So when I really get on my car I hear this horrible grinding noise. Almost like a really bad water pump/chipped gear sound that's grinding it's self. It does not seem to do it in 1st or 2nd. but in 3rd as it's working it's way up the rpms it seems to make this grinding chatter sound. I need to replace my flexplate as it is a bit wobbly but if it was that it would do it even when revving the engine up at idle . Im replacing my flexplate this week. I also do have a spare th400 and 3000 stall conveter. Im not a trans nut so any input will be appreciated.

 

Check your starter housing or teeth on the starter drive with a wobbly flexplate. I ground off about 1/8" on my IMC,s drive before I knew it! Just an option.

 

It is hitting. I added a washer to stabalize it and it helped but still wobblin. I'm pulling the trans to do the flex plate . What has me baffled is the fact. It does not seem to do it if I old 1st gear. Seems like it's doing it in 3rd when it's pulling hard. I guess I'll do one thing at a time and go from there.

 

I'd put the spare T400 in when you do your flex plate, and tear this one down. Just my opinion Copper.

 

That will probably be a good call.

 

I'm droping the pan tonight. Last time I had it down. I saw some big flakes. I was planning on. Swapping from my current th400 to a 350 which at this time I have decided to do so. I'm trading my th400 for a th350.

 

You'll need a different driveshaft going to the T350, the xmember will need to be moved forward and the ebrake will need to modified and you'll need a kickdown cable at the carb. Do you really want to do all that?

 

I already have the driveshaft as I planned on it. I manually downshift most of the tme my th400 has no kick down solenoid. I actually have to put in the ebrake stil I'm changing it to hand lever.

 

Alright. I dropped the pan tonight. it has bee less than 3k miles since I dropped it. I found flakes and sediment last time and I found more metallic flakes and sediment this time. I think I might have a clutch pack that's going one of the metallic flakes I picked up seemed to have that paper coating the clutches have, but I don't know enough to diagnose, what I do know is something is going bad inside since last time I cleaned the pan off really good. Could that be the reason for the metallic grinding noise im hearing in 3rd gear under heavy load w.o.t at higher rpms . needless to say it's coming out.