BMW GS6-37BZ 6-Speed Manual Transmission (RWD) · BMW / MINI · Expert rebuild service since 1987. Lifetime warranty. Free diagnostic.
2004–2011 BMW 3 Series (E90/E92 323i/325i/328i), 2009–2016 BMW Z4 (sDrive23i/sDrive30i), 2008–2013 BMW 1 Series (128i/135i early M57)
| Configuration | 6-speed manual RWD transmission |
|---|---|
| Gear Ratios | 1st 4.23:1 · 2nd 2.52:1 · 3rd 1.66:1 · 4th 1.22:1 · 5th 1.00:1 · 6th 0.84:1 · Rev 3.50:1 |
| Fluid Type | BMW MTF-LT-2 or MTF-LT-5 Manual Transmission Fluid |
| Fluid Capacity | 2.8 qts total, full drain-and-fill at service |
The GS6-37BZ 3rd and 4th synchros wear from high-revving enthusiast driving and neglected fluid. BMW 3 Series sport driving accelerates wear.
Symptoms: Crunching engagement in 3rd or 4th gear when cold or when shifting quickly, improved after warm-up
The reverse gear lockout mechanism wears or breaks, allowing accidental reverse engagement or preventing reverse selection.
Symptoms: Inability to select reverse, accidental reverse engagement, grinding when attempting reverse
The output shaft driveshaft flange seal weeps fluid over time, causing a gradual fluid loss.
Symptoms: Oil drip from rear of transmission, low fluid level, driveshaft area oil contamination
GS6-37BZ rebuild replaces synchro rings (3rd/4th standard), reverse lockout components if worn, and all seals. Driveshaft flange seal replaced. MTF-LT-5 fluid used. Bearings inspected and replaced if needed.
BMW MTF-LT-5 every 40,000 miles. E90/E92 owners who track or performance-drive should shorten this to 20,000-mile intervals. Check fluid level every 12 months — there's no electronic monitor.
E90/E92 323i/325i/328i, Z4 sDrive23i/30i, and 1 Series 128i/135i with 6-speed manual.
A GS6-37BZ rebuild ranges $1,900–$2,500 at Chicago Transmission.
Synchro wear — very common on high-mileage or performance-driven E90 gearboxes. Replacing 3rd synchro restores smooth engagement.
BMW MTF-LT-2 (older spec) or MTF-LT-5 (current approved). MTF-LT-5 is the preferred choice for current service.
In some cases yes — if the lockout mechanism alone is the failure, it can be replaced without full teardown.
Free diagnostic, written estimate, lifetime warranty. Chicago's GS6-37BZ rebuild specialists since 1987.
