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The M70 V12 under the hood of this 1992 BMW 850Ci on Cars & Bids is stock. The gearbox behind it is not. BMW sold the 850i with a factory six-speed, but this car left the factory with an automatic, and it now shifts through a manual transmission from an E46 M3. It's finished in Mauritius Blue Metallic over a tan interior, shows 121,700 miles, and the high bid is $12,000 with the auction ending November 9 at 3:03 p.m. ET.
What Changed Under the Car
The 5.0-liter V12 is rated at 296 horsepower and 332 lb-ft of torque, and that output now reaches the rear wheels through the six-speed from the E46 M3. The seller lists a few supporting parts for the swap: a lightweight flywheel, a custom driveshaft, and a 3.64 limited-slip differential. An aftermarket X-pipe and a short shifter round out the drivetrain changes.
The custom driveshaft is the detail to look at. An M3 gearbox doesn't bolt into an E31 8 Series as a matter of course, and the listing doesn't spell out the clutch, hydraulics or pedal setup behind the conversion. Those are worth asking about in the comments, since the work is only as good as the parts you can't see from the driver's seat.
Wheels and Cabin
The car rides on 19-inch Vossen wheels, a change from the factory look that has already drawn some debate in the listing's comments. Inside, the seller added a Pioneer touchscreen head unit with a backup camera, an Alcantara headliner, and a one-piece shift knob and boot. The original equipment list includes pop-up headlights, a sunroof, leather upholstery, power heated front seats and dual-zone climate control, and the build sheet is in the photo gallery.
History and Known Flaws
The listing shows a clean California title and a clean Carfax report. It says the car was registered to one owner until 2025 and has lived in warm climates since new. The current seller says they bought it in November 2021 and have added about 8,000 miles since. The flaws listed are chips on the front fascia, swirls in the paint, creases and cracking in the leather, and scratches on some interior trim.
Everything in the modification list comes from the seller, and Cars & Bids notes that bidders are responsible for verifying the details. That includes the transmission's origin and how well it was installed. The tinted windows and the 2021 date codes on the tires are also worth factoring in.
Why It's Worth a Look
Manual V12 cars are a small club, and most of the ones that show up got their gearboxes from the factory. We've covered the other end of that conversation before, from a manual-converted Ferrari 599 GTB to a twin-turbo V12 Mercedes S65 AMG. This 850Ci takes the idea in a different direction, with a donor gearbox from one of BMW's best-loved performance cars in a grand tourer that was built to cruise. It's also on the same marketplace as another oddity we've covered, the Brabus V280 minivan: a car whose appeal is the choice somebody made.
At $12,000 with five days left, it's a modest bid for a V12 coupe with a modern manual gearbox. The question for a buyer is what sits between the M70 and that M3 gearbox. The full photo set, build sheet and walkaround video are on the original Cars & Bids listing.
