6-Speed Manual Conversion for S85

We’ve all been there. You’re ready to take off at the red light, you lift your foot off the brake, press the gas—and then… nothing. "DING"

A red cog! THE red cog of death for these cars. Almost as bad as having your rod bearings let go mid-pull on a spirited drive.

Don’t get me wrong—there’s absolutely no issue with the 7-speed automatic in terms of driving experience and gear-snapping excitement. The SMG 3 (Sequential Manual Gearbox) was a major part of the M5’s initial launch in 2005, and even today, it still holds its place inside these engineering marvels.

But the downside? Reliability issues start creeping in when these cars move into their second or third ownership. Rebuilding internals, rewiring harnesses, and replacing worn components become inevitable if you're chasing long-term durability.

While BMW’s goal was to deliver the best of both worlds—manual-like performance with automated control—the long-term viability of SMG 3 hasn’t aged as gracefully. Especially not for owners who push their S85s hard or plan to keep them for the long haul.

BMW revolutionized the driving experience by pushing the boundaries of automated shifting, offering an exhilarating drive with the SMG 3. However, as time went on, reliability concerns began to surface, making it clear that there were trade-offs. So, what can you do if your SMG 3 is starting to show its age?

Rebuilding the SMG 3: A Viable Option

The 6-Speed Manual Conversion: A Light at the End of the Tunnel

Alternatively, there is a light at the end of the tunnel—a true escape from the complexities and potential headaches of an SMG rebuild. Imagine yourself fully in control of your German V10 sedan, rowing through the gears with that raw, mechanical connection between you and the engine. This is the ultimate driving experience.

And while the SMG 3 may have been groundbreaking in its time, for many drivers, the pure joy of a 6-speed manual is unmatched. This is where we come in. We specialize in both repairing the SMG 3 and converting your car to a 6-speed manual—giving you the flexibility to choose the option that best suits your driving desires.

For those who prefer to rebuild their SMG 3, we provide expert services that adhere strictly to BMW’s factory standards, ensuring your transmission is as reliable as the day it was first installed. But if the manual experience calls to you, we can also help convert your car to a full 6-speed manual transmission, delivering that classic, tactile driving experience that only a manual can offer.

Our priority is the long-term performance of your vehicle. Whether you choose to repair or convert, we ensure that every step is completed with the same precision and care that BMW put into these machines when they first rolled off the production line.

The 6-Speed Manual Conversion: Your Journey Starts Now

Our journey to convert the M5 E60 from an automated manual transmission (SMG) to a fully functional 6-speed manual transmission starts now. When these cars were first sold, BMW gave first owners the rare option to spec their M5 or M6 with a stick. Allegedly, only about 1 in 10 owners took that path.

While most cars came equipped with the SMG system, every E60, E61, E63, and E64 chassis was designed to accommodate the 6-speed manual. The transmission used for this swap is the GS6-53BZ-TJGC, originally found in the manual S65-powered M3 models (E90 and E92).

This transmission is almost identical to the one that came in the M5 and M6—the GS6-53BZ-THGR—but minor adjustments are required to ensure proper fit and function with the S85 engine.

While the THGR transmission housing is the same and shares the same mounting bolt pattern, there are key differences in transmission mounts, bell housing fitment, clutch, slave cylinder, and removal of the transmission oil cooler.

The 6-Speed Manual Swap: S85 Side

The process begins by carefully removing the existing transmission and related components to make room for the new setup. This involves disconnecting and removing the exhaust system, driveshaft, flywheel, and the Transmission Control Unit (TCU).

With the car disassembled, we use this opportunity to perform critical preventive maintenance. If the following components are still original, this is the best time to replace them to avoid future failures:

• Crankcase Breather Hose – 11617838897 (Left Line) – Qty: 1
• Crankcase Breather Hose – 11617838898 (Right Line) – Qty: 1
• Crankcase Vent Valve – 11617836553 – Qty: 2
• Rear Main Seal – 11217838071 – Qty: 1
• Exhaust Gaskets & Bushings – (Inspected on removal) – Qty: As needed

A key area is the rear subframe bushings. These wear over time and can crack—especially problematic when converting to a manual transmission. Hard launches with worn bushings can damage the subframe’s differential mounting tabs.

BMW has since updated these bushings with improved versions. Replacing them and reinforcing the subframe is recommended if wear or damage is present.

For more on reinforcement and servicing the driveline, visit our BMW Service: Rear Drive Train Service for S85 page: [link coming soon].

Clutch Control

Pedal Assembly

Other Parts

Shift Knob & Accessories

The 6-Speed Manual Swap: Transmission Side

If a Brand New GS6-53BZ-THGR or GS6-53BZ-TJGC Gearbox Assembly hasn’t been sourced, but a Used one has, it’s critical to inspect its condition before installation. We recommend a gearbox housing rebuild. Although not required, this includes inspection of key components such as the guide sleeve, shaft seals, and breather tube.

These parts are far easier to replace with the transmission out of the car, ensuring a fully sealed housing and preventing potential issues once everything is reassembled. Components like the backup light switch, cover lid, and torx screws are also checked and replaced if necessary, along with servicing the oil.

GS6-53BZ-THGR

• Manual M5/M6 E6X 6-Speed Gearbox Assembly – 23002283151 – Qty: 1
• Mechanical: Directly matches M5/M6 E6X S85 setup
• Electrical: Includes M5/M6 E6X Transmission Harness – 23017840637
  Replacement not required

GS6-53BZ-TJGC

• Manual M3 E9X 6-Speed Gearbox Assembly – 23002283601 – Qty: 1
• Mechanical: Requires plugging external oil cooler ports
• BimmerPro Custom Cooler Plug – Part Number: N/A
  Visit product page: [Link coming soon]
• Electrical: Includes Manual M3 E9X Harness – N/A
  Or use M5/M6 E6X Harness – 23017840637
  *Required – M3 harness can be adapted for S85

Conversion & Optional Rebuild Parts

• Clutch Kit – S85 Compatible – 21212284048 – Qty: 1
• Flywheel – Lightweight or OEM – 21212282996 – Qty: 1
• Clutch Slave Cylinder with Line – 21526785966 – Qty: 1
• Shift Linkage & Carrier Assembly – 25117529033 – Qty: 1
• Clutch Pedal & Master Cylinder Kit – 35006861340 – Qty: 1

Optional Gearbox Rebuild Items (Recommended for Used Units):

• Input Shaft Guide Sleeve – Qty: 1
• Shaft Seals (Input & Output) – Qty: 2
• Breather Tube – Qty: 1
• Backup Light Switch – Qty: 1
• Cover Lid & Torx Fasteners – Qty: Various
• Gearbox Oil (MTF-LT) – Qty: 2L

These items ensure your transmission is fully refreshed and sealed for long-term reliability, especially if you’re working with a previously used gearbox.

Shifter Carrier

Clutch Components

Gearbox Mounting

Gearbox Housing (Not Required)

The 6-Speed Manual Swap: Interior Modifications (Not Required)

When converting your BMW M5 or M6 from the SMG transmission to a 6-speed manual, it’s not just about swapping the gearbox. The interior requires modifications to properly accommodate the new shifter. While not mechanically required, these updates ensure the cabin retains a clean, OEM appearance and functional layout.

Center Console Trim

One of the most noticeable visual changes is the Center Console Trim. The SMG-specific trim must be replaced to fit the manual shifter. Whether you opt for aluminum or wood finish, the new trim must accommodate a standard manual layout.

Along with the trim, the Oddments Tray is also updated. Originally equipped with a retractable cover exposing only the ashtray and lighter outlet, the manual version replaces this with a fixed plastic tray. The new tray retains the lighter outlet and includes a proper holder for the EDC Button, but removes the ashtray entirely.

• PRE-LCI Manual M5/M6 E6X Center Console Trim – 51168037228 – Qty: 1
  Includes: Oddments Tray – 51168037213 – Qty: 1

If you choose the LCI Manual Setup discussed later, the ashtray is relocated to a drawer beneath the radio. This requires a different Oddments Tray without the lighter outlet, since that outlet will now be integrated into the relocated drawer. This change affects both layout and appearance of your center console, so plan accordingly.

• LCI Manual M5/M6 E6X Center Console Trim – 51167903537 – Qty: 1
  Includes: Different Oddments Tray – 51168045434 – Qty: 1

The EDC Button is reused from the SMG 3 Shifter Surround. No replacement required unless damaged.

• M5/M6 E6X EDC Button – 61317834518 – Qty: 1
  Reuse from existing trim

SZM Switch Module

A crucial part of the manual conversion involves updating the SZM (SteuerZentrale Modul) switch setup. The SZM controls multiple interior functions, including seat heating, ventilation, and driving modes like MDM (M Dynamic Mode) and DTC (Dynamic Traction Control). During the conversion, we’ll relocate the MDM/DTC button from the original SMG 3 Shifter Surround Trim to the new SZM switch setup, ensuring that these controls remain easily accessible and functional.

The SZM is also responsible for managing seat functions, so we must source the right module based on your car’s specific configuration. All M5 and M6 models come with at least a driver’s heated seat as standard, and some also feature ventilated seats. If your car has them, we’ll ensure the new SZM supports this function. For vehicles with only heated seats, we’ll opt for an SZM without ventilation controls.

Additionally, all M5 models come equipped with cornering bolsters as part of the seat setup. We’ll source the appropriate SZM from a Manual M variant to ensure full compatibility with this feature, which is essential for proper seat function.

By sourcing and installing the correct SZM, we’ll make sure that all seat functions, including MDM/DTC button relocation, remain intact and reliable.

As many of the components for this swap are no longer in production, sourcing parts from a Manual S85 (used market) can be crucial for achieving the right look. Finding the right buttons, switches, and connectors ensures a factory-like finish while making sure your M5 or M6 operates exactly as BMW intended.

• PRE-LCI Manual M5/M6 E6X SZM Switch Module – N/A – Qty: 1

LCI Manual Setup

LCI (Life Cycle Impulse) was BMW’s term for the mid-life facelift of a model, typically around the midpoint of its production run. For the E6X M5 and M6, this update came in 2008 and included enhancements like updated headlights and interior electronics.

When converting to a manual transmission, we often pivot to LCI components because sourcing pre-LCI parts has become significantly more difficult. In contrast, LCI components such as the ECU Switch, 32-pin connector (X16919), and both Left (X17257) and Right (X17259) Switch Block Buttons are more readily available.

However, transitioning to LCI parts isn’t plug-and-play—it requires rewiring and replacing related components such as the CCC (Car Communication Computer) with the CIC (Car Information Computer), along with the menu controller and wiring.

The MDM/DTC button functionality must also be relocated as part of this process. If you're already LCI, only the left switch block button needs to be changed.

• LCI M5/M6 E6X ECU Switch (Electronic Control Unit) – 61319183228 – Does not include required connector: X16919 (32 PIN) – *Replacement not required if already LCI – Qty: 1

LCI Manual M5/M6 E6X Switch Block Buttons S839 (Left)

• Active backrest with adjustment: NO, Climate-controlled seats: NO – 61319159062
• Active backrest with adjustment: NO, Climate-controlled seats: YES – 61319159063
• Active backrest with adjustment: YES, Climate-controlled seats: NO – 61319159064
• Active backrest with adjustment: YES, Climate-controlled seats: YES – 61319159065
• Connector: X17257 (3 PIN) not included – *Connector replacement not required if already LCI – Qty: 1

LCI Manual M5/M6 E6X Switch Block Buttons S840 (Right)

• Seat heating: NO, Backrest: NO, Active seat: NO, Climate: NO, PDC: NO – 61319159067
• Seat heating: NO, Backrest: NO, Active seat: NO, Climate: NO, PDC: YES – 61319159076
• Seat heating: NO, Backrest: YES, Active seat: NO, Climate: NO, PDC: NO – 61319159073
• Seat heating: NO, Backrest: NO, Active seat: YES, Climate: NO, PDC: NO – 61319159070
• Seat heating: NO, Backrest: YES, Active seat: NO, Climate: NO, PDC: YES – 61319159082
• Seat heating: YES, Backrest: NO, Active seat: NO, Climate: NO, PDC: YES – 61319159077
• Seat heating: NO, Backrest: YES, Active seat: NO, Climate: NO, PDC: YES – 61319159079
• Seat heating: YES, Backrest: NO, Active seat: YES, Climate: NO, PDC: NO – 61319159071
• Seat heating: YES, Backrest: YES, Active seat: NO, Climate: NO, PDC: NO – 61319159074
• Seat heating: YES, Backrest: NO, Active seat: NO, Climate: YES, PDC: NO – 61319159069
• Seat heating: YES, Backrest: NO, Active seat: YES, Climate: NO, PDC: YES – 61319159083
• Seat heating: YES, Backrest: YES, Active seat: NO, Climate: NO, PDC: YES – 61319159080
• Seat heating: YES, Backrest: NO, Active seat: NO, Climate: YES, PDC: YES – 61319159078
• Seat heating: YES, Backrest: NO, Active seat: YES, Climate: YES, PDC: NO – 61319159072
• Seat heating: YES, Backrest: YES, Active seat: NO, Climate: YES, PDC: NO – 61319159075
• Seat heating: YES, Backrest: YES, Active seat: NO, Climate: YES, PDC: YES – 61319159084
• Seat heating: YES, Backrest: NO, Active seat: YES, Climate: YES, PDC: YES – 61319159081
• Connector: X17259 (3 PIN) not included – *Replacement not required if already LCI – Qty: 1

For more details on the LCI conversion process, including the change from CCC to CIC, Menu Controller, Custom Wiring and other components, please refer to our BMW Service: Center Console LCI Retrofit for S85 page [click here].

Steering Wheel

As part of the manual transmission conversion, the steering wheel requires an upgrade to complete the aesthetic look. The shift paddles, originally mounted to the SMG steering wheel, become obsolete, as they no longer serve any purpose. If removed, they leave holes in the back of the wheel. While replacing the steering wheel isn’t strictly necessary for the conversion to function, it cosmetically completes the manual swap.

BMW offered two steering wheel options for manual M vehicles: one with heating capability and one without. Both options are listed below:

• 1. Manual M5/M6 E6X Steering Wheel (Non-Heated) — 32342283933 – Qty: 1
• 2. Manual M5/M6 E6X Steering Wheel (Heated) — 32342283937 – Qty: 1

If your current steering wheel lacks heating but you would like to add this feature, the retrofit involves more than just the wheel replacement. In addition to the new steering wheel, a new Switch Unit Steering Column, Coil Spring Cartridge, Steering Wheel Control Button, and Custom Wiring are required. We can assist with this retrofit to integrate the heated steering wheel seamlessly into your M5 or M6.

For more details, visit our BMW Service: Heated Steering Retrofit for S85 page: [Link coming soon].

Completed

At this stage of the manual conversion, the manual transmission and essential functions are fully operational.