727 rattling noise

[phantom]

Hi,
another 727 question. When i put it in Drive or second gear, i get a rattling noise from under the car. Just like the exhaust hitting the floor at a certain rpm. The funny thing is, this does not happen in reverse, park og neutral. And its only when idling. As soon as i touch the pedal to rev the engine a little bit, the sound disappears. I dont think its the exhaust, because i cant find anywhere its touching the floor, and the sound would also be there i reverse to, dont you think?

[cdr]

loose converter bolts, or cracked flex plate.

[phantom]

If its the flexplate, wouldnt it make the noise even in neutral, reverse or park too? The converter bolts are checked and are tight.

I googled some, and found a website, PATC. There, a guy explaines different sounds, and he uses a 4L60-E trans as an example. I dont know if the 727 and 4L60-E works in the same way, but he adresses the noise i have on mine. This is what he wrote:

"Torque converter noises are easy to isolate. Since the entire converter (pump, turbine and stator) turns while the transmission is in park and neutral, a converter noise will go away in those ranges. When the transmission is in gear and the drive wheels are stationary, the turbine in the torque converter doesn't spin, because the turbine shaft is stationary. This is when the bearing between the turbine and main housing of the converter is working. If the noise is there only in gear with the drive wheels stationary and goes away in neutral, suspect the torque converter."

I dont know the condition of my converter, or how old it is, it came with the trans. Going to swap it out this winter with the trans overhauled at the same time.

[cdr]

.

[c00nhunterjoe]

Sounds like a cracked flexplate or the exhaust is hitting.

[John_Kunkel]

In Park and Neutral there is little load on the converter so it spins with little resistance, in Drive or any forward gear the lopping of the cam might account for the rattle, in Reverse the line pressure is increased dramatically which puts more load on the converter.

This could explain the variance of the noise from a broken flex plate or loose converter bolts. Again, just spitballin'.