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!

in the rear, there are metal dogbone links that connect the spindle to the subframe, did you rebuild or replace any of those? how do they look?
can you define "twitchy"? say, there is a lane with construction and as you cross the road grooves, the car tries to follow them? or are you saying when the road pitches to the outside or on a curve the car tries to shift down the slope? or is it all of a sudden the car just launches one way or the other with no reasoning behind it?

50PSI on an automotive road tire? really? I'd start with fresh soft compound tires and see how it feels from there.

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

It feels like car is moving/rotating about its yaw axis when you accelerate even slightly. It is a bushing on the transmission that is worn out. Not expensive to replace-and not the transmission itself.

__________________
87 300D 265Kmi
Factory rebuilt crate 603.96x engine at 200K

theref, thanks for the reply.

Do you know which "bushing" you had to replace. Or was this a rear transmission mount?

However, my car does not move around under acceleration. My problem is a steady highway speed issue.

My bet is it is just the tires, you say they are old and need replacing. That is way too high on the pressure also. Having the high pressure will affect the ride and handling as well.

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05 SL600 75K
87 MB 560SL 119K
87 MB 300D 180K
83 MB 240D 110K
64 1/2 Mustang
74 Monte Carlo 32K
75 Fiat 124 Spyder
16 Equinox
15 2500HD Silverado

vstech, Thanks for the thoughts. Answers below.

[in the rear, there are metal dogbone links that connect the spindle to the subframe, did you rebuild or replace any of those? how do they look?

...All the metal links are fine. No deteration of the rubber. No axial movement between fasteners. With the disk hub removed and the metal links attached at the body, it is quite easy to move them around and check the condition of the rubber. But they are not cracked and have no movement along their length axis.

can you define "twitchy"? say, there is a lane with construction and as you cross the road grooves, the car tries to follow them?

...On a four lane road, with minimal variation from one lane to the other, when crossing the point where the two asphault patches meet, the car will have a slight side to side jerk.

or are you saying when the road pitches to the outside or on a curve the car tries to shift down the slope?

...No, it is actually very stable in curves

or is it all of a sudden the car just launches one way or the other with no reasoning behind it?

...no, not without reason. I can see the normal road variations, slight dips low spots that cause it to slightly jerk. None of my other vehicles respond in this manner, Chevy Truck, Honda Civic, Chevy Suburban, etc

50PSI on an automotive road tire? really? I'd start with fresh soft compound tires and see how it feels from there.

...understood, this was a test to see if increased tire pressure improved the condition (it did) or made it worse.

if the car tracks into road changes, I'd SERIOUSLY inspect the ball joints, tie rods, drag links, and idler, as well as the steering gearbox!

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

In reviewing old posts of mine, I see I never answered the outcome.

It took new quality brand name tires and a dealership alignment to fix the issues I was experiencing. I have no doubt all the parts I replaced were necessary as they were either worn out or the rubber was soft and deteriorated. Thanks for the help with this issue!

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Turbo300Mercede
87 300D W124
83 240D W123
80 300 TD Wagon W123, 4 Speed from 79 240D, SLS Rear Suspension

I was thinking alignment. I've got a 124 sedan and a 124 wagon, and both recently had an alignment at the same shop, and now both are "twitchy". I really should take them back.

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Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

The initial description sounded like idler arm bushings to me. Also a bad tire can do that to you.

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2001 SLK 320 six speed manual
2014 Porsche Cayenne six speed manual

Annoy a Liberal, Read the Constitution

worn rear subframe bushings can cause the car to rear steer. But if its darting on grooved roads badly it most probably has a steering issue, I had that in my W124 and it was a bad steering box.

Once squared away properly all the way front to back with new rubber parts and a rebuilt steering box it was the best riding car. Firm yet supple and very smooth and stable at speed.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

Sounds like what I was feeling in mine when the caster was out of whack. Alignment fix it.

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Current fleet
2006 E320 CDI
1992 300D - 5speed manual swapped

former members
1984 300D "Blues Mobile"

1978 300CD "El Toro"

Our guy didn't post the exact cause of the problem just a generic solution.

An issue like this is usually caused by too much front toe in / out. What happens is the car is plowing down the road more or less straight. When one tire breaks traction ( like over a bump ) that tire slides in the direction of the tire with good traction. Too much toe out, RF breaks traction , car slides to the left.

The feeling is that the car is gently wandering or squirming down the road. I recently rented a truck and driving off the lot had this feeling. Checked toe at home and found it to be over 1 inch in, adjusted it to sub 1/8" in and it drove much better..

While we are on the subject, a stuck ball joint will give a harsh snappy " can't keep the car straight " feeling. This is because too much steering friction won't allow the wheels to find natural center. Turn the wheel a bit the steering unsticks, the wheels steer too much then stick, steer them back and the same problem occurs over and over.

I've been wondering if I should look at my suspension. Car is 30 years old now but only 180K on the clock. Handles and tracks beautifully but some of that rubber must be dried out by now? When we first bough the car 20 years ago the local MB guy recommended "pulling links" but we never did it. At least I don't remember doing them.

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Brian
87 300Dturbo 180K #14 head still running R-12 SOLD 12/2017
02 F350 Powerstroke 180K
05 Chevy Express 1 ton w/Royal Utility box 120K
08 Infiniti FX-35 40K
15 Golf Sportwagen TDI 35K
10 Sprinter 3500 chassis with a Class A Winnebago on it. 56K

It was very obvious to me that my car needed attention. Keep in mind that I am the type of driver that is "in tune" with what the car is doing and how it is reacting. A casual driver of my car may not have noticed what I did.

However given that my car had right at 200,000 on it, lots of stuff was worn and in need of replacing.

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Turbo300Mercede
87 300D W124
83 240D W123
80 300 TD Wagon W123, 4 Speed from 79 240D, SLS Rear Suspension