I dont own a Monte Carlo, I actually own a Grand Prix GTP. But I was referred here by another user due to my situation.

A few months ago I found part of a roll pin in my transmission pan. Ended up narrowing it down to the pin in the differential. After finding a HD differential, I went and did the swap this past Saturday. Went half a mile and realized it was making a loud noise. So i pulled it back apart again to find the teeth on the planet gears on the Differential to be all nicked up. Thats when i realized that my 'new' diff was a little different. So i made sure everything was clean, installed my old one with the new ones roll pin. Took it for a drive and got the same result... Pulled it apart a 3rd time and basically ended finding the thrust bearing behind the parking gear shredded to pieces.
So I cleaned all the shavings out once again.
Bought a new thrust bearing locally.
Installed the thrust bearing with the tranny grease to make sure it set correctly
Cleaned up the teeth on my original differential.
Installed it all and when i went to put the diff cover on it would not sit flush. I did notice this before figured it was normal. But its not. So i ended up tapping in the output shaft, thinking maybe its not set?. This seemed to set everything right! Cleaned up and took it for a ride. Still doing the loud noise..
The sun gear is facing the correct way.
I dont understand.
The ring gear does have a very very tiny mark on the one tooth but its not going to cause it to go to shred like this.

Please help

Thank you!!

 

I honestly dont think there are any transmission guys around here.. Id think youd maybe have more luck at the GP forums.

Good luck with your issue but to me personally, thats a whole different language.. XD

 

I honestly already did post over there. But they stopped responding..

Youre telling me man. All because i found a 1/4 in piece of roll pin in my pan and wanted to be 'preventative'..

Thanks again