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Miata to BMW E46 6-speed transmission upgrade is available for order!

David Calzada

We’ve completed our BMW E46 6-speed transmission testing and are now ready to take orders of these long-awaited kits. Our transmission kits are 100% proudly made in the USA. Anticipated lead time to ship orders is less than 30 days.

We now have a parts package that bolts an E46 6-speed transmission into the NA and NB Miata chassis. Adapter plates and flywheels are available to work with both the Mazda BP and Honda K series engines. These same adapters and flywheels will be available separately for those completing one-off projects.

The initial production run is just 10 kits. Once these are sold out, we will have more in stock in another 30 days.

Final product photos are in the works now and will be on the site soon.

 

Compatible Transmissions

The ZF 6-speed transmission used for the kit is the GS6-37BZ, found in the following vehicles:

-E46 chassis, 2003.5-2006 330i and 330Ci 6-speed cars. (Note the these cars were also available with the ZF 5-speed transmission, as well as an SMG 6-speed. Neither of those are compatible with this 6-speed kit)

-E60/E61 chassis, 2002-2005 BMW 530i 6-speed cars

 

 

Why this transmission?

It's a compact 6-speed gearbox with comparable gearing to the Miata 6-speed, but MUCH stronger. These transmissions have been known to handle 800+whp in BMW applications. They fit inside a Miata without any transmission tunnel modifications, and they are also readily available used for reasonable prices. Check out our gear ratio calculator to configure the best transmission and differential combo for your setup.

Please note: The Getrag 420G transmission found in the E46 M3 is not compatible with this kit. The rear of this transmission is not able to be easily mounted in the Miata tunnel and so our mounts and flywheel are design specifically for the ZF 6-speed.

This transmission also allows us to use the inexpensive OEM replacement E46 6-speed clutch kit that pairs with our custom flywheel. The pressure plate on this clutch is also found on the E46 M3 and E39 M5, so it’s up to the task to handle turbo 4 cylinder torque in many applications. Note that the ZF 6-speed uses a 22 spline clutch disc, unlike the ZF 5-speed that uses a 10 spine disc. So a clutch disc specific to this transmission is a requirement.

 

Parts Packages and Pricing

Our transmission kit provides everything needed for a bolt-in transmission upgrade. The shifter action is quite good: crisp and precise, and mimics the Miata shifter geometry perfectly. There is a minor increase in NVH when installing this kit thanks to the firm transmission mount, but nothing overwhelming. The upgraded components will be welcome for our high horsepower customers.

Unlike our ZF 5-speed kit that includes a transmission mount that bolts inside the tunnel, the ZF 6-speed kit includes a set of V8R frame rails, a rear crossmember, and a rear transmission bracket that accepts a poly GM style rear transmission mount (very similar to the T56 style mounts on the market).

 

 

BP or K to ZF 6-Speed Transmission Package: $2995.00

This package includes the following parts:

-Engine/transmission adapter plate, for either Mazda BP or K series engine CNC machined steel, zinc plated, with all hardware and dowel pins.

-A specific BP or K (+$100) to E46 6-speed flywheel (different geometry than the 5-speed). This flywheel  (12 lb.) bolts directly to the BP or K crank and accepts a 240mm E46 clutch kit, 22 spline.

-Short shifter, stainless steel, with Miata geometry on top (Miata 10x1.25 thread pitch, height, shape, and throw are identical). The shifter has ZF 6-speed specific BMW geometry on the bottom. Ball bearings replace the OEM BMW plastic components for improved shifter action.

-Custom length selector rod, stainless steel, dual sheer design. Our design eliminates all components that often result in a sloppy BMW shifter.

-Custom selector joint (no more worn plastic bushings) and stainless steel shifter pins, with retainer clips.

-6-speed shifter plate, billet aluminum, that bolts to the top of the Miata transmission tunnel and replaces the rubber Miata outer boot. It accepts the BMW shifter ball bushing and our custom short shifter in the center.

-Steel 500+hp rated driveshaft. Can be configured to bolt to a GM Getrag diff or a solid-mounted Miata Torsen diff.

-V8R frame rails with transmission crossmember pads, powdercoated black

-ZF 6-speed transmission crossmember

-ZF 6-speed rear transmission mount bracket

-Energy Suspension GM style poly transmission mount

-¾” Wilwood clutch master cylinder kit with braided stainless clutch line

-E36 clutch slave cylinder

-BMW reverse light connector with pigtails

-Installation instructions

-Optional Delrin or Stainless Steel shift knob with KMiata logo and BMW 6-speed shift pattern. Standard M10x1.25 Miata thread pitch.



 

K to ZF 5 Speed Package: $3095.00

Existing customers with K series swaps can use this package to upgrade to the BMW transmission setup. This kit includes all of the same components as the BP kit listed above, but with a K series to ZF-6 flywheel and our K to E36/E46 adapter plate.

Unlike the K to ZF 5-speed setup, a custom release bearing is not needed.


KMiata Conversion Kit with ZF 6-Speed Transmission Components: $5795.00

Note that this is not our popular K24 Ultimate swap package, but our original K series swap kit (no header, intake manifold, etc). This kit is a platform for customers to build their own custom setups. This is the ideal starting point for high horsepower boosted applications. Pair this kit with big intake manifolds, custom turbo setups, and turn up the boost. For best results, add a Getrag differential swap too. All details can be found here.


Speedometer Wiring

We initially set up our test car with a GPS-based speedometer adapter, but were disappointed with the slow refresh rate on track. We are now using a Dakota Digital universal speedometer interface kit ($80 from Summit Racing, part #SGI-5E) paired with a single ABS wheel speed sensor on one hub. This works well for NB cars with the electric speedometer, and we are putting together a solution for NA cars now to accommodate the older cable-driven speedometers. More details coming soon.


Shift Knobs

We designed our shifters to accept any Miata shift knob (M10x1.25 thread pitch). However, since the reverse gear location is different on the BMW transmission, custom shift knobs were in order.

KMiata shift knobs come in black Delrin or stainless steel, with options for the BMW 5 and 6 speed shift patterns as well as Miata 5 and 6 speed shift patterns for the rest of the Miata community.


Fluid

BMW calls for automatic transmission fluid (ATF) for the GS6-37BZ transmission, as well as most other BMW manual transmissions. Redline D4 ATF is very common among BMW racers, and we’ve been pleased with it in our test car.

 

Miata Differential Mount for Easy PPF Delete!

If you're choosing to retain the Miata diff with this transmission upgrade, we're very close to releasing our Miata differential mount that makes deleting the power plant frame (PPF) very easy. Details and pictures are coming soon!

Questions? Email us at sales@kmiata.com. Ready to order? Click here to reserve your package today.