btceng

I read your entire post and listened to the audio clip. I have a 98 4runner with a similar sound. Mine makes the noise loudest in reverse but has it in all gears. Several months ago I did a flush for a similar issue with the exception of a clunk going from park to drive. The flush and addition of Lucas additive fixed both the clunk and chatter. It's been about 6000 miles since and now it's back. The truck drives good but the noise seems like something that needs immediate attention. Thanks for the detailed description and thanks to others for the reference material. I think that I will pull the pan and check out the fluid for shards. The fluid was clean on the previous flush but I figured the fresh fluid had unstuck a solenoid or something. The fluid currently is clean and has no burnt odor.

Why is it most noticable in reverse?

BTW, 2wd and 215k miles. No major problems outside of routine maintenance. Owned since 2000.

tns1

The fact that your noises went away after just fluid changes says the problem is inside your trans, rather than being something like the flex plate.

I found that just looking at the old oil is not good enough. It is well worth dropping the pan to see how much metal paste is present. You can also pull, clean & check the solenoids, and clean the pan magnets. A trans flush will not get all of this.

My noises were most noticeable just after shifting from park to drive or rev.