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BMW Transmission Upgrade Packages For Miatas Available for Pre-Order

David Calzada

The time has finally come. We’ve completed our E36/E46 transmission testing and are thrilled to begin a pre-order of these long-awaited products. Our transmission upgrade components are 100% proudly made in the USA.

We’re kicking things off with the complete parts package needed to pair the popular ZF 5 speed BMW transmission to both the Mazda BP and Honda K series engines. All adapter parts are available for a complete bolt-in swap in the NA and NB Miata chassis, and we also have adapter plates and flywheels available separately for customers working on custom RWD K series projects.

Initial quantities are limited! Pre-order packages are linked at the bottom of this page. 

If you’re not familiar with our recent development on this product line, please read our original blog post here (note that certain details have changed since time of writing). Also be sure to check out our gear ratio calculator here as well.

After this initial release, parts for the E46 330i ZF 6 speed transmission will be available, as well as parts for the E30 Getrag 260 transmission. All of these components have already been designed and prototyped, but since we envision the ZF 5 speed to be the most common option among racers, we’re bringing it to market first. If you’re interested in either of these other two transmission options, be sure to sign up for our email newsletter so you’re notified of the release.

Anticipated lead time to ship all pre-orders is 30-45 days. As a special thank you, we're providing special introductory pricing and FREE SHIPPING on all pre-ordered items, as well as one of our beautiful new KMiata shift knobs for free with each transmission upgrade package.

Please excuse the lack of final product photos. These will be done and live before items actually start shipping.



Compatible Transmissions

The stout ZF 5 speed transmission (S5D-320Z) used for this kit can be found in the following BMW vehicles, and weighs only 77 lbs.:

E36 chassis, 1992-1998 3 series, 5 speed cars equipped with a 2.8L or larger engine (328i or M3)

E46 chassis, 1999-2006 3 series, 5 speed cars equipped with a 2.8L or larger (328i or 330i)

Z3 and Z4 chassis with 2.8L or larger engines

 

The smaller 5 speed transmission from the 323i and 325i are not quite as strong and have different shifter geometry, so we recommend going with the larger and stronger ZF 5 speed that has been the focus of our parts development.

This transmission also allows us to use the inexpensive OEM replacement E46 5 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.

Please note that our production adapter plates will be ground smooth and zinc-plated like our current K to Miata adapter plates.


Parts Packages and Pricing

Our transmission kit provides everything needed for a bolt-in transmission upgrade. Our custom short shifter action is quite good. It's crisp and precise, and mimics the Miata shifter geometry perfectly.

There is a minor increase in NVH when installing this kit thanks to the stiffer bushings and tunnel-mounted shifter, but nothing overwhelming. The upgraded components will be welcome for our high horsepower customers.

Holes need to be drilled in the side of the transmission tunnel to bolt the rear mount in place, but otherwise no tunnel modification is needed.


BP to ZF 5-Speed Transmission Package: $2595.00

This package includes the following parts:

-Mazda BP Engine/transmission adapter plate, CNC machined steel, zinc plated, with all hardware

-Flywheel that bolts to the BP engine and accepts an E46 clutch kit (13 lb, 6061 aluminum), with replaceable friction surface.

-Short shifter, stainless steel, with the upper portion retaining Miata geometry (10x1.25 thread pitch, height, shape, and throw are identical). The lower portion of the shifter has transmission-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.

-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.

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

-ZF 5 speed rear transmission mount, powdercoated steel, with all hardware (tunnel mounted)

-Upgraded rear transmission rubber or poly bushings, 3 hardness options available

-13/16” Wilwood clutch master cylinder kit with braided stainless clutch line

-E36 clutch slave cylinder, Sachs brand or equivalent

-BMW reverse light connector with pigtails

-Installation instructions

-Pre-order customers only: Free KMiata shift knob in black Delrin or stainless steel, with the proper BMW shifter pattern (reverse is to the left and up, instead of right and down).

-Optional OEM BMW E46 clutch kit (+$200)

-Optional V8 Roadsters Getrag diff upgrade (highly recommended for high horsepower applications and improved gear ratios). We will also have a rear Torsen mount coming to market soon to allow easy deletion of the PPF.

 

Here are some final production shots as well as pre-production adapter plates.

ZF 5 speed bolt-in short shifter kit for NA and NB chassis:

 Rear transmission mount with poly bushings pictured:

13/16" Wilwood master cylinder:

BP to E46 flywheel with an unfinished adapter:

Again, production adapter plates will be zinc-plated.

 

K to ZF 5 Speed Package: $2895.00

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, with the addition of a custom extended Tilton release bearing.

Due to the large spacing between the K series crank and the BMW release bearing, we designed an extended stainless steel release bearing (not pictured) which enabled us to remove a full inch of material off the flywheel face, making the K-E46 flywheel the lightest flywheel we offer. This custom bearing must be used in conjunction with the flywheel for proper clutch engagement.

 

KMiata Conversion Kit with ZF 5 Speed Transmission Components: $5695.00

Note that this is 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, and custom turbo or supercharger setups. For best results, add a Getrag differential swap too. 

This package swaps out the original K-Miata adapter plate and flywheel for the BMW components and adds in the rest of transmission package so you get the K to ZF 5 Speed Transmission Package shown above, plus:

-KMiata subframe and engine mounts

-KMiata aluminum baffled oil pan

-KMiata oil pump adapter and pickup tube

-KMiata wiring conversion harness

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, we decided that some custom shift knobs were in order.

In the next few weeks we will have custom KMiata shift knobs available (Delrin and stainless options) 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.

Pictures coming soon!


Transmission Service

BMW calls for automatic transmission fluid (ATF) for the S5D 320Z 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 two test cars. We now have this fluid in stock.

A known issue with this specific transmission is that the “detent pins” that are responsible for centering the shifter get worn out and stick. Symptoms include the shifter not returning back to center while in neutral, usually sticking towards 1st or 5th.

Thankfully, BMW has already revised the design of the shifter pins for this transmission, so we recommend replacing the pins before installing the transmission into the vehicle. The parts are inexpensive and can be purchased from many BMW parts suppliers as a kit.The transmission case does not need to be opened up to do this, everything can be accessed from the outside. 

Thayer Motorsports carries the replacement shift pins, and they also rent or sell the special service tools needed to do the job. We own a set of the tools and can’t imagine doing the job without them.

 

Ready to Order?

Click here to be directed to all options in our online store. You can add full packages as well as individual components to your cart and take advantage of the pre-order free shipping promotion. If you have questions before ordering, don't hesitate to call or email.