Should New SLX derailleur have this much play....

Lemme go check my new XT for a comparison.

Don't have an exact comparison but pretty sure that's not right - it won't be able to index with that much wobble!?

Yeah, nah mine is a ride old and no way near as much wobble. That SPX wobbles like my three year old XTR. Hence the change.

From your vid there is no chain tension on it and no shift cable attached and the top jockey seems to be in contact with the frame which may well be restricting the movement of the parrallelogram  so there is some play introduced. The derailleur itself doesn't appear to be moving on the hangar so it's just the parrallelogram.

What's it like with the wheel out?

Thanks all , see below for with it without wheel, it does tighten up a bit with wheel on but can't get it to index properly, something doesn't seem right .....

https://streamable.com/zvc56m

That play is different, the whole derailleur is moving there. Is there a washer missing where is mounts to the hangar and is it done up tight enough on the hangar?

Also, if it won’t index then triple check the shift cable is routed correctly through the mech and I mean triple check. It’s very easy to get it fed into the retaining clip from the wrong side!

Does look like it's moving on the hanger but in the mech not the hanger and yeah it's tight , where would there be a washer can't see anywhere that one would go....thanks for the help

Just checked mine and it has a similar amount of play (to your first vid) when sat in the smallest gear. Shifts perfectly.

Thanks maybe there's hope then

Check the cable routing next then - post a pic from the back of the derailleur with the wheel on.

https://imgur.com/a/7miPUvn