Forgive my ignorance. I don’t even know enough terminology to search for this problem properly.

Got my bike out tonight to give it a once over before the weekend trip and found that it’s not freewheeling. Push the bike forwards and the pedals turn. Try to pedal backwards and the rear derailleur travels to the end of its spring travel. Rear wheel off and the cassette won’t spin, just a small amount of travel before it locks.

Apologies for the rubbish description… It’s a 10 speed Shimano SLX cassette from a stock 2012 Giant Trance X2.

Any quick fixes before Saturday for someone with a clear lack of spannering skills?

it’s not the cassette. It’s the freewheel in the hub.

Sounds like a freehub problem.
You maybe lucky and it just stuck in place if you have not used it for a little while
You could try forcing the cassette round anti- clockwise and see I it frees off

The cassette sits ontop of and is separate from the freehubody that allows you to freewheel

I had a 2012 SLX freehub fail as you describe, just stuck. The wheel was only a couple of months old so it was warrantied. Essentially the freehub is gubbed, it’s quite an easy fix for your LBS if you need it in a hurry.

As a bodger and only basic maintenance able person I always understood that Shimano freehub bodies are not serviceable, they are just remove and replace.

If you cannot get hold of and fit a new freehub body, there is a way of flushing it with light chain oil. I think it involves removing the body and dribbling oil into it from outer end to inner until it starts to seep out as filthy carp. This may free things up, but be aware that a sudden seizure can be very nasty if going at speed.

Have a look around on the web. Park tools site used to be quite good, but not so much now.

That should have read ‘crap’. Don’t look for ornamental fish coming out of a freeing, although that would explain the seized freehub.

Take the cassette off and have a look, plus check jockey wheels.

Thanks for the clarification of freehub vs cassette. Goldfish would explain it but I think it’s a long shot frankly, even with all the wet weather we’ve had.