'70 280SE Vibration

[oldbenz]

I need some help!!! I have a '70 208SE that has a harmonic vibration between the speeds of 55 and 65 mph. I have done the following: Had driveshaft balanced and rebuilt with new u-joints and center bearing, replaced the motor mounts and rear wheel bearings and seals. Tightenend and loosened the slip joint nut. After all of that, it still has the vibration.

The vibration seems to be coming from the drivers seat back to the rear of the car. I have talked to several people and have had no success. Anybody???

[ymsin]

I'm exploring the possibilities with keen interest.

Are you able to balance the rear wheels? I know we can't balance the rear of the 126 wheels but perhaps your model might be a little different.

Or it could even be a disproportioned rear tyres, or the rear wheels need a "rimjob"?

[oldbenz]

I have had new Michelins put on all the way around and front moved to back and vice versa. I personally watched all of the tires on the balancer (twice!) and none looked to have a problem with "roundness". I have heard that some shops have a device that balance the tires while on the car. Do you know anything about this?

[johan01]

Originally posted by ymsin
I know we can't balance the rear of the 126 wheels but perhaps your model might be a little different.

Just curious. Why can't rear 126 wheels be balanced?

[ymsin]

OOPS. What was I thinking about?? *slap on the head*

Sorry - I meant to say that the rear can't be aligned. Of course, they can be balanced! I am so wrong, and totally sorry.

Once again - sorry.

[johan01]

OOPS. What was I thinking about?? *slap on the head*

No problem. Its just that its been common practice here that rear wheels are not balanced. Although, I insist on having all four wheels balanced.

I thought it had something to do with it.

[Aaron]

What kind of condition is the front end in? When I say front end, I mean kingpins, control arms, bushings, subframe link & mounts, etc... A badly worn front end will cause a vibration and of course the only cure is a total rebuild.

P.S.--I haven't seen the balancers where the wheel is kept on the car, but when I worked for the MB dealer, we had a Hunter DSP 9000 (I think), which would measure road force variation and runout, etc...Very nice machine. For $12,000 it oughtta be!

[oldbenz]

The front end is in very fine shape. The only slop is in the Kingpin and it is only about .010 - .020 if that. (vertical tolerance)

[Arthur Dalton]

When changing motor mounts, did you change all three.
The rear is under the tranny and should be checked.

[oldbenz]

The rear engine (or tranny) mount looks and feels like it is still in very good shape. I tested by pulling down on the transmission and letting go. It immediately regained it's former position. It's not at all bouncy.

[Mark V]

Vibration felt in the seat is usually due to the rear tires. I'd suspect the balance of the rears, bent rim or something loose back there. Another possibility; did you take the driveshaft apart after it was balanced? If so it may have been put back together 180 degrees out of balance.

Mark

[oldbenz]

The shop that rebuilt the driveshaft marked it with white dots to make sure that it went back together like it was when it was balanced. What do you suggest I try if the rear wheels are suspect?

[ymsin]

The 126 I have used to shudder at the rear. Then, I was having a set of Dunlop tyres. I found that the tyres were the culprit as it couldn't be balanced well. I had the tyres changed to Michelin, and it was so much better, yet not perfect. Then I was informed it was a bent rim. I changed all 4 rims and got rid of the shudder.

[240 Ed]

I am getting a vibe at speed only with power on, and am leaning toward the rear transmission bearing...

The tough thing about driveline stuff is that the sounds/vibes travel so much, you don't really know where there are coming from unless you stick your head down there when it is up on a lift.

Your Michelins are probably balanced. It is the only brand I have seen where one in 10 doesn't need any balance weights. Verrry well made tire.
The only reason a tire would not be balanced on one of these machines is if the operator didn't calibrate the machine in a while.
Typically there is a calibration weight which is screwed onto the spindle, then a special button is pushed. Bingo.

Is any part of your exhaust touching the car?

Have you checked your muffler bearings, and retorqued your exhaust hangers????