harry604

i replaced my motor mounts to oem ones and now the flanges on the cats and mid pipe rattle on the tunnel plate when accelerating hard...

do the trans mounts actually go bad like the motor mounts? also getting vibration in the shifter when accelerating hard

2006 stock zo6 100k miles

subfloor@centurytrans

It's a common problem and this has worked for me on a few Z06s:

- loosen the exhaust bolts at the head(s)
- wedge a small prybar or thick screwdriver in between the tunnel plate and exhaust flanges
- retighten the exhaust bolts again at the heads
- pop out the screwdriver

You may need to do it again if you don't introduce enough clearance the first time.

harry604

i tried that i might have to make a bigger gap i guess….
did you loosen the mufflers to the mid pipe too ?

subfloor@centurytrans

No, just the manifold bolts.

harry604

i tried but does not seem to do anything.... ill try again maybe ill loosen the whole exhaust..

this became a problem after i installed new oem motor mounts

harry604

ok fixed it did 1 side at a time gap looked the same but no more rattling….

can the trans mounts go bad ? there solid mount no fluid….

Apocolipse

The replacement oem ones seem to be a little higher since they are made for the weight of the LS9

harry604

but can the stock oem trans mounts go bad ?

pdc001

Did you loosen the entire exhaust to fix it or just only loosen the exhaust manifold on both sides? I need to fix this rattle as well. It's driving me nuts.

harry604

manifold bolts, then put prybar between flange and tunnel plate…. only did one side at a time… previous times i did both at same time and it never worked

Apocolipse

Prybar needs to be in there when the H pipe bolts are loose - that meet up to the catted section - not the bolts on the head.

And as with anything rubber the trans mount can go bad but that’s most likely not your issue here

tommyc6z06

I had this same thing after my head swap (manifolds off of course)...the flanges touched the tunnel plate.
I used my angle grinder to trim the flanges a little...