My '94 Suburban 1500 is having a problem. On acceleration in second gear, right before it shifts, I'm getting a metallic rattling wobbling chain-like sound. If I shift into second gear the noise is constant once I reach about 2000 rpms. I got under the truck and I'm not seeing anything. The sound "seams" like it's coming from the lower dash area, maybe to the passenger side of the transmission. That's where the catalytic converter is located.

If I drive normally in overdrive, I don't have a problem. The sound only comes under load and rpms above 2000, and when in overdrive I can recreate the noise only by jumping on the accelerator and forcing a downshift. While in third, same thing, but in second I can recreate the noise with any reasonable acceleration.

I'm assuming it's my transmission due to the relation to shifting and rpms, but could it be the catalytic converter? Anything else it might be?

 

I don't think it is the cat. Sounds more like the second gear has a problem. Take it to a tranny shop and get a free checkup.