W124 Arse Waddles - PeachParts Mercedes-Benz Forum

Bengoshi2000 · #1 01-30-2018, 07:27 AM

I've noticed that the rear end of my '91 300D has an odd feel. The best I can describe it is to say that I can feel a bump in the road in the front, but there seems to be a delay in feeling that same bump in the rear... like the rear end is temporally buffered. Oddly, I feel it in my back and butt, not in the wheel (i.e. I don't need to "correct" the sensation via steering).

The car itself has 115k miles and a set of Goodyear Assurance put on by the PO at about 109k miles. Tires are wearing evenly on all four corners, so I've yet to take it in for an alignment.

I've been under the car looking at bushings, etc. Fronts are all in good shape as are the ball joint boots, etc. Same on the rear... except for the outer rear LCA bushings. The boots are blown/ruptured on both sides. Would wear in those bushes cause the sensation I'm feeling?

The car does need new shocks (and I'm going to assume springs and rear links), but I'm trying to put all that off until the Fall... I need to spend my current $$ on getting the AC system working. Can I get away with just replacing the outer rear LCA bushings (assuming that's the problem)?

jake12tech · #2 01-30-2018, 08:08 AM

I don't really understand what you're saying about it, I'd have to drive it but as a rule of thumb worn bushings will cause rough ride, torque steer ans all kinds of crazy stuff. Replace what is worn and go from there. Not much to think about.

Mxfrank · #3 01-30-2018, 08:09 AM

No answers until you get into it. Could be LCA bushing. Could be any of the control arms. Could be the sway bar bushings. Could be subframe mounts.

dieselmania · #4 01-30-2018, 08:19 AM

Don't rule out tires, a tire in the early stages of tread separation will cause a "waddle" especially at low speeds. You could swap front to rear to rule it out.

chasinthesun · #5 01-30-2018, 08:29 AM

The long body of a w123 I had purchased made this same distinct rolling motion ,mostly at 50 mph and above, frt .shock broken at mount was the discovery.

SD Blue · #6 01-30-2018, 09:01 AM

Rear control arm bushings are a good bet for what you're sensing. You may not see tire wear as rapidly as the front, due to less force from steering, but eventually it will come. This was my experience on a W126 and the W124 is likely the same in that regard.
It's not too bad of a job with a homemade bushing press using all-thread, washers & large 3/4 dr. sockets.

Clemson88 · #7 01-30-2018, 09:03 AM

Quote:

Originally Posted by dieselmania

Don't rule out tires, a tire in the early stages of tread separation will cause a "waddle" especially at low speeds. You could swap front to rear to rule it out.

The tires are my first go to when the tail of a car wags. Wear may provide indications of other problems but sometimes the tires are the source of the waddle.

A seasoned tire tech once told me some tires 'walk,' after being bumped against a curb.

leathermang · #8 01-30-2018, 09:45 AM

Wow.. a thread with ALL good suggestions in it.... good deal !!!!

Clemson88 · #9 01-30-2018, 09:49 AM

Quote:

Originally Posted by leathermang

Wow.. a thread with ALL good suggestions in it.... good deal !!!!

.!

Diseasel300 · #10 01-30-2018, 09:50 AM

As others have already suggested, rubber bushings.

That said, just how bad does it need shocks? If the whole body waddles and rolls when you start giving it the beans on one corner, the shocks can be contributing to your wobbly behavior. Unlike most cars, when you go pushing hard on one corner, you shouldn't have any bouncing in a Benz. If you get jiggling, or a rebound or two, shocks are definitely on the list.

240Dee · #11 01-30-2018, 09:54 AM

Had the same rear end waddle on mine, brand new tires all around didn’t t fix it, but all new suspension sure did! It’s your rear shocks, change em out!

Sent from my iPhone using Tapatalk

Bengoshi2000 · #12 01-30-2018, 03:31 PM

Quote:

Originally Posted by Diseasel300

As others have already suggested, rubber bushings.

That said, just how bad does it need shocks? If the whole body waddles and rolls when you start giving it the beans on one corner, the shocks can be contributing to your wobbly behavior. Unlike most cars, when you go pushing hard on one corner, you shouldn't have any bouncing in a Benz. If you get jiggling, or a rebound or two, shocks are definitely on the list.

When I put it in a curve, she locks in tight and true. A wee bit of body roll, but the "waddling" stops. The first time I threw it into a curve, the sudden steadiness actually caught me off guard.

I say shocks because overall the ride is soft (at least, in comparison, to my previous w123 that had fairly new shocks). I can also get a good bounce going on any corner with little effort.

I'm going to rotate the tires front to rear and see if there's a difference. Might make an appointment for an alignment too.

Diseasel300 · #13 01-30-2018, 05:51 PM

The shocks can be deceptive when they wear. My SDL's shocks were DONE, but it still rode and drove fine. Hardly any weave, which surprised the hell out of me. The giveaway was when hitting a low area in the road such as a valley, there was a huge amount of suspension travel. New shocks firmed it right up, still drives just as straight, but a lot more comfortable on the highway.

torsionbar · #14 01-30-2018, 07:11 PM

Quote:

Originally Posted by jake12tech

I don't really understand what you're saying about it, I'd have to drive it but as a rule of thumb worn bushings will cause rough ride, torque steer ans all kinds of crazy stuff. Replace what is worn and go from there. Not much to think about.

x2, but don't replace what's worn - replace everything. If your car is 20+ years old, every single piece of suspension rubber is dead at this point. Replace ALL of the control arm bushings, subframe mounts, differential mounts, shock mounts, ball joints, etc. For the amount of labor it takes to disassemble this stuff, it's silly to replace a single rubber piece - just tear the whole thing apart and replace it all at once, and then it will literally feel like a brand new car. These rubber bits are not expensive. The shock absorbers are the only things that cost a few bucks, but get good ones like Bilstein, and they'll last a long time.

Then do the same in the front, to additionally include engine mounts, transmission mounts, and drive shaft couplers.

Use quality rubber, Lemforder or Genuine MB. Avoid Meyle, Uro, and other china-made stuff.

nelbur · #15 01-30-2018, 07:45 PM

I would bet it is your shocks. I had a similar rear end twitch over bumps on my w210. Alignment was found to be fine. Just replacing the shocks corrected the problem completely.