vibrations and grinding sounds -- motormounts or something else?

[silvah_gsx]

Driving home from school today I noticed a vibration through the shifter, the pedals, and the floorboard (odd combination). There's also a grinding sound on decceleration, like a rock shaking in a muffled tupperware container, and sometimes also when idling. Its also idling at about 800-850, even with the engine warm (may or may not be related).

I thought this would be motormounts gone to hell, but I shook the engine by the cam gear cover and it only moved an inch or so fore and aft.

Any ideas would be great, thanks in advance for your help .

Ari

PS
Mods sorry if this is the wrong section, dunno where else a motormount question would go though.

 

[Auto RS T]

You can visually inspect the motor mounts to see if there are torn.

Shaking the motor by hand isn't going to give the same amount of torque the motor puts down. Have someone rev the motor up while you watch from a safe spot outside. You don't have to rev it to the stratusphere, just enough to watch the motor move.

 

[silvah_gsx]

I had my friend rev the engine while I watched, and it moved fore/aft maybe 2 - 2.5 inches, and moves fore/aft up to an inch when idling. Does that seem normal to you?

Also if it is motormounts, would that explain the grinding sounds under deccleration?

Thanks in advance.

 

[Auto RS T]

Judjing the movement is going to be up to you. That movement doesn't sound like anything crazy for metal to be rubbing on metal.

Did it make the noise when you revved it up?

When it is idling what part of the car does the noise come from?

Check for loose exhaust. I don't really understand the grinding. Hard to diagnose a noise.

Possibly you could better describe the noises and what part of the car they came from.

 

[fourreGsixty3]

How long ago did you check the harmonic balancer? I would check that because while driving it can seperate, or crack, and cause vibrations...the thing it trys to prevent.

Dustin

 

[silvah_gsx]

Did it make the noise when you revved it up?

No, it sounds fine when revving. I dont think its the engine anymore, because I took it around the block and it grinds regardless of engine RPM, but I can only hear it when deccelerating and coasting.

what part of the car does the noise come from?

It sounds like its coming from the clutch/tranny area, behind the engine but ahead of the shifter, and down in the tunnell where all the linkages go.

As soon as I can get to a lift I'll check the cat I just installed.

To clarify the sound, I guess it sounds like a low-pitch muffled gear grinding. Hope that makes it easier.

 

[Auto RS T]

Check your new exhaust clearance. It could be rubbing on the body, or driveshaft.

 

[92awddsm]

Also check the fluid level in the transfer case.

 

[silvah_gsx]

Thanks for all the suggestions guys. I won't be able to get my car up till Monday (Autoshop at school) but I'll get back to you with what I find.

Ari

 

[silvah_gsx]

Okay well today I got the car up and checked the cat for rubbing. Tightened one loose bolt there but it was never rubbing on the driveshaft. I checked what I thought was the transfer case, but I'm looking in Chilton's now and it was the gearbox

I'll be changing the fluids soon, hopefully that'll make some difference. The car drives fine now though, so maybe it was a temporary thing. Thanks again for all the help