I was wondering st to why my 1993 Mercury Cougar’s rear end would feeling like it wants to kick out when driving at speeds greater than 45 mph?
Worn shocks will do that, or worn bushings or other suspension components. Have you done a ‘bounce test’?
What shape are the rear tires in, and how are the pressures?
If I understand your description correctly, the rear end wants to go sideways at speeds over 45?
If that’s true, then in addition to the already suggested causes anything that causes a drag on one side would be suspect. This is an independent suspension RWD system complete with upper and lower control arms, stab bars, CV joints, hubs with bearings, and a host of other pieces. There are a lot of possibilities that could cause and imbalance at speed and cause drag on one side.
I good look-see on a rack, followed by a 4-wheel alignment, should get to the root of the problem. It could be as simple as a worn part causing a misalignment.
And yeah, it could also be the tires.
The tires are in good shape; they probably still have half the tread life left on them. When I am traveling down the highway it doesn’t do it constantly but the rear end just sways back and forth very noticeably.
Have you done a bounce test for the rear shocks? It’s easy: Press down hard on one corner of your car and let go. Count the number of bounces before the car comes to rest. If the car bounces even twice, your shock absorbers are faulty.