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Finalizing AWD-RWD Conversion with RWD Subframe Swap and M5/M6 Components

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Finalizing AWD-RWD Conversion with RWD Subframe Swap and M5/M6 Components

Old 04-01-2019, 11:02 AM
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My Ride: E61 with all the mods
Model Year: 2008
Engine: N54
Default Finalizing AWD-RWD Conversion with RWD Subframe Swap and M5/M6 Components

I figured this project was significant/interesting enough to warrant it's own thread. This isn't meant to be a DIY guide but I hope it's helpful as a reference. For more info on this build you can Google "Evan's E61."

Some of you might be familiar with my build, back in 2015 I started down the path of a RWD conversion when my front drivetrain was having a hard time handling the ~550awhp at my lowered ride height. For the sake of reliability and simplicity a RWD conversion seemed like a smart move. I loved the grip and poor weather capability of the AWD system but it was a ticking time bomb and I got tired of driving gingerly as to not hard the drivetrain.

The process started with pulling the front driveshaft, axles, disconnecting the TC actuator, and some coding. It was as step in the right direction but not a real solution. A manual swap was always on the radar so I went ahead and collected a RWD manual trans, all the necessary components for the retrofit, and upgraded the drivetrain to M5 everything with an MFactory SMFW, Spec Stage 3 clutch, upgraded trans and diff mounts. This setup necessitated a custom M5 dirveshaft and custom trans support. I also relocated the DSC pump and swapped the module to a unit from a 528i since they were compatible with 535is.

I never found success integrating the DSC pump into the car, there were some issues with the VIN and region since there were never RWD wagons in the US, or so we thought. The wagon was operational but DSC/ABS was in a default and non-functioning state since communication was broken between the systems.

My front subframe was the steel AWD unit and I hacked up my old axles, removed the outer CV cup with the splines, and used it with the 36mm axle nut to hold my spindles together. Not ideal but it worked.

The xi steering rack was a bit slow and I found myself annoyed when I would have to regrip the wheel during fairly standard 90 degree corners, it was obvious the steering wasn't up to par with the rest of the wagon.

Enter the M5 steering rack retrofit. Of course the xi subframe has a completely different architecture to accommodate the axles so to swap the AWD steering rack to an M5 unit required swapping the subframe and nearly all components which was everything minus the passenger side engine mount. lol

Here is a list of components I collected for the subframe swap
- Aluminum RWD Subframe
- M5 Steering Rack
- M6 Convertible Sway bar (thicker than M5 and M6 Coupe)
- KW V1 (RWD E61 Fitment, special order from Germany)
- 535i Power Steering Lines
- Engine Supports R/L
- Driverside Engine Mount
- RWD Spindles
- RWD Hubs
- M5 Control Arms
- End Links and brackets
- RWD steering shaft and firewall grommet

...that's it!

The main benefit of this conversion is the M5 steering rack but a nice bonus is the increased amount of room the RWD subframe offers, if you wrench a lot like I do that it's a significant improvement. For those of you who have never worked on AWD N54 cars consider yourself lucky, they are a pain.

The other bonus is the weight savings. Comparing the assembled AWD subframe to the aluminum RWD subframe, ~55lbs is saved.

AWD Subframe = 43 lbs
RWD Subframe = 20 lbs

AWD Spindles = 38 lbs
RWD Spindles = 12 lbs

-26 lbs of unsprung weight is a nice!

Adding this weight savings to what I have already saved with the AT-MT swap and deleting the other front drivetrain means the wagon has shaved 200+ lbs with the conversions although was added back with the beefier M5 components.

On to the photos, the first few are a recap of other RWD related parts which were installed.

M5 drivetrain

RWD manual trans vs AWD auto trans

Stock xi open diff vs M5 diff, M5 heatsink needed to be modded to fit wagon.

AWD oil pan up top vs RWD oil pan bottom

RWD configured motor going in

Motor in

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Old 04-01-2019, 11:03 AM
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My Ride: E61 with all the mods
Model Year: 2008
Engine: N54

Now onto the subframe conversion...

RWD subframe pulled from a 530i, it was 100F this day, not fun.

Steel AWD subframe for reference

RWD subframe cleaned up nicely after a power wash and some sanding

Started to collect parts

Removed my AWD KW V3 to test fit into the RWD spindle

No go

535i PS lines

535i pump/module

Fresh from Germany, KW V1 in RWD E61 fitment

With all parts on hand, time to go in

AWD subframe out

This pic shows how I used my outer CV cups to hols the spindles together

So much room for activities!

AWD engine mounts top, RWD mounts bottom. Although there is a subtle difference I believe the passenger AWD mount could have been reused.

Assembling RWD subframe

Removing steering shaft

AWD left, RWD right

Last edited by ucsbwsr; 04-01-2019 at 11:46 AM.
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Old 04-01-2019, 11:05 AM
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My Ride: E61 with all the mods
Model Year: 2008
Engine: N54

Ready for install

Not sure if Annie approves


Since I didn't swap my PS pump from 535xi to 535i I ran into an issue with hose fitment

Here is the 535i pump, it's identical to 535xi minus the dual threaded bolt the banjo fitting bolts to. The 535i bolt is much taller allowing the line to clear the pump

Ground down a chamfered to get the bolt out and further inspect.

Closer look at bolt assembly, I contacted LUK about individual parts and they said no dice, complete pumps only.

As opposed to spending time and money to sway the pump I decided to make it work and busted out the Dremel.

I FINALLY can run an M5 belly pan with the RWD subframe so my M5 bumper, fender liners, and belly pan all bolt up. Belly pan modified to clear intercooler. I love these OEM details.

Filling PS fluid

Swapping ABS/DSC pump. I previously relocated my pump from the engine bay to the OEM M5 location directly under the master cylinder, not sure why it wasn't this way from the factory.

New front pads and low mileage rears and new rear pad wear sensor.

Bleeding brakes, coding software on the garage TV FTW.

After some help from the coding wizard Levan, THANKS LEVAN!!!! my DSC pump was integrated and fully functional, no dash lights! Time for some celebratory revs and video proof of no lights!

I tried to take a WOT 2nd gear rip to show traction control kicking in but the wagon just hooked! lol M5 LSD and modest 285/35 Hankook V12s working well together

After the conversion was done I threw it on a scale, full interior, street spec with 1/2 tank of gas, happy to report I am sub 4,000 lbs. For fun I looked up the curb weight of an E61 M5 and as per the BMW's specs it's 4,310. For fun I made this comparison to highlight power to weight ratio, it's also a visual explanation as to why I chuckle when people ask if I am going to S85 swap it. Spend money to add weight and go much slower? No thanks! This gets the M boys all hot and bothered but that's ok, they need to learn to not be so defensive.

I refer to my wagon as an N54 powered M5, since that is the most accurate way of describing it since it has M5 everything minus the motor. There are a lot of people who think there is some magic wand BMW waves over M cars as they leave the factory and the reality is it is just some bolt on components that make the M cars M cars. You swap the components, you can make an M car, simple. "Yea, but the vin doesn't say M." Well, M cars are built to offer high performance and a dynamic driving experience, that is what matters to me, if you care more about the VIN number and M badges then you should reflect on your motives for buying an M car. Further more, if M cars can only be factory built with corresponding VINs and 100% original factory specs then that means any modification or upgrade you make your M car is no longer factory spec and therefore no longer an M car. You can't have it both ways lol.

S85 is a "special" race derived motor and offers a unique audible experience so I totally get why people love it and why they think it's an integral part of the "M" experience. But I like performance so the N54 was the choice for me. I know people will not agree with me and that's fine, keep enjoying your M5 (or buy one since they are dirt cheap) and I will continue to enjoy my wagon. Same team guys, same team!!

Last edited by ucsbwsr; 04-01-2019 at 11:47 AM.
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Old 04-03-2019, 08:57 AM
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Model Year: 2006
Engine: n52

as always bmw mechanics should watch and learn from YOUR SKILLS!!

What did u do with all the AWD COMPONENTS ?

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Old 04-09-2019, 07:33 PM
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My Ride: Alpine White E60
Model Year: 2009
Engine: N54 Cobb Tuned

Truly amazing the amount of time and effort you have spent to do everything so right including taking photos! Thank you for being so dedicated to the M5 swap!

Keep up the great work 👌
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