Hydraulic Efficiency

You are asking a hugely vague question, and aren't really comparing apples to oranges.

but here goes...

What kind of "mechanical setup" are you referring to? My mind goes to a standard trans-axle/transmission/transfer case/differential setup. Which in that case you are looking at roughly 15-20% efficiency from engine to road, depending wildly on the "setup".

If you went hydraulic, with a diesel engine running steady in it's power-band "sweet-spot" lets say at 45% efficiency running a bent axis piston pump at 90% efficiency, turning bent axis piston motors also running at 90% efficiency, with more losses added in for bends/fittings/valves/heat exchangers etc. lets throw out another 15% loss for the "extras" etc etc etc. after doing the "napkin" math, I come up with maybe somewhere around 30% efficiency.

Now...

Keep in mind, I may have tossed a few back, and my rhetoric may be a little off, but there it is.

Cheers!

Not sure that helps the OP much. "......looking at roughly 15-20% efficiency..." presumably means from power in fuel to power at wheels. Seems a bit low, even with a petrol engine at say 30% efficiency. But OP asked about difference between hydraulic and mechanical transmission. It confuses things to then consider hydraulic transmission using a diesel at 45%. The higher engine efficiency could account for most of the change from 15 - 20% to 30%.

My best guess, for transmission only is - mechanical 85-90%, hydraulic 75-85% but somebody out there might have more accurate data.

Codey

yes, you're correct. i meant a conventional 4x4 vs a hyaulic system using the same engine. i was considering power loss from u-joints, gears, ect.

By far the most efficient transmission system on the planet is the dérailleur speed-change mechanism fitted typically to the modern safety bicycle.

But you don't see them on 4x4 off-roaders too often

(BTW appreciate the acute accent. A pedant after my own heart!)