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 – ••••••••••• OE Part Number
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• Crankcase Breather Hose – ••••••••••• OE Part Number
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• Crankcase Vent Valve – ••••••••••• OE Part Number
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• Rear Main Seal – ••••••••••• OE Part Number
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• 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, it’s critical to inspect its condition before installation. We recommend a gearbox housing rebuild. Although *Not Required this involves inspecting key components, such as the guide sleeve, shaft seals, and breather tube. These parts are much easier to replace with the transmission out of the car, ensuring the housing is fully sealed and free of any potential issues that could arise once everything is back together. Components like the backup light switch, cover lid, and some torx screws are also checked and replaced if necessary along with servicing the oil.

These parts are far easier to replace with the transmission out of the car.

GS6-53BZ-THGR

• GS6-53BZ-THGR – Manual M5/M6 E6X 6-Speed Gearbox Assembly – ••••••••••• OE Part Number
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• Mechanical: Directly matches M5/M6 E6X S85 setup
• Electrical: Includes M5/M6 E6X Manual Transmission Harness – ••••••••••• OE Part Number
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  Replacement not required

GS6-53BZ-TJGC

• GS6-53BZ-TJGC – Manual M3 E9X 6-Speed Gearbox Assembly – ••••••••••• OE Part Number
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• Mechanical: Requires plugging external oil cooler ports
• BimmerPro Custom Cooler Plug – Part Number: N/A
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• Electrical: Includes Manual M3 E9X Manual Transmission Harness – ••••••••••• OE Part Number
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• Or use M5/M6 E6X Manual Transmission Harness – ••••••••••• OE Part Number
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  *Required – M3 E9X Manual Transmission Harness needs to be adapted for the S85

Clutch & Flywheel Options + Required Conversion Parts

• OEM M5/M6 E6X Manual Stock Setup – Balanced, OEM-based configuration
  • Flywheel – ••••••••••• OE Part Number
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  • Clutch Kit – ••••••••••• OE Part Number
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• Preferred "Lightweight" M3 E9X Manual Setup – More aggressive, performance-oriented configuration
  • Flywheel – ••••••••••• OE Part Number
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  • Clutch Kit – ••••••••••• OE Part Number
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• Clutch Slave Cylinder with Line
• Shift Linkage & Carrier Assembly
• Clutch Pedal & Master Cylinder Kit

Optional Gearbox Rebuild Items (Recommended for Used Gearbox Assembly):

• 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

Here’s the list of the gearbox parts required for the mechanical conversion, as well as the *Not Required gearbox housing rebuild parts to service a Used GS6-53BZ-THGR or GS6-53BZ-TJGC Gearbox Assembly.

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 out the gearbox. The interior also requires modifications to accommodate the new shifter and related components. Although not mechanically required This process ensures that the car maintains its functional features with an OEM look.

Center Console Trim

One of the most noticeable changes during the manual conversion is the Center Console Trim. The original trim, designed for the SMG setup, must be replaced to accommodate the manual shifter. Whether aluminum or wood.

Along with the new center console trim, the Oddments Tray below the console is also updated. Originally, this tray featured a retractable cover that exposed only the ashtray and lighter outlet, with no other buttons inside. With the manual setup, the retractable cover is replaced by a new, fixed plastic storage tray. This new tray retains the lighter outlet and now features a holder for the EDC Button. This change removes the only ashtray from the front center console.

• PRE-LCI Manual M5 E6X Center Console Trim – ••••••••••• OE Part Number
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  Includes Oddments Tray – ••••••••••• OE Part Number
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  Includes EDC Button – ••••••••••• OE Part Number
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• PRE-LCI Manual M5 E6X Oddments Tray – ••••••••••• OE Part Number
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  Includes EDC Button – ••••••••••• OE Part Number
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  Currently backordered

Alternatively, if you choose the LCI Manual Setup option discussed later, the ashtray is relocated to a new drawer beneath the radio. In this case, a Different Oddments Tray without the lighter outlet is required, as the outlet will now be present in the newly located drawer. It’s important to keep this in mind when planning your conversion, as this choice affects both the functional layout and the overall appearance of the center console.

• LCI Manual M5 E6X Center Console Trim – ••••••••••• OE Part Number
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  Includes Oddments Tray – ••••••••••• OE Part Number
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  Includes EDC Button – ••••••••••• OE Part Number
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  Currently backordered
  
  LCI Manual M5 E6X Oddments Tray – ••••••••••• OE Part Number
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  Includes EDC Button – ••••••••••• OE Part Number
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  Currently backordered

Additional Components Required for LCI Conversion

For LCI conversions, the updated iDrive controller requires specific mounting components to fit properly. Below are the required parts:

• LCI iDrive Telematics Input Controller – ••••••••••• OE Part Number
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  Includes Trim Ring – ••••••••••• OE Part Number
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• iDrive Controller Mount Frame – ••••••••••• OE Part Number
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• iDrive Controller Support – ••••••••••• OE Part Number
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• Controller Trim Ring (Pearl Grey) – ••••••••••• OE Part Number
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  Can be replaced if a used controller is sourced with a damaged ring

Replacement not required, use the EDC Button from the SMG 3 Shifter Surround Trim

• M5/M6 E6X Switch EDC Button – ••••••••••• OE Part Number
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  Reuse from existing trim

Steering Wheel

As part of the manual transmission conversion...

BMW offered two steering wheel options for manual M vehicles...

• 1. Manual M5/M6 E6X Steering Wheel (Non-Heated) — ••••••••••• OE Part Number
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• 2. Manual M5/M6 E6X Steering Wheel (Heated) — ••••••••••• OE Part Number
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If your current steering wheel lacks heating but you would like to add this feature...

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.