I've got this horrible rattle at 1800-2000rpm when cruising. Sounds like it is coming from the transmission. I did have a converter installed several months ago and I can't remember if it started before or after that. It's very annoying. Any thoughts?

 

You still running cats? could be a bad cat.

 

You say you had a TC installed reciently... In that case i'd probably start and check the bolts between the flexplate and your torque converter. One or more bolts might have started to come loose and causing the rattle. Atleast its a easy spot to start...

 

cats are brand new Dynatechs.

 

ok, anyone have a pic of where these bolts are? i'm not exactly sure what i'm looking for.

 

You should have a inspection plate about 2 inches in diameter on the bottom of the bellhousing. Cant say i have any pic's to assist. But once removed the Flexplate and front of the TC is clearly visable. Hopefully someone else can give a better description than i can

 

It could be a cracked flexplate. My older truck sounded like it had some empty cans dragging under it when I drove. The bolt holes that attach the flexplate to the crank had spider cracks between half of them. It would not have been visible through the inspection plate... only with the transmission out of the way.