Fluttering noise on acceleration

[DanielG]

Hi -- the noise continues.

Question: Is there an SRS sensor in the differential (there is some sensor there -- I have seen it)? If so, could this be a cause of the fluttering noise in the car -- specifically, the SRS light in the car has been lit since I bought it -- if the SRS system is tied to the differential could a problem with the differential cause the SRS system light to come on; and working the other way, if it is a faulty sensor in the differential could it cause the differential to behave badly because the car thinks that a crash (or other) condition is existing?

[Richard1]

Wouldn't the SRS system be tightening the seat-belts if that was the cause? If my SRS light were on constantly, I'd want it fixed immediately. As for the fluttering, does it happen when the car is warmed up, every time you go fom an acceleration or only when the car is cold?

[DanielG]

In a 1986 560sl the seat belts do not have srs sensors -- and the srs does not tighten the seat belts - that is another system. I would want it fixed too, but not at the cost that every mechanic (dealer and indy) project -- it is only a "supplemental" system, and the main safety comes from the seat belts and the car crumple zones. By the way, there is no way to tell exactly what is wrong with the system (no OBD) -- therefore it would be a hit and miss part replacement exercises -- very costly!

Flutter happens everytime I accelerate from a stop and pass between 1500 and 2000 rpm (when the gear shifts) after that no fluttering until I stop and then accelerate past that rpm zone. hot or cold

[DavidSoine]

So it is only on the first 2-3 shift? Does it do it if you do a 1st gear start? I assume your car normally starts in 2nd gear...

best,

Dave
87 560sl

[DanielG]

I tried accelerating past 1500-2000 rpm in each of the different (forward gear) positions on the shifter -- and I got the flutter each time.

[ericgr]

I once had a fluttering noise that I spent some money on trying to solve. It turns-out it was the fan shroud. The engine will move around on acceleration and a slightly out of adjustment fan shroud will cause a fluttering sound.

I realize the thread has focused on involved solutions to the problem and it may indeed be an involved problem. However, my experience dictates that mechanics miss these kinds of simple answers. If it were me, I'd move the fan shroud a bit (check adjustment) and see if it changes. I'd check my viscous fan clutch, bolts, etc at the same time.

[DanielG]

Thanks, but no, that was not it -- its the axles and bearings

[DavidSoine]

Did you get it fixed?

-ds

[DanielG]

No -- but when it was put back together the noise was gone for a day (they had put some lubrication on the bearings) - so I am pretty sure the last diagnosis was correct. Had this been diagnosed correctly 18 months ago I would most certainly have fixed it and would have enjoyed the car just a little more -- it was already a lot of fun!

Ooh $830 a side. I know not every one is mechanically inclined. But I have found rebuilt axle shaft assembles anywere from $79 to 120 a side. They come with a life time warranty. My 380 actually has the same problem on the left side.