Hi Doc
"around 2,000 rpm it makes a terrible noise and causes a shuddering effect which can be felt through the whole car" ok guys were not talking about an instrumentation glitch. Sorry Doc - a play on a movie line involving 3 guys with a problem and the people to solve it were a lonnnnnnng way away.
What I'd do Doc is put her up on some stands and get under there and start looking for anything out of place. We don't want to make anything worse than it already is.
First - as others said look at the engine mounts. I remember your post from a few days ago when you mentioned that a bolt had done a runner on you. Another one could have bailed and the those left could have broken, or worked loose.
Second - as others said tranny mounts. Back end of the tranny would let the front of the driveshaft move around and that'll give you a real bad feeling through the seat. It'd be real bad if you're doing more road work and you get to find out if your new shaft loop really works.
Third - check the driveshaft for anything loose/broken. Could have blown a bearing in a joint or tweaked a pin in there. Try to turn the shaft by hand with it in neutral and the parking brake on, or any way of stopping the rear wheels from turning.
Fourth - check the rear end for any broken bolts etc. Above 2K would be getting to a speed where any slight out of balance in the rear end, wheels and tires would start to show up if anything is loose in the rearend. Check to see that everything appears to work as it should.
Fifth - turn a rear wheel and feel for any tight or firm spots. Listen for any scrapes, clunks etc.
Sixth - do the same to the front.
IF that finds nothing then we've ruled out all the mounts that hold the drivetrain to the car, probably the driveshaft and everything behind that.
The brake lights coming on when this vibration happens made me think that a pad could have come loose, or the pad material could have seperated from the plate. I think that spinning each wheel would show this up.
If nothing shows up by the above then it's a problem that involves dropping the tranny and shaft out. Clutch would be high on my list as it is with the other guys. With the shaft out check that it hasn't thrown any balance weight(s) it may have/ have had.
I'm leaning to something in the brakes as when it happens the system is getting pressurized to trip the lights to come on. I can't really see anything in the clutch side doing that - but with cars about anything is possible .....
I remember many years ago spending a long time checking out the rearend suspension on a car to cure the squeak. Greased everything, checked all the bushes etc, checked the brake drums (it was a while ago) .... still squeaked. Went away when I took the stone out that was jammed between the spring and the shock.
