality parts.