I have '90 vert with an automatic transmission. It recently developed a rattle
underneath the engine that only manifests itself at low idle when I shift to drive or
reverse. It also rattles continuously when the A/C is on . I verified that the exhaust manifold heat shield is tight and eliminated all exhaust system possibilities. I've put the vehicle on stands and listened with the engine running and A/C on - sounds like the rattle is coming from the drive plate/torque converter
area. I've replaced the starter thinking the starter gear was hanging up on the
drive plate but the rattle remains. Any help would be much appreciated.

 

Mostly likley the heat shield that covers the exhaust manifold next to the engine is loose. One of the bolt holes in the thin metal shield tends to corrode and separate / rip over time. With the shield only held on by 1-2 bolts, it tends to rattle at certain RPMs/frequencies. You can make another heat shield out of roof flashing (metal strips), buy a new one, or see if a mazda salvage yard has any good ones.

If the bolt hole in the shield is mostly there, you can "getto rig" it and use a larger washer to help clamp it down. Better yet, remove the shield and take it to a machine shop / auto restore place and have them weld the washer or new metal onto the shield permanently.

 

my rattling noise was caused by the air pump tube... isnt that a weird one

 

Its trying to tell you to do a 5 speed swap

 

heat shield is tight .....noise is definitely coming from the drive plate/torque converter area

 

I have a car doing the exact same thing. Did you or anyone find the cause and a solution. Rattling sound at low rpms that goes away as rpms build?

 

i have the same [roblem and i was thinking the engine mounts..cause mine r worth ****

 

could be engine mounts, transmission mounts or if you are sure it is coming from the bellhousing it is possible you have a cracked flex plate.

be sure all the torque converter bolts are tight before assuming it is the flex plate though.

 

I got under the car and removed the lower inspection plate on the bell housing and it definately has a cracked flex/drive plate.

Next question is, is there most likely any other damage to the engine, torque converter, or transmission that may not be as easily visible?

I know that I will have to remove the transmission to get the flex plate off. Is there anything particularly difficult about this or is the flex plate just bolted to the engine?

I will also be posting in the classified section for a flex plate so if anyone reads this first and you have one shoot me a pm with a price plus shipping to zip 37659.

thanks in advance!!

 

it should be pretty straight forward, 3 bolts to hold the torque converter in place and 6 bolts holding the flex plate to the counterweight if i remember correct. nothing else i can think of to check while in there, flex plate cracking is fairly common on many vehicles, in that i would suggest picking up a new felx plate if possible to prevent this from happening again in the near future.