Rear End unstable at high speed - PeachParts Mercedes-Benz Forum

latief · #1 10-31-2009, 06:01 PM

I just had the car aligned, and the problem is not fixed. around 70mph, the rear of the car does not feel stable. it feels like it is shifting left and right. I had this problem ever since i bought the car, but i thought my new tires, and alignment will cure it since my steering was way-off originally.....

I am at 180,000 miles......

what is the first thing to look at ?

thanks,

scottmcphee · #2 10-31-2009, 06:48 PM

You probably need new suspension links in the rear. You have similar mileage as mine and I just did the job. If want to be fussy find the most worn link, probably the top or forward one. But for the money you can buy a whole aftermarket set for pretty cheap. So I replaced 4 per side, and put new shocks in while I was at it.

Amazing difference, now my car has a tight ass and no steering wander back there.

latief · #3 10-31-2009, 09:18 PM

so i guess i just wasted an expensive alignment.....i wish i new this before i did it !!!

anyone one have a pictures of the suspect parts?

thanks,

yal · #4 10-31-2009, 10:52 PM

See last two post of this link.....
http://www.peachparts.com/shopforum/showthread.php?t=264319

long-gone · #5 11-01-2009, 12:49 AM

Not sure about this, but when you get an alignment on a Mercedes (a W124) don't they have to align the rear wheels as well?

compress ignite · #6 11-01-2009, 01:21 AM

Thatsa why Youse takka to Ta Dealer! [To have It Aligned]
'After you replace All those 15 to 20 year old Rubber Components!

Here's gsxr's rear link compendium:

http://www.w124performance.com/images/W124_subframe/rear_links_all.jpg

#7 11-01-2009, 08:56 AM

Perfect example of why you should look before you leap. You need to CONTINUE to look before leaping while working through this problem. DO NOT go replace all the links in the rear. LOOK first. All you have to do is examine all the dog bone joints looking for rubber pooching out of the joint. Any dog bone with rubber pooching needs replaced. Also check the subframe mounts that mount the suspension subassembly to the body of the car.

Assuming that the car received a good four wheel alignment, if you find a bad dog bone or two and replace them it will have near zero effect on your alignment.

Just so you know, any alignment tech worth minimum wage knows to inspect all components before alignment and release back to customer.

scottmcphee · #8 11-01-2009, 10:14 AM

Only one of the four rear links are alignment adjustable with an eccentric bolt... it controls toe-in. Everything else is fixed geometry, so the rubber really matters. With just a couple links off it's amazing how wobbly that rear wheel gets.

The rubber also dampens shock, like torsion shock absorbers at every joint. This is why its important to have the weight of the car on the axle when you tighten the links into place, to establish a neutral sprung position.

I am putting off alignment until all the suspension and steering pieces I want to replace get done, then align. That's the icing on cake.

latief · #9 11-01-2009, 10:31 AM

I did look at this before sending it in, but since i am new to this car, i did know what to look for...the car is solid in the back, shocks are excellent, and there is no wheel play or metal-to-metal noises.....

The alignment shop i took it to is a mercedes shop, they are better than the dealership, I know that for a fact. look where i live and you would know where i took it...i did not mention any specific problems while i was there because i was assuming this was an alignment only issue since my inspection yielded no results....but to be fair (to myself), they should have taken it to the highway since they are most likely familiar with these kinds of problems...

so what do you advise me to do? I am sure the problem is what you guys mentioned, and I am capable of doing the work my self, but I don't want to pay another $90 for an alignment after that.should I take it to the alignment shop again? they will probably want to replace everything back there since it looks original ( I cannot afford that now) ..i would be lucky if the alignment stays intact as Larry mentioned, but that depends on which links/bushings are the culprit, correct?

thanks,

latief · #10 11-01-2009, 10:36 AM

Compress ignite,

where do you get that gsxr's kit from ?

Roncallo · #11 11-01-2009, 10:56 AM

Quote:

Originally Posted by compress ignite

Thatsa why Youse takka to Ta Dealer! [To have It Aligned]
'After you replace All those 15 to 20 year old Rubber Components!

Here's gsxr's rear link compendium:

http://www.w124performance.com/images/W124_subframe/rear_links_all.jpg

I have most of these parts used in stock from a 45,000 mile SL600. Let me know if interested.

scottmcphee · #12 11-04-2009, 02:49 PM

Ebay, I got all 8 links, $145 + ship. vendor FCP Groton, I've used them before too. Ended up needed an update kit for bolt bushings for myear W124, so get those up front if you're doing the job.

MattBelliveau · #13 11-04-2009, 03:51 PM

Is this just a simple unbolt remove replace kind of job? I fear I need to do the same. Any difficulties or things to look for?

ps2cho · #14 11-04-2009, 07:46 PM

I bought my kit 2 years ago..yet to do it...I started but ended up needing updated bolts as the stock ones are different from the ones you need to complete the repair as they updated them. FYI.

scottmcphee · #15 11-04-2009, 09:36 PM

You can do the job, but you'll need every piece of socket extensions, wobble joints, different depths of 17mm and 19mm sockets, an air impact gun is handy...Just getting at the bolts is half the game. You'll need a short pickle fork ball joint separator - because there is one of those on one end of one of the bones. Once you've figured out one side, the other is easier of course. But systematically remove and replace one bone at a time. You'll see that you have to remove some to get at others, which dictates an order. Only one of these has an eccentric nuts on it for alignment. Put it back the way you found it and hope the toe in is good enough.

The most important thing is not to tighten the bolts until you rest the weight of the rear lower control arms onto blocks, so that the rear axle is level. Put blocks under both lower arms, full weight of the car on them. Tire rubber off the ground.