Nasty vibration
 

Well, I'm bringing this in soon to get looked at, but I wanted to see if anyone had any ideas to what this could be.

Recently, I started to get a really bad vibration. It only seems to happen at idle, and when it's just off idle. I hit right around 700-750 rpm. It's a low frequency, almost lumping sound, like something large hitting the car from underneath. I recently got my clutch and FW done and I put in an Efini y and crossover pipe. I checked to see if anything seemed loose, but I couldn't find anything. I noticed that it seemed louder from under the car than from under the hood.

Acceleration seems fine. Idle is stable. Vacuum and boost are perfect. I also did notice that the top rear nut was loose on the DP, but that had been like that for some time I think as I found this a week before the vibration started. I tightened the nut as best I could so I really don' t think that's the issue.

Back to the clutch thing, I felt what was kinda like what's happening now, but only when in 1st, and engaging the clutch. It went away after a while and just attributed it to break in. It almost feels like that now. I think some of you with the same upgrade might know what I'm talking about.

So, there you have it. Thanks in advance....

Christian

How are your motor mounts?

If you're at idle, then jam on the gas to the floor, does it thump/vibrate the loudest?

Heh...well, I haven't gotten to look at the motor mounts yet. I thought about that, but buried that in the back of my mind. If I don't think about it, that's not the problem. :D Seriously I will look at that. On a counterpoint, wouldn't I notice extra movement of the motor when I blip the throttle? Course, I have to do that to check...but it's something to keep in mind.

Cavellm...no. Only at idle. When I accel, I don't hear/feel it.

i think maybe it's your torque brace. You might want to remove it and see if it goes away.

I know it's not that. I know exactly what that sounds like when it's FUBARed. It's not that. I took measures to dampen that up some. But thanks. :D

its your motor mounts, I fear.

Woohoo for not being the motor mounts. I've pinned it to a section of the exhaust smacking a crossmember. I don't know if that hanger has just lost it's supporting ability or what. Anyway, while I was down there, I came across this. This brace is located about 4" or so forward of the catback/cat link and tied to both sides of the car. On the forward edge of this are two flange like pieces that looks like something was ripped off of it. Forward of that just about where the driveshaft hooks to the tranny is another crossmember that has a couple of bolt holes with nothing in them. I've never been a body guy, so I have no idea what this is for. I've tried looking for underbody pics, but came across nothing. I know that aftermarket PPFs supposedly tie the diff to the tranny, like the F-body torque braces, but I have no idea what the stock one looks like, or if I was even looking at the right thing. More help would be appreciated.

Thanks in advance again.