[N111CUK]

335i project M3

Now before I start let me just answer the question most people put to me. Why don’t you just buy an M3? Well because I prefer the N54 engine the 6AT transmission and how it drives daily. I also believe this car can make a great weekend arrive and drive track car and overcome its heating issues.
What mods on my the 2007 335i 6AT M Sport

• Vishnu Procede V5 £500
• Vishnu PWM Methanol Injection trunk mounted £800
• PLM 3” De cat Down Pipes £200
• Custom cat back exhaust using OEM back box £400
• Injen Dual Cone Intake £200
• Spearco FMIC £300
• HEL braided brake lines £95
• M3 Rear sub frame including disks brakes hubs etc.. £500
• M3 Front brakes with M3 hubs and carriers £150
• KW V3 coilovers M3 spec £1450
• H&R Anti Role Bar Front £75
• Original Cost of Car £14,000

Total spend £18,670

The main mod which is of most interest is my M3 rear sub frame transplant
The complete M3 sub frame fits 100% into the 335i and requires a modification to the Prop shaft.

Why use an M3 rear instead of the Quaife? Well this route IMHO is better as I get all the clever suspension bits from the M3, stronger axles and prop including better brakes and for less money.

I must offer my gratitude to another e90post member IDNAN who had already completed this conversion before and helped me overcome some major questions. THANKS!

ALSO a big thanks you to MVG Engineering in Dartford Erith for all their help in getting this Installed. 01322 342699 speak to John he is very knowledgeable

Combinations of parts for the M3 Differential install

• M3 E92 DCT Rear sub frame with FD of 3.15
• M3 E92 DCT Prop shaft
• 335i 6AT Prop Shaft

As I mentioned before the sub frame is a straight fit. The considerations you will have to take into account are the final drive of the differential you choose.

335i gearbox transmission ratios
• 335i 6MT OEM Diff gearing FD 3.08
• 335i 6AT OEM Diff gearing FD 3.46
• 335i DCT OEM Diff gearing FD 2.56
M3 gearbox transmission ratios
• M3 6MT OEM Diff gearing FD 3.85
• M3 DCT OEM Diff gearing FD 3.15

Now armed with this information you can decide what FD you end up with. Choosing a lower number than your OEM setup will give you longer gearing and picking a higher number than OEM will shorten you gearing. This will not throw up any CEL codes but will be important to overall performance output.

I picked the DCT M3 diff as this would lengthen my first gear which was a little short IMHO and means my 1 gear launches are more usable with all the performance mods. I also can cruise on the motorway freeway at lower revs and higher speeds improving MPG.

If you have a DCT 335i and install a 6MT M3 diff you would be way out and you could take off in 3rd gear which would be crazy. I would go with as close a ratio as OEM and maybe go longer if you have mods making the car more powerful with more torque.

Now once you have the Diff you need to modify the prop. You could get a new prop built but so long as you have the M3 prop you can use this with your OEM prop and create a new prop for this application.

The best way to create the new prop is to combine the 335i prop and the M3 prop. Use the 335i tri bolt flange plus gimbal plate (rubber bushing with 6 holes) and the 335i centre bearing(this is vital to keep everything in line as intended by BMW OEM). You then mate this to the M3 prop creating a very strong custom prop which is mostly M3 but is 100% OEM fit.

Measuring this was simple. The measurements are split into two parts.
1. Diff to Centre bearing
2. Centre bearing to Transmission

The first measurement on the M3 prop is spot on. This part of the M3 prop remains constant because we share the same monocot chassis as the M3. What we need to measure for cutting and attaching is the second measurement. This measurement is from Centre Bearing bolt hole to rear side of the tri bolt flange. To get this absolutely right you should provide the prop builder both of the measurements because they will need to remove the centre bearing and attach the 335i bearing and therefore they need to know where all three points will be in relation to each other.

What I did was to attach the 335i prop to the transmission (make these bolts tight) and centre bearing (locate only one bolt) and take a measurement from the centre bearing bolt hole (one without the bolt) to the face of the flange attached to the 335i prop (your tape measure will be at an angle that’s OK). Then once you have this take it off and attach the M3 prop to the diff and then to the centre bearing again put all 6 bolts tight on the diff and only one bolt in the centre bearing. Then take another measurement. You now have both measurements for the Diff builder. Get a good shop to make this up for you. I used JW Engineering in Erith Dartford, they build racing props for kit cars and touring cars so they know there stuff.

NOTE: It is important to understand at this point that any prop has expansion movement at one of its halves; the 335i prop has movement at the front portion near the transmission where by the M3 prop has its movement at the rear at the diff. You should only keep one movement when building a prop
Some other challenges and choices that comes to light when doing this.

1. The M3 rear sub frame comes with all the M3 suspension arms etc.. (GREAT!!) but this also means you need M3 shocks and Springs as the 335i shocks won’t fit . At this point I decided to get new coil overs and opted for KW V3. I ordered the M3 version.

2. Now you have M3 rear brakes they are actually bigger in diameter than the 335i fronts and also drilled. You could just keep the 335i fronts but I opted to keep the OEM theme here and get some cheap M3 front Disks Callipers hubs and Carriers. This also makes the M3 KW coil overs fit. So I’m stopping a lot better now.

3. Depending how your sub frame turns up you may need some extra bits from the dealer. Bolts were the main bits that I needed. Prop bolts, Calliper carrier bolts, M3 Rear spring lower bushings, M3 Front strut plates etc….
The whole project took a week but with better planning and this info I’m providing you could get this done in two days tops. I had a lot of stop starts as I would run into a parts shortage or the above challenges and I needed to stop working.

What’s she like to drive. Well I can say that it’s better than the OEM M3 and very committed into corners. Traction is never an issue and no noises or issues with the conversion. If I had gone the Quaife route I would have not gained better breaks suspension and M3 components so I think I got a better deal and car in the long run.

The car is no wider at the rear than with the 335i rear sub frame so no concerns with wheel clearance.

I’ll try and help any of you guys with this conversion you may want to take your own route to complete this.

Thanks for reading my post all the best
Adam




I'll post loads of picks when I can

[JonD]

What are you actually selling

[Nigelo]

Oops with the thread location!

I might need your help diagnosing why my same setup seems to have a knocking sound. It only ever happens in 1st gear and only when I have just pulled away with a reasonable amount of throttle (no sound if I pull away lightly from rest)

I thought it might have been the rear CV joint as the 335i centre bearing, although aligning the shaft to the gearbox, has the effect of raising it a little in respect to the diff and therefore relying on that final cv joint.

[N111CUK]

Yep messed that up

New link http://www.e90post.com/forums/showth...9#post13781329

[phil200tdi]

I'm now considering this conversion..

Is there a way to use 335i Shocks/Springs with the M3 subframe? I recently fitted Eibach Pro/Bilstein B4s and hence don't wanna swap em all out again!

Same for the brakes - possible to reuse the 335i brakes?

How much did the work to the prop cost? How long would a competent mech take to fit?

[idnan]

Originally Posted by phil200tdi

I'm now considering this conversion..

Is there a way to use 335i Shocks/Springs with the M3 subframe? I recently fitted Eibach Pro/Bilstein B4s and hence don't wanna swap em all out again!

Same for the brakes - possible to reuse the 335i brakes?

How much did the work to the prop cost? How long would a competent mech take to fit?

Phil it is possible to reuse the brakes/hubs/shock mounts and that way I would recommend using your 335i subframe and arms but m3 diff and driveshafts. However the more hybrid you go the more problems you can run into with compatibility. Oh and use the m3 ARB and upgrade the front as well. I'm running e92 m3 rear and e93 m3 front (slightly thicker) which I like the feeling of.

I measured up the prop myself and paid under £100 to get the prop shortened, balanced and the joint rebuilt which was a good price. I can recommend the guy in Wolverhampton who did mine.

There may be teething problems to overcome as it is all custom and whilst it seems pretty straightforward, the labour hours can rack up.

[phil200tdi]

I would be doing this mainly to get the subframe and arms. My bushes are pretty shot and I don't fancy the labour to replace them when I can get an LSD for free with the upgrade!

The axle I'm looking at comes with shocks, are these compatible with 335i Eibach springs? Do you then need to upgrade the front to m3 brakes and shocks?

[N111CUK]

You'll need the shocks as the wishbones are different

[driver264]

HI ADAM SPOKE TO YOU ON PHONE
HAVE DONE SAME CONVERSION ON MY 135 DCT WITH M3 SUB FRAME CUSTOM PROP AND M3 SUB FRAME AND 315 DIFF ,BUT WHEN TAKING UP TO DRIVE CAR GEARBOX COG COMES UP WHEN CHANGING GEAR AND FEELS LIKE HOLDING BACK NOT SURE WHATS GOING ON COULD IT BE THE GEARBOX DCT IS READING THE RATIOS 256 FROM ORIGINAL SET BUT NOW 315 DIFF CAUSING PROBLEMS? ANY IDEA S HELP ANY ONE ? MARK