Car Swaying left to right...

[md.]

Hoping to get some advice on snaking!
2014 ford bmax good tread of tyres all round no obvious loose ball joints, track rod ends etc.
Getting upto speed and the car feels like it's snaking at the back end and literally makes you feel travel sick swaying left and right and seems to get worse as you build speed. Just changed nearside rear shocker (could only get one last minute today) and changing the other one tomorrow as read it could be that.
Tyres seem all good with no bulges or anything.
Is there anything else obvious to look for at all?

Cheers!

[Rockets7]

Rear subframe ok?

[md.]

Sounds like a ramp job that is it?
What would I be looking for on the subframe if not, bushes, corrosion?

[GreenV8S]

Get a competent mechanic to put it on a ramp and give it a thorough check.

Some of the causes for thet type of behaviour are safety critical, and you aren't going to spot it by guessing at faulty components you could swap to fix it.

[md.]

Thanks, that's on the to-do list tomorrow. Definitely won't be moving off the drive now until its got to go to the garage!
20odd year's of driving and never experienced anything like it!

[Peanut130]

Take it for a MOT then tell them what the car is doing it would only cost the price of a mot
and whatever is wrong with it

[GreenV8S]

Oh by the way - did you check the tyre pressures? An under inflated tyre can cause that sort of instability at speed.

[md.]

So to update this. This morning I changed the second rear shocker and checked all 4 tyres as a last ditch attempt before booking it on the garage and voilà, touch wood it seems to be sorted! I'm telling myself it must've been the shocker(s) as surely a 3-4 psi pressure loss in one tyre couldn't have done that.....
Bit of a weird one!

[Tony1963]

It’s not weird at all. One new damper and one worn damper on the same axle is asking for trouble.