Sense check on fwd car

[Smitters]

Mg zs, front is up off the ground, wheels off. I start it up, and, assuming the pads are starting to rust to the discs, pop it into first and lift the clutch. My assumption was either, the clutch would slip and i'd have to unbind the pads, or both wheels would rotate.

What happened was one wheel turned, one didn't. I checked, and I can turn the moving wheel by hand. The still wheel was stuck by pads. A couple of whacks and I can now turn it by hand, and see the driveshaft turn too.

Repeat the car start, but still, only one wheel turns when in gear.

What dumb thing have I done, don't know, or overlooked please? Thank you in advance.

[Elliot2000]

It has a differential! It will supply drive via the easiest route if both wheels are in the air.

If both wheels were equally easy to turn then both will turn, if one is harder to rotate then it will rotate the opposite wheel even faster.

[E-bmw]

The rules of physics apply, the power from the (open) diff takes the path of least resistance, there can only be one path of least resistance.

If you had an lsd then both would turn, but yours is open.

[Smitters]

Appreciated. Coming from a 7 with an lsd, and minimal knowledge anyway, I did wonder if the bound disc had somehow knackered the gearbox output.

Cue newbie relief!

[GreenV8S]

Bear in mind that diffs are designed to carry a high torque with a small and intermittent speed difference. If you run the car in gear with one wheel stationary you are effectively turning the diff onto a 2:1 gearbox and making it carry a huge differential speed. That will knacker it much more quickly than normal driving.

[Smitters]

Good to know. Not a regular hobby, just checking it started and ran.