My 83 300SD has recent alignment done recently by knowledgable shop. It still doesn't track right on straight roads. Feels like it's floating, possibly directed by the rear end. From what I've read, it may be a symptom of subframe and or trailing arm bushings requiring replacing. Please point me in the right direction. Thanks.

John

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Certified Registered Nurse Anesthetist (CRNA)
2002 F250 powerstroke with Plantdrive WVO conversion
1983 300SD 190K miles ,sold
2006 E320 CDI

The rear trailing arm bushings will definitely cause that behavior if they are shot.

But, you'll need to get underneath and really pry on the arms to determine if they are the culprit or not. Generally, they are reasonably durable. I was considering doing those bushings on the SDL, but their condition didn't warrant it.

Generally, your first thought on the suspension isn't the real problem...........so be careful in diagnosis without data.

Brian;

What else should I be looking for. It's hard to put a finger on how the car handles. Steering wheel play is 1/2". I replaced all shocks, UCA bushings and ball joints, tie rods appear in good shape, fairly new tires inflated properly. Thanks for any help.

John

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Certified Registered Nurse Anesthetist (CRNA)
2002 F250 powerstroke with Plantdrive WVO conversion
1983 300SD 190K miles ,sold
2006 E320 CDI

.........well, it's even more difficult for me..........

It appears that you've done some work on the front end and that it shouldn't be wandering much due to any components up there.

I would check the upper ball joints, however. Most folks neglect these because they are generally lightly loaded. But, they will cause drifting if worn.

The trailing arm bushings should be checked in the rear.

Now I'm no expert by any means, but whilst I was trawling for info on my problem, I came across something about someone complaining about 'swaying' and then having it diagnose as a loose Guide Rod.

Perhaps that could be your problem as you don't mention anything about changing that particular part?

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1987 300TD
1984 300D
755,000 KM and going strong
BC Canada

My thought on the guide rod is that it will cause the vehicle to pull if it's loose. Without a pull during braking, I don't see how it can be the smoking gun in this situation where the vehicle just has some squirrely handling characteristics.

Rear sway bars will make a very surprising wallowing feel on corners.

Tom W

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

I just looked through my printouts and what I mean to say was Idler Arm. Here's the thread where it was discussed. Now this may or may not be the thing, but the symptoms do sounds similar

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1987 300TD
1984 300D
755,000 KM and going strong
BC Canada

If the alignment shop added air to your tires, that will make it feel like it's floating. I had the same experience when I got new tires and had an alignment done, they pumped in around 40+ psi whereas I usually go 30/34 F/R.

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http://farm8.staticflickr.com/7271/7...144c3fc1dc.jpg

If they got the toe-in wrong on a W126, that can make the car squirrelly in the front end. If you hit a wet patch of road and it starts shooting to one side and then the other, that can be due to insufficient (and maybe excessive) toe-in.

Take a stick wide enough to span the front tires and make sure the front edge of the two wheels is less wide than the back edge. It is a rough measurement, but can indicate big errors in alignment.

Ken300D

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1982 300D at 351K miles
1984 300SD at 217K miles
1987 300D at 370K miles

Alignment shops have a hard time with Mercedes. The last one I went to couldn't do a good job (pulling, took back, then tire wear) and missed a bad tie rod.

The one I just went to said that Mercedes are difficult but that they have a guy who specializes in them. The found the tie rod, did a good alignment, and the car feels a lot better. The sway you describe is what I felt before I had it done.

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1991 350SD (updated rods)
Biodiesel B100 when I can find it.
Dino when really cold outside

Tom;

That's a pretty good description of how the car feels. I don't notice it on corners, mostly on long straight roads. Tomorrow I'll crawl under the car and check the idler arm, ball joints, trailing arm/subframe bushings, etc. Thanks for everyone's suggestions.

John

__________________
Certified Registered Nurse Anesthetist (CRNA)
2002 F250 powerstroke with Plantdrive WVO conversion
1983 300SD 190K miles ,sold
2006 E320 CDI