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Description
diff gear ratio BMW M Gear Ratio Swap Set | M3, M5, M6, Z4M Differential UpgradeBMW M Gear Ratio Swap Set Complete Installation Kit Enhance the performance and driving experience of your BMW M3, M5, M6, and Z4 M with the RacingDiffs Gear Ratio Swap Set. The kit includes all essential components to change your differentials gear ratio with factory level precision and reliability. Key Features Complete kit: All parts required for a precise, repeatable gear ratio swapno guesswork. Performance gains: Tailor acceleration and
BMW M Gear Ratio Swap Set — Complete Installation Kit
Enhance the performance and driving experience of your BMW M3, M5, M6, and Z4 M with the RacingDiffs Gear Ratio Swap Set. The kit includes all essential components to change your differential’s gear ratio with factory-level precision and reliability.
Key Features
- Complete kit: All parts required for a precise, repeatable gear-ratio swap—no guesswork.
- Performance gains: Tailor acceleration and drivability to your use case (street, track, time attack).
- OEM-level precision: Components manufactured to meet or exceed OEM specifications.
- Guided install: Step-by-step tutorial + video walkthrough linked below.
What’s in the Box
- Adjustment Shim Set — aligns and positions internal components correctly.
- Pinion Oil Seal — prevents leaks and maintains optimal lubrication.
- Large Pinion Bearing — required to install onto the new pinion from your new gear set.
- Crush Sleeve Shim — sets the correct pinion bearing preload.
- Pinion Position Shim Set (2.5–3.5 mm) — precise pinion depth adjustment.
Performance Benefits
- Stronger acceleration with the right final drive for your build and tracks.
- Optimized top-end and gear spacing for your engine’s power band.
- Long-term reliability when backlash and preload are set correctly.
- Expert support from RacingDiffs if you need guidance selecting shims or ratios.
Technical Specs / Installation Tips
| Use case | Gear ratio change on BMW M differentials (see fitment variants below). |
| Pinion setup | Set pinion depth using the Pinion Position Shim Set (2.5–3.5 mm) and establish correct preload with the Crush Sleeve Shim. |
| Backlash | Adjust with the Adjustment Shim Set until backlash is within spec; verify gear contact pattern with marking compound. |
| Sealing | Install the new Pinion Oil Seal; lightly oil lips; ensure no nicks on yoke surface. |
| Torque notes | Clean threads; apply medium-strength threadlocker on ring-gear bolts; torque in a star pattern per BMW spec. |
| OEM references | Backlash adjustment shims: 33139065736 (33-13-9-065-736 / 33 13 9 065 736 / 33.13.9.065.736) 33139065737 (33-13-9-065-737 / 33 13 9 065 737 / 33.13.9.065.737) |
Tip: Always re-check preload/backlash after first heat cycle or track day.
Fitment (Variants)
Variant 1 (V1):
- E36 M3 (3.2 S52)
- E46 M3
- E28 M5, M535
- E34 M5
- E39 M5
- E24 M6
- E60 M5
- E63 / E64 M6
- Z4 M
Variant 2 (V2):
- E90 / E92 / E93 M3
If you’re unsure about compatibility, send us the last 7 digits of your VIN and we’ll confirm the right set for your car.
Shipping Notes
- Free Standard Shipping on $100+ Orders to the USA.
- Except Preorder products are shipped in 48 hours.
- Delivery to the USA:
- Standard Shipping : 3-10 business days
- If time is of the essence, please consider selecting expedited delivery for faster service.
Exchange/Return Notes
- We offer a 30-day return/exchange service after receiving.
- Final sale items are not eligible for returns or exchanges.
- To process your return/exchange, please contact us at [email protected]
- Please click here for more details>>> Return & Exchange Policy
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★★★★★ 5
Good shirt and value
Size: Large, Color: Blue
Coofandy is a good brand. I’ve ordered their products before. Good fit, good feel, and durable. Good value.
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Reviewed in the United States on August 25, 2025
★★★★★ 4
Great Color Dress shirt
Size: Medium, Color: Light Green
I purchased this dress shirt for my husband when he needed something to wear as a wedding guest. My dress had a bit of turquoise in it so we thought this would be a good compliment to what I was wearing. We ordered his normal dress shirt size and this was a perfect fit.My husband is slim and it was nice that this shirt wasn't boxy at all. The neck was a comfortable size and the arm length was spot on. He has nicer, more expensive dress shirts of better quality but this seemed to work out just fine for what we needed. The color was a nice shade of turquoise.. not too green and not too blue so we lucked out in that area also. We did wash this before wearing. My husband didn't complain about any stiffness/scratchiness etc.the whole day! I would say anyone wanting to purchase this shirt, that they will be pretty happy with the overall fit and comfort.
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Reviewed in the United States on July 25, 2024
★★★★★ 5
A dress shirt that allows for needed length.
Size: X-Large, Color: Light Green
Very nice dress shirt for a reasonable price, and for a size XL, the sleeves are actually long enough. The fit is relaxed and looked very professional, with a tie if one is appropriate.
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Reviewed in the United States on March 24, 2025
★★★★★ 5
Nice color
Size: XX-Large, Color: Pink
Exactly like the picture. Nice color
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Reviewed in the United States on April 29, 2026
★★★★★ 5
Nice shirt for the money
Size: X-Large, Color: Pink
Good comfortable fit
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Reviewed in the United States on June 1, 2026