whole lotta shaking going on

[Joe]

My '71 280SL automatic has had a problem with shaking when I hit a bump. It is sort of hard to describe, but the car sort of jumps sideways a slight bit. The car tracks just fine, and the steering seems ok.
The receipts for previous work came with the car, and on the most recent one the mechanic noted the king pins need replacing. I guess that is one reason the person sold the car.
I bought king pin sets and set about yesterday to put them in. I got one side off and found there is no slop at all in the king pin. What a pita that is. Now I have to put the thing back together!
The shock absorbers are shot. The idler arm doesn't have any slop in it, and the tie rods seem fine. I removed one motor mount and it looks fine, so I assume the other one is ok.
The A-frames are nice and tight, no play at all in them. The steering shock is ok.
I can't see any loose bolts or nuts, and can't find slop by moving a tire with the wheels off the ground.
About all that is left to check, that I can think of anyway, is the steering box and the transmission mount.
How do I check out the steering box, and can anyone think of any other likely suspects? Would bad shocks alone cause the shaking?
Thanks in advance for any advice.
Joe

[JimVillers]

Joe .... You didn't mention checking the read differential mount in the trunk.  It can cause some of the symptoms that you described.  If the bump plate of the mount is against the trunk, it is bad.  Also try lifting the center of the differential with a jack to inspect the rubber.

Jim Villers
190SL, 230SL 5-Speed, 190E 2.3-16 Kompressor, MGB 5-Speed

[nick350]

Jim is right, I had exactly what you describe. I had that big rubber changed, the one that no one ever changes because its a pain and is expensive ( relatively ). I also had all the rubbers done that effect road texture "noise" and it has made all the difference. I used to think that the car was going to crack in two before and now it's really good. It's funny how after all that I have changed and got used to, it makes me wonder what was in my head when I bought my car, it must have been a stinker!

Rubbers / tyres are the things that for me have made the biggest difference. For example, my old tyres, the ones that were on it whilst it sat for a year waiting for me come along had a flat spot on them and of course this made my ride horrible. I was worried that I had bought a ****ty car and thought that I would never be able to get rid of it. In fact in some ways this forum didnt help because as much as the information is fantastic, my early days had me worrying that there was just too much to do. I have had a lot done but in a way even if I had bought a better car I dont think that I would have gotten away with doing much less than I have. I have kept everything standard on my cars except for electronic ignition and even though I dont think this is ultimately the best I will do, I do think that its a good departure point and so that next time I change the tyres I might have something wider put on. I also chose not to use poly bushes, only as I said because I wanted to just start from zero as it were. Anyway, there is some claim that they make the ride a little harder and I quite like the lollopy ride I have with my car. So, relax and do think of the things that will make your ride more comfortable and you'll be set.
Nick350
r107 SL red
w113 SL white

[Joe]

Thanks, guys. I looked underneath the differential and can't really see much. Can I remove the bolt and round plate in the trunk to determine the condition of the mount, or must I remove the exhaust system and look from underneath? What do I look for if I simply jack up the differential?
Joe

[J. Huber]

Joe. I had that sideways jump -- discovered my rear shocks were really shot. I changed them (along with diff. mount) and no more jump...

James
63 230SL

[jameshoward]

Hi Joe,

I've just changed the diff mount. I note Paulr's comments, but I must say that either I did something terribly wrong and have screwed the whole thing up, or Paulr just had a bad experience with his car.

First, the mount was about GBP30, or about $60. I got it from SLS in Hamburg, who I use for all my parts because they've always seemed to work out the cheapest and their service is bar none. I ordered this in case mine was shot. I was repacking the rear wheel bearings anyway, so thought I'd check it out.

To check the mount, I first removed the plastic cover - the thing that costs more than the mount! 2 philips screws. I then loostened the large bolt and the 4 smaller ones. Car was then jacked supported under the diff. This has the effect of taking the pressure off the mount. The pictures show the mount was pushed up out of its proper place because the rubber and metal that comprises its construction had separated.

I then removed the large bolt, the 4 smaller ones and with a bit of fiddling around, lifted the mount out. Mine was utterly shot; effectively in 2 bits. The new one didn't go on quite so easily; I had to mess around with the jack and some axel stands. You also have to identify the little lug in which the metal plate must sit. Basically, put the new one on in the order the old one came out. Note also that the mount IS NOT SQUARE. The bolt holes will ALMOST line up if you get it wrong, and you'll be convinced you have it close. I played with this for a while before thinking to check the geometry. It's a rectangle. With that sorted, the 4 corner bolts went in quite easily. I tightened up the big bolt to the correct torque as in the BBB (the whole procedure is in there), dropped the car down, and replaced the plastic cover. Job done.

All in all it took about 45 mins. I thought it was the easiest thing I've had to do on the car. It was certainly rewarding compared to the fight that other jobs have been. It seems to drive so much better.

Happy to answer any more questions. In sum, remove the plastic voer and jack up the car. If your mount rises up some way into the trunk, I think you can safely say it could be replaced.

Hope that helps. (Let me know if you need the torquing values)

James



I examined my mount and found it was in a poor state. I've attached a few photos to show you. See how it has risen into the boot space.

Download Attachment: DSCN1215.jpg
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Download Attachment: DSCN1218.jpg
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[waqas]

Interesting.... I've been meaning to change that rear mount due to the clunking that comes from the rear-end when I go over bumps... but could it also have something to do with the [very slight] direction changes I randomly experience at higher speeds...?  I think I'll try to replace it next weekend and find out what happens.

Oh, and the mount that's time-consuming to replace is not this trunk mount, but rather the tubular mount that goes into the 'hinge' of the swing axle...

WAQAS in Austin, Texas

[68_white]

It seems that I have the same problem.

Could you add a photo of your newly installed trunk mount if you have the time. It would help me see the difference.

Thanks.

HARRY

68_WHITE

[jameshoward]

Harry,

Aside from the fact that I apparantly referred to the wrong mount (!) it made a hell of a difference so who cares?

I am away from the car at present so no photos right now. If you have a concern about the mount I was talking about, just jack it up by the diff and see what your mount does. If it pops up like my photo, consider changing it. The new one sits flat and neat in the correct position your will sit in when the axel is supporting the weight of the car (because the axel support that the mount sits in will be applying a downward force on the mount holding it in place and flat).

It's an easy job and quite cheap to do.

James

[68_white]

I will try that. Thanks James.

HARRY

68_WHITE

[waqas]

quote:Originally posted by waqas

Interesting.... I've been meaning to change that rear mount due to the clunking that comes from the rear-end when I go over bumps... but could it also have something to do with the [very slight] direction changes I randomly experience at higher speeds...?  I think I'll try to replace it next weekend and find out what happens.

I replaced the trunk mount this weekend... amazing difference! Took less than 30 mins, and only had to support the diff. with a jack underneath. Of course, the clunking is all gone, but the random direction changes at higher speeds also seems to have diminished!

Next up: replacing the sub-frame mounts and torsion bar rubber... I can't wait to drive this car with NO clicks and clunks from the suspension  :evil:

WAQAS in Austin, Texas

[ja17]

Hello,
Bad rear shocks will make the car do a kind of "hulla dance" when you hit bumps.

Joe Alexander
Blacklick, Ohio

[waqas]

Hmmm.... there did seem to be a little 'hula-ing' going on in the back... is there a more scientific way of determining that shocks need replacement?

WAQAS in Austin, Texas

[J. Huber]

Hey Waqas. I think the most scientific way would be to unbolt and remove them and see what kind of action/resistance you have. It is not too hard to remove them. Another way is a push down on the fender. I think the car should not go down much -- and should return promptly. Maybe Joe can clarify this one -- he had a test I used a few years back. Mine were kaput.

James
63 230SL

[wbain]

You might also look at the horizontal differential mount bushings, which is the 13th picture down in this posting

http://www.m-100.cc/forum/index.php?topic=2276

Check out some of the other pics too, pic 11 for trailing arm bushings, pic 9 for lack of grease on the swing axle joint, pic 7 & 8 for the hinge joint.

These are old cars and need to have all the rubber checked.

IMHO

Thanks

Warren Bain 1965 220S, 1989 300SE, 1989 420SEL, 2020 Ford Crown Vic Police Interceptor

[ted280sl]

The sub frames mounts can make a huge difference.
Ted 1969 280sl

[ja17]

Hello,

You can test the rear shocks by doing a bounce test on each corner of the car as described. You can also disconnect the shock at the bottom and see if it still resists pull and push. The nitrogen filled original gas shocks push extended and also resist pull. Let the shock extend all the way and check to see how much "free play" at the extended end and see if they still are pushing.

Joe Alexander
Blacklick, Ohio