I have a 93' Z28 Lt1 (4l60 trans)

So anywho, when I put my car into drive and hold my foot on the brake (this is the only way to make the sound) ill give it a little gas to where the tires wont spin maybe 900 rpm. It makes a little knocking sound. Doesnt do it at any other time but only when my car is in drive and gas at a very low rpm it goes away after approx. 1100 rpm. i wont hear it anymore.
and thats everytime hot or cold.
any ideas?

and sorry if this is wrong place wasnt to sure where to put it.

 

I have a 96 z28 with a automatic trans. Mine does the same thing. Sometimes it will even knock when I'm driving anywhere from 20 to 50 and let off the gas and press it again it will knock. Someone I know said it's possible it could just be a u u joint but I haven't really checked into it a whole lot

 

Someone told me about the u-joint problem. I looked into it and was certain that wasnt the problem. Anyway i took a closer look popped the hood and everything, and it almost sounded like that sound was coming from in the valve covers. But I don't believe it to be any kind of internal thing.

 

hmm...well if you find anything out i would appreciate if you would let me know..like i said my problem sounds exactly like yours..and if i find out what the problem is to ill let you know

 

Well I looked a little closer at it today. It almost sounds like somethings rattling around from underneath the engine. I know its not internally (no bent rods or anything). Its more of a rattle sound and still only at a low rpm in gear.

 

maybe loose torque converter bolts.

 

Yea...well I'll take a look at it tomorrow. Now there's a loose wobbling sound coming from the front end while driving. I don't know if this sound is connected to the loud noise switching gears or not

 

I have the same sound on my 6 speed. I'll hear it from time to time. Sounds similar to cracking a knuckle.

 

I figured out the problem steve. It is actually my tensioner pully making the sound. Its loud and almost sounds like its coming from underneath the engine, but it was really the tensioner the whole time. Just thought I should share some insight with you. Check for yourself, grab a friend to help you, but make your car make that noise, and when your doing it have someone look at your belt as you let off the gas. You should see the belt wobble a little bit like its losing tension. If the belt doesnt then look into your u joints like you said before