rangermonroe

98 GC 2wd sounds like there is a interference in there.

I sounds exactly like when the fan blade was hitting the transmission cooling like at a fitting. It is varies with RPM both in speed and intensity, tending to be less obvious at higher speeds.

My son seems to think that it is the flex plate, but I have never heard of one behaving like this. Dropping the tranny isn't something I want to do to check it's condition.

Any thoughts?

Gee oh Dee

Cracked flex plate or loose flex plate bolts.

rangermonroe

No kidding?

I have never heard of such a thing. Is this a common problem?

ETA: watched some videos on it, there are a bunch and that is how it sounds.

Thanks. Guess I know what I am doing this weekend.

Gee oh Dee

Check into it via the inspection cover, if they are just loose I think I've seen guys able to tighten then without much effort.

dave1123

Just to relate an incident that happened to a friend with a '72 Pontiac Firebird. He had this same noise with his car but it quieted when in gear and rattled in neutral. We dropped the inspection cover and found two of the converter bolts missing and the last one loose enough to egg-shape the hole in the flexplate. (GM only has 3) Messing around inside the cover, we found the other two. One laying in the bottom of the cover and the other on the ledge of the block near the rear main seal. All three were chewed up. We took the best one and installed it in a good hole until he could get two more. It amazed us that 300 hp was being delivered thru only one loose bolt!

I bought an '87 Chevy truck that had a new engine installed just before I bought it. After a couple of weeks, it started making a strange creaking sound when you gave it the gas. Eventually, the center of the flexplate ripped out and it stopped driving. On teardown, all the bellhousing bolts were loose which had caused the flexplate to crack.

Maybe one of these scenarios is the cause of your noise.