Hello, my Jeep's been making a knocking grinding noise since I got it at idle. Noise isn't there when above 1500rpm, cold start it starts great about 30-45 seconds in it starts making the noise. once you drive a little bit and let it idle hot the noise is very faint sometimes or not there either. All flexplate bolts are tight. I seafoamed the truck and tried some different weight oil , didn't do any good. Oil pressure is great. 2001 xj automatic. Any insite would be great. Here's a link for video. https://youtu.be/eAl3H8S4A0Y