Fluttering noise on acceleration 86 560sl

[DanielG]

I posted this in the SL forum -- with limited results. Sorry for the double post, but if anyone has some insight into this problem I would appreciate hearing from them.:

For some time I have been hearing a noise in my 1986 560sl. It occurs in the right rear of the car during acceleration. It sounds like fluttering and occurs only at acceleration from a stop -- seems to get louder as the acceleration continues -- but does not seem to occur at other accelerations (such as when passing other cars or accelerating to higher speeds).

At first I thought it was the muffler, and as I had been told that it had a small hole, I went ahead and had it replaced. When I continued to note the sound, I took the car to the muffler place and asked if there was a leak -- they put the car up and checked and there were no leaks.

I took it to my independent mechanic who could not locate the problem. They put a lot of time and parts into the search -- for which they indicate on the invoice that they put 10-15 hours in (I think they put more time in and were embarrassed to put the time down -- they had the car for 2 weeks) and charged only 4 hours -- they had each of their 4 or 5 mechanics give it a try and no one could solve the problem. The invoice details the different things they tried:

"Fluttering noise on medium to hard accelerations--

from start check over replace drive shaft center support and bearing, renew trans and motor mounts. try a flex disc -- reinstall old one. problem still exists -- suspect problem in trans or torque converter."

In the parts list the charged me for 2 seals, center support, bearing, trans mount and 2 engine mounts. They told me that the engine mounts did need replacing and so did the trans mount.

I am about to take it to the dealership and let them give it a try (I'll tell them what it isn't as above and see if they can find what it is) -- but I wanted to see if anyone here has any ideas what it could be.

I have searched the forum and have not found a similar situation.

As always, I would appreciate your input.