Most of the following was embedded in another posting that got somewhat off the original subject. So I am re-posting with the hope that the wide experience base of this site can help me with a solution.


My 1987 300D, 124.133, 228K miles has an annoying highway “twitch” / canoe effect where the car ever so slightly pitches side to side with normal variations in the road and during lane changes.

The tires are stock size P6’s, 195-65 HR-15s on stock wheels, but admittedly they are on the way out. They have about 30K miles on them and are now very noisy. I had been running them at 38 psi and they are worn smoothly across the faces. These tires are rated at 44 psi max, but they feel better at 50 psi.

Here is what I have done so far in the following order:

1) Replaced outboard rear carrier bushings, both sides.
Some slight improvement in ride. The rubber seals were torn, but there was still grease inside, so I suspect very little wear had begun.

2) Next:
Front LCA sportline bushings. The sportline bushings are made of noticeably stiffer rubber than the originals.
Front sway bar bushings.
Ball joints (ball joints were dry and needed replacing so I addressed the other items while I was there)
This was a definite improvement. Slightly stiffer ride, little more road noise, but a driving improvement. Still twitchy, but a little less so.

3) Next:
Station wagon rear sway bar links to replace the stock plastic links. (had to shorten the lower bushing lengths to fit)
Rear cradle subframe bushings. I used the two sportline line ones and the two replacement ones.
Took this for a ride and there was a slight improvement. (not worth the effort on the cradle subframe bushings for the slight improvement. While I thought the originals were worn, because the lips did not seem to contact the underside of the body, they were not. But this was not obvious to me until I had them out in my hand. At least the round portion of the bushings was in great shape. Maybe the lips were worn short?

4) Next:
Rear LCA inner bushings
Rear Wheel Bearings
Axle boots
Dirty Road Axle seals / wheel bearing seals
Again an improvement due to the RHS bushing that was soft/worn, but still has a little of the highway "twitch".

I tugged and pulled on all the remaining links in the rear. No torn rubber, no in/out movement. Easy to flex around without the hub in place, but no sign of dry or worn out rubber.

The front tie rod ends and steering linkages are tight. Very little to no noticeable play in the steering wheel.

I performed the bounce test of the shocks. Front is very stiff, cannot “bounce” it. I can push down, it just returns up to ride height. The rear can be “bounced”. It will rise above ride height during the bounce, but settles right back to ride height in ˝ cycle after releasing the bumper.

The car was aligned before any of the parts replacement began as I was under the impression that a miss-alignment was causing the twitchy driving. Before I started any component replacement, I marked the positions of the adjustment cams and put them right back where they were after the front bushing replacement. I have not moved the rear cams. The car does not pull and is not feathering the tires.

Up to this point this is the best the car has driven in the year and half I have owned it. Bought it with 198K miles needing some work and it now has 228K miles. But I believe it should be more stable (no twitch) than it presently is.


This is the first 4 wheel independent suspension car I have owned.

Are they more twitchy with normal road undulations / slight irregularities in the road than a rear solid axle vehicle? Or should it be as stable as a rock under all conditions?

I have ridden in old mid 60’s Corvettes (4 wheel independent suspension) and they did not have this issue, so it must be something I have not yet considered.

I am hoping someone here has experienced this and can point me in the right direction toward the fix.

Thanks for any input / discussions / suggestions!