Rear wheel moving under load

Took my colnago out of attic for ride now that weather turning better. Took off wheels to give everything good clean and lube before riding out today. Straight away noticed gears/chains jumping. Then when going up a hill and especially when getting out of the saddle the gears started jumping and the rear wheel started to move until it sat tight up against the caliper and stuck hard. Nearly fell off bike when it locked up suddenly. Got off and adjusted wheel and tried again. Wheel started moving again. Any ideas on what is happening?

Total protonic reversal.

More info needed, could be a lot if things from bent dropout to worn cassette.

Quicke release not done up properly... if your bike has horizontal dropouts, I would recommend an internal cam one, Shimano or Campagnolo type

Thanks for the advice guys. Cogs are fine and qr is nice and tight. It's a 9sp ultegra wheel. Its doing this since putting wheel back on and can't for life figure it out. I've retightned the qr and will try again tomorrow. But the gear slipping is damn frustrating. It's not even going in one direction. Seems to move up AND down the cogs. As though something ain't straight.

the QR might be tight but not tight against the frame. it might be tightening up against itself.

take a look and if thats the case just put a washer on the axle to fill the gap on the inside of the frame. ive had this a couple times before.

if the wheel is moving then it's not tight in the frame and this, to me, seems like the most likely cause.

Inspect dropouts for cracks.

Take skewer out of wheel, check your axle isn't broken: something very similar happened to me, axle had sheared and just fell out in bits either side when I removed the skewer.

What Skully said. Happened to me too.

Take skewer out of wheel, check your axle isn't broken: something very similar happened to me, axle had sheared and just fell out in bits either side when I removed the skewer.
Thanks for this. ill check that tonight. I assume this wont be apparent from just loosening the qr's to remove the wheel? I also have to pull out the skeweres themselves.

ive had that broken qr thing, wiggle the wheel left to right, there will be play like it has loose cones.

Yep, unscrew the end of the skewer and pull it out. Worth checking, I may be totally wrong.

Quicke release not done up properly... if your bike has horizontal dropouts, I would recommend an internal cam one, Shimano or Campagnolo type

This! I found the open cam type would slip in horizontal drops no matter how tight I got them. Had some embarassing falls in clips as a result.

Thanks for the advice guys. Cogs are fine and qr is nice and tight. It's a 9sp ultegra wheel. Its doing this since putting wheel back on and can't for life figure it out. I've retightned the qr and will try again tomorrow. But the gear slipping is damn frustrating. It's not even going in one direction. Seems to move up AND down the cogs. As though something ain't straight.

Put it on a stand and adjust the rear mech high / low gear stops till it shifts smoothly... worked for me. Though if the cogs are worn too there's no way to stop it slipping.

Checked the qrs and all seems fine. Haven't tested it up any thing too steep yet but seems to be fine on the inclines. Chain still slipping up and down before it settles but teeth seem fine. May change them anyway as they aren't an expensive item