Fitting the E46 M3 6-speed gearbox to a US-model E36 M3

BACKGROUND



Starting in 1996, BMW fitted a 6-speed gearbox to the E36 M3 Evolution, the standard version of the M3 sold in all markets except the USA.  The American market cars were always unique to the US, de-contented and mechanically different in order to keep a lower price.  Principally, the US-market car differed from the Euro version in the motor (Euro 321bhp, multi throttle S50B32 engine, US 240hp, single throttle S52 engine) and in the absence of one gear.

The 6th gear in the Evolution M3 was simply an overdrive, the first five gears were the same ratios.  It could be said that the between the Autobahn and Autostrada, higher average cruising speeds made the overdrive a luxury that could be trimmed from the cars sold in the USA with our slower Interstate highways.

WHY MORE GEARS?

But having an overdrive is not the only reason to add more gears; by adjusting the final drive gearing, one can achieve the effect of a close-ratio gearbox and also have greater torque multiplication without a sacrifice in top-gear cruising... and even retain a taller top gear, getting "the best of both worlds" with deeper gearing and lower rpm at highway cruising speed.

Let's examine what changing the ratios does:

SPEED IN GEARS
'96+ E36 M3 final drive gearing remains the same in the 5-speed or 6-speed, same ratios in both gearboxes 1st-5th.
3.23 is the standard ratio in '96+ M3 whether fitted with 5-speed or 6-speed.

As we can see in comparison to the 5-speed gearing, both the 3.46 and 3.64 final drive change works out nicely for increasing torque multiplication while still maintaining 6th gear as an overdrive taller than the original 5-speed/3.23 combination.  BMW apparently felt the lower final drive gearing to be of a worthwhile benefit in the E46 M3, which shares the same transmission ratios and tire diameter (tire diameter affects complete overall gearing).  The early E46 M3 was fitted with the 3.64, later ones changed to an effectively indistinguishable 3.62.

THE TRANSPLANT CONCEPT

Installing the Evolution M3 6-speed gearbox into a US 5-speed M3 is a direct parts swap; transmission, shifter assembly, driveshaft, and a differential flange change are all that are needed.  What prevents more US E36 M3 owners from installing the 6-speed gearbox?  Cost is a factor; figure approximately $7000 in parts brand-new from BMW.  Used parts are definitely a viable option at a lower cost, but parts must be imported from overseas which can be considered a difficult and more expensive proposition, not to mention little resource should the parts prove to be defective.

However, with the US-market E46 M3 available now for around five years, many dismantled examples are available for parts-picking right here in the USA.  The cost of a used E46 M3 gearbox is certainly reasonable and the possibility of finding one locally (with a warranty) is attractive to American enthusiasts.

The E46 M3 6-speed gearbox is literally a "bolt in" for the E36 as the engine mounting points are shared, both the E36 S52 motor (and all other previous M50 iterations) and the E46 M3 S54 are identical in that respect.  With the exception of the driveshaft, all other conversion parts are available directly from BMW and/or quality aftermarket sources such as UUC Motorwerks.

PARTS REQUIRED:

PART	DESCRIPTION AND NOTES	AFTERMARKET ALTERNATIVE
	E46 M3 gearbox
	E46 M3 flywheel and sub-parts E46 flywheel must be used for E46 clutch.		UUC Stage2 flywheel with M5 hybrid clutch conversion results in acceleration gains, quicker rev-matching, and the use of a more durable clutch. Stage2 kit includes correct clutch.
	E46 M3 clutch and release bearing  must be used because E46 M3 input shaft uses a larger spline size than E36. Use original E36 clutch fork, retaining clip, ball pin.		UUC Direct-Fit clutch for the E46 M3 flywheel eliminates the Self-Adjusting Clutch (SAC) mechanism, resulting in better pedal feel, greater reliability. Basic clutch design has higher torque capacity and optional cerametallic versions for high-torque and drag-racing are available.
	E46 slave is not compatible with E36 slave line. E36 325i slave cylinder is correctly sized for the E46 M3 clutch and will maintain correct pedal effort.		UUC Stainless Steel clutch line (order part for E36 M3) will improve clutch pedal feel and is resistant to temperature changes which can change clutch engagement point.
	E36 M3 Evolution transmission support and new hardware. Can re-use original transmission mount bushings.		UUC Transmission Mount Enforcer setup consists of uprated bushings with enforcer cups to limit shear and rotational displacement of powertrain relative to shifter, improving shift accuracy.
	E36 M3 Evolution shifter, shifter carrier, selector rod, and associated hardware are a direct and perfect fit.		UUC Evolution3 Ultimate Short Shifter is the legendary benchmark in BMW shifter precision and smoothness. Kit for the E36 M3 6-speed includes every part required except selector rod (#9 in diagram to left).
	Any E46 or E36 6-speed knob can be used, part number diagram shows correct options for E36.		UUC RK6A-L is a leather- wrapped and height-adjustable work of art.  Extra mass of stainless steel makes for smoother shifts.
	Install new E36 flex disk and related parts.
	Zionsville Autosport offers the perfect custom-made driveshaft for this conversion. Originally offered as part of their 330i 6-speed conversion, it measures at the correct length for use with the M3 6-speed transmission. Note that the E36 M3 Evolution driveshaft can be used, but is not exactly the right length... the sliding section accomodates the difference, but technically the Zionsville Autosport driveshaft is a better choice and is comparably priced. Determine if you have a 4-bolt or 6-bolt flange on the differential  before ordering.
	KMS offers custom-built differentials with your choice of gear ratios and limited slip lockup.  Contact KMS at 440-564-7574 to discuss your needs.
(c) 2005 UUC Motorwerks