1998 MGM GS - Poor Ride Quality - This car is driving me insane!

[MercuryMilt]

This is my first time posting and I am here because I am at my wits end.

I have a 98 MGM when I got it, I loved the soft ride, but then all the usual front end problems appeared, worn ball joints, squeaky bushings, bad shocks, seized tie rods.

After replacing all of those bits, the ride quality is so harsh, the slightest bump is bone rattling, teeth chattering, in a word it is rough.

I have since changed the upper and lower control arms, all of the steering components.

I am sure the car also now sits higher and it feels like it has a weird vibration I have also noticed that when I grease the suspension it feels slightly better for a short while but goes back to feeling harsh in no time at all, all the roads around me are dogshit also.

Upper CA: MOOG RK80709 / MOOG RK80708 (with respective ball joints and bushings)
Lower CA: MEVOTECH GK80394 / MEVOTECH GK80393 (with respective ball joints and bushings)
Shocks: KYB KG4550 / KYB KG5507 (KYB Gas-A-Justs) (I tried KYB 344424 on the front and still no good)
Springs: Factory 32CC (I tried MOOG 9046s and they were too stiff)

Wheel Hub: TIMKEN 513202



I am able to compare the car to friends with a 1998 LS and a 2002 GS and my car is by far the bumpiest ride.

I am wondering if there is an obvious error I have made or some kind of adjustment that I could try to get the ride more plush?

[sly]

Check the RockAuto list of shocks.

https://www.rockauto.com/en/catalog/mercury,1998,grand+marquis,4.6l+v8,1305201,suspension,shock+/+strut,7556

Anything in the top section is "stock" ride. Gas-A-Just shocks are considered "performance" shocks and will be harsher. The KYB Excel-G would be better for the plush feel. Gabriel Ultra works well too. That's what's on my wife's car. The Monroe Monro-Matic feel like worn out shocks and are a bit too bouncy for my taste. So yeah... don't use performance shocks if you want the floaty ride.

[gadget73]

When you tightened the bolts up for the upper and lower control arms, did you do it with the suspension at ride height or with it up in the air? If you did it in the air, thats probably why The rubber is bonded to the bushing shell, and if you tighten it with the suspension at full droop it adds a fair bit of extra spring load to the system. . Loosen the upper and lower control arm bolts, put the car on the ground or on ramps, then tighten them and see if that fixes it.

[tbear853]

What size wheels and tires and what pressures are you running?

I had 16x7s with 225/60-16s, but since 2015 have used 17x7s with 235/55-17s, but still run 40-ish psi. Still have Bilstein HDs and Addcos installed in '02, but have effectively removed the Air Lift assist in rear springs by simply not replacing the cracked open bags. Have a new set of bags stored, but simply no need & car rides better without them.

[Arquemann]

The Monroe Monro-Matic feel like worn out shocks and are a bit too bouncy for my taste. So yeah... don't use performance shocks if you want the floaty ride.

I got new KYB Excel-G's on mine, they feel just on the edge of being too harsh for my taste. Sounds like I should've gone with the Monro-Matics then