Yup, drivetrain losses can be truly horrendous.
I had a Bentley continental flying spur in the workshop today.
Just blast cleaning and painting the little cosmetic Bentley emblems on the truly huge calipers - part of a bigger service and check over, but it needed doing, as the calipers were looking scruffy.
Simple enough job, also gave the calipers a really good clean, and ground the ridge off the discs all round.
This is a simple enough job on most motors.
I use an angle grinder with an abrasive disc or flap wheel, and either run the car in gear, or get an assistant to turn the disc using a rechargeable drill or similar.
It's a cosmetic job really, but since I am there checking the brakes, it's nice to tidy things up.
On this car, the static transmission drag was truly phenomenal.
I now understand why it uses so much fuel.
None of my power tools could turn the wheel continuously ( remember, all of the wheels were off the ground, and the trans in neutral.)
The drag was amazing !
I had to resort to running the car on the stands to turn the wheels while I dressed the discs, with all manner of weird rattling and knockings coming from the brakes ( even with traction turned off!).
It amazed me how much effort it took to turn the transmission the losses must be immense - never underestimate them.
Anyway, job done, brakes checked, discs re-dressed, calipers cleaned, emblem pieces blaster, painted and refitted, and the wheels cleaned and rotated.
Job done. But by eck - it's a meaty motor!