Need Help-rear allignment problem 85 300D - PeachParts Mercedes-Benz Forum

300Dguy · #1 10-27-2005, 08:28 PM

I think I've researched every thread possible on this and related subjects but I need help from anyone out there that may have encounterd this problem.

PROBLEM:
MY 85 300D (136,000 miles) has a rear allignment issue that appears to be isolated to the right rear (Passenger) wheel. The car is dog legging with the left front of the car out to the left of the right rear. The inside of the right rear tire is wearing significantly ahead of the rest of the tire and left rear tire is also wearing on the inside but not as bad. This RR wheel also sits back approx 1/2 inch further to the rear of car. I had the allignment checked and all wheels were well in specs except this right rear, which is cocked slightly out away from the car, causing the problem. For you allignment experts, Toe specs for this RR wheel has Specified Range of -0.01 0.66 degrees, and it came in at -0.91 degrees. I next had the car frame checked out at a reputable body shop which measured the unibody every way possible and was advised the frame is straight. Neither the allignment shop nor the body shop could find and tell tail signs of accident damage. The body shop thinks the RR trailing arm could be bent and just not noticable. He suggested changing the trailing arm next.

I just took a tape measure again to car got exact same distance from jack hole to jack hole on each side, but I did find an additional 1/2 cm or approx 1/4 inch longer distance on the right side of the car from the front jack hole to the center of the large bolt into the rubber bushing at the front of the wishbone that screws vertically into the underside of the chassis, and forward of the rear jacking hole.

So, here are my questions and perhaps one of you folks that frequent this site have had this same issue and can steer me straight. I'm trying to avoid any larger task than necessary.

1. Has anyone had this issue and what was the cause?

2. Althought the trailing arm busings appear to be OK from a visual check, and I really can't see much of the bushing at front of the wishbone that is held in place with a large bolt and additional bracket, could worn bushings on that side cause this much of an issue, just from age etc. Should I start with replacing these three bushings? Or perhaps just the one at the front of the wishbone?

3. Has anyone encounterd a damaged/bent trailing arm that appears to look perfect?

4. If I attempt to change all three bushings on that side, should I attempt this repair without pulling out the entire rear axle/suspension assembly.

5. Havn't yet checked the host of this site for bushings, but if they don't have them, any suggestions where they can be obtained other than from the dealer?

Looking forward to any responses, or if you want, private messages.

Thanks much,
Thoroughly confused.

boneheaddoctor · #2 10-27-2005, 08:43 PM

I believe the first place to start would be replacing the bushings in the rear end including the differential mount..20 years they have likely degraded...since there is no adjustment they must be in proper condition to establish if you have other issues...

300Dguy · #3 10-27-2005, 08:47 PM

Haven't given much thought to the differential mount bushing, but it makes sense. If the problem was in all of the bushings/mounts, I would think I might have an issue with the left rear wheel as well??

t walgamuth · #4 10-27-2005, 08:47 PM

of bushings causing this problem. i suspect a bent or rusty rear a arm. i have had one of each. my lovely daughter #2 slid one of my 240s on ice into a curb. it put the wheel at a very interesting angle. a lighter hit might make it hard to see. .25 inches is not a lot but if it is indicative of a bent a arm it would result in the type of wear you are seeing, i think.

of course look at the bushings as bones suggested but if there is nothing to see there, i would look at the a arm.

tom w

Hatterasguy · #5 10-27-2005, 08:49 PM

Replace subframe bushings, diff mount, and shocks if they are original. If the rear still doesn't come up new springs will be needed.

This is a common problem with age afaik their are no rear allignment adjustments on these cars, you just replace bushings.

boneheaddoctor · #6 10-27-2005, 08:51 PM

Quote:

Originally Posted by t walgamuth

of bushings causing this problem. i suspect a bent or rusty rear a arm. i have had one of each. my lovely daughter #2 slid one of my 240s on ice into a curb. it put the wheel at a very interesting angle. a lighter hit might make it hard to see. .25 inches is not a lot but if it is indicative of a bent a arm it would result in the type of wear you are seeing, i think.

of course look at the bushings as bones suggested but if there is nothing to see there, i would look at the a arm.

tom w

I know my LCA bushings on my W116 no longer had the holes in the center but were offcenter from age ...I would suspect much the same with rear tire wear issues....however its possible to have a tweeked trailing arm...but with less than perfec bushings how can that be determined...I know its a catch-22 situation.

300Dguy · #7 10-27-2005, 08:52 PM

I had originally thought of this scenerio by a prior owner as the possible cause. So, are you saying the arm is suspectable of getting bent in such a case, most likely at or near where the axle shaft sits with out bending the wheel or showing visible signs to the trailing arm etc.

dmorrison · #8 10-27-2005, 09:12 PM

As posted replace all the wear items.
Trailing arm bushings, springs, shocks, Differential mount and subframe bushings. Mercedes and fastlane does make a ecentric bushing for the trailing arms. Expensive but made.

http://catalog.eautopartscatalog.com/mercedesshop/sophio/quote.jsp?clientid=catalog.mercedesshop&cookieid=1NB19DAR81NB19DNH4&baseurl=http://catalog.peachparts.com/&partner=mercedesshop&year=1985&product=L2006-16072&application=000013708

But while your removing everything I woudl check all components for damage or rust. The trailing arem are known to rust and present problems.

Dave

300Dguy · #9 10-27-2005, 09:25 PM

This car has zero rust inside and out, and the metal on the suspension looks as new as was off the line in 85. Thanks for the tip on the parts. If the subframe bushing is ecentric, does that afford some degree of adjustment?

From what I'm getting in responses, sounds like worn shocks could even play a role, but I don't see how since they are more of vertical component??
Thanks

boneheaddoctor · #10 10-27-2005, 10:01 PM

Quote:

Originally Posted by 300Dguy

This car has zero rust inside and out, and the metal on the suspension looks as new as was off the line in 85. Thanks for the tip on the parts. If the subframe bushing is ecentric, does that afford some degree of adjustment?

From what I'm getting in responses, sounds like worn shocks could even play a role, but I don't see how since they are more of vertical component??
Thanks

the ecentric bushings are pricey...and need to be installed just the right way to correct...I would stay stock type bushings until you determine something is bent.

Brian Carlton · #11 10-27-2005, 10:04 PM

I typically don't advise against replacing a bunch of worn components, however, you have requested advice on a specific problem..............that being incorrect toe on the rear wheel.

Accordingly, due to the geometry of the rear of the vehicle, changing shocks, differential mount, and subframe bushings cannot have any beneficial effect on your specific problem. None of these items will affect the toe.

The only bushings that will affect the toe are the trailing arm bushings. If these are shot, the toe can deviate from the spec.

Additionally, as others have mentioned, if the trailing arm itself is damaged in any way, the toe would also be affected.

One additional thing to check is the camber. Check the camber of the problematic wheel against the good wheel. Additional info to see if the bushings might be the culprit.

You can check camber with relative ease with a 24" level. Just stand it up against the face of the tire. Pull it off the face until it is dead plumb. Measure the gap between the tire and the level. The gap can be converted to degrees. If you need assistance, post the gap and I'll calculate it for you.

PaulSpringmann · #12 10-27-2005, 10:33 PM

The rear trailing arms can be bent; I bent the right rear trailing arm on my 126 280SE during a Wisconsin winter when I spun out and hit a curb years ago. I didn't think the impact was that bad, but the camber on that wheel after the epsisode was out of wack. I replaced the arm with a used one and everything was back to normal. There were no signs stress on on bent arm.

300Dguy · #13 10-28-2005, 07:54 AM

Paul,
When you replaced the bent trailing arm, did you also renew any bushings? How many miles were on the car at the time? After reading all the good responses, looks like I should go ahead and replace the trailing arm that is suspect, and do all the bushings while I'm at it since I'll be pretty far into a labor investment at that point and while the car is in exceptional shape overall, it is 20 years old and I would imagine bushings can deteriorate just from age alone.
Thanks

boneheaddoctor · #14 10-28-2005, 08:43 AM

I'll agree with Brian that certain rear bushings will not effect toe settings. However I am a firm believer in if you do a couple bushings due to age you should do them all at that end of the car. Because at 20 years old if they have not failed they could do so soon. After all they are rubber and rubber does not last forever. You will already have it halfway appart why not just finish renewing all the bushings while you are in there.

PaulSpringmann · #15 10-28-2005, 09:02 AM

I don't remember the specifics as it was 10 years ago. But probably around 225k mi on the mileage when I bent/replaced the arm. I did replace the bushings in the control arm; this is easy when the replacement is sitting on your garage floor.

You might as well replace your subframe bushings/diff mount too as you will have to partially drop one side of the subframe in order to get the trailing are bolts out (at least this is how it works on the 126). If the subframe bushings are original, you will be very pleased with the improvement in hiway driving.

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