belair

I have an 86.5 that has a mind numbing rattling noise that is intermittent especially heard at idle. I thought it was coming from the cats but after dumping them with X-pipe install it is still there.
It seems to be coming from the flex plate area and the starter ring gear area.
The flex plate checks straight and I can feel no play in the starter gear. Any ideas? I would like to fix while it is still in the air.
Thanks

Bill Ball

It could be noise transmitted from bad torque tube bearings or loose RIVETS used around 86-7-8 to fasten the REAR flexplate to its center hub. I would expect that latter to be loud back at the torque converter housing. Of course, check that all the exhaust shielding is fastened down tightly and not rattling againt the headers or pipes. You should try a stethoscope or even a length of rubber hose against your ear to try to better locate the loudest point as the probable source area. Sometimes the noises transmit and are amplified elsewhere, like the bellhousing, so it can be tricky to track down the source. We had a noisy air pump that sounded loudest at the water pump area, but removing the air pump belt eliminated the noise.

GlenL

Start up the car get out and poke around. Use a mechanics stethoscope or cardboard tube to winnow down the locations. Hard to diagnose from the driver's seat.

I'll be optimistic and suggest it's a loose heat shield.

Lizard928

Verify that the front torque tube bearing has not migrated forward.
This is one of the first checks to make.

belair

It is still up on the jack stands for the X-pipe job, and the wooden broom listen test has it at the described location. Tommorow I will check out your suggestions and it does sound like a heat shield. Thanks so much

JHowell37

Check the air/smog pump. They make a lot of noise when they go.

belair

Smog pump deleted and running short belt for the fan.

belair

The noice is a metal to metal type noice that becomes more consistent as the car warms up. It seems to be isolated to the flywheel torque tube connection area. The flex plate is straight although the clamp has been welded. There seems to be some balance weights on the flywheel and corresponding notches in the bellhousing but no metal flakes. Could this be it? Heat shields seem intact.

GlenL

Is it in-time with engine RPMs or rattle?

Your lower bellhousing cover can be off while running the car to help analyze the situation.

belair

It may still be present but not heard at higher revs but is definitely a metal to metal sort of knashing noise. Thanks everybody! Car now runs well and looks good but sounds like it is coming apart.

belair

It definitely disappears at higher RPM, then returns when settling down to idle. Thanks again everyone.

Landseer

A couple thoughts.

Broken ceramic inside catalytic convertor.
Bolt, nut or metal of some sort in there.
Front antisway bar attaching bolt loose (BTDT)
Rotor shield contacting. Could be either side, front or back, and antennuate.

Some other discussion on here recently about loose caps inside cam chain tensioner, but it seems like the focus was earlier 32V's, ie 85.

The starter will probably rattle inside if you hit it with the heal of your hand. You will think thats the source, but probably it isn't.

belair

I thought it was the cats but they are now gone so are ruled out. On my way to check out other suggestions.

belair

My best listening with a stethoscope has me at torque tube. I can get sound along entire length. So looks like I got some reading to do.