Rattling gears in 2002 Nissan Pathfinder

Hi all, I recently had the the entire clutch and pressure plate replaced in my car and ever since there has been a sound like metal rattling in gears 2-4. It happens when I have low revs in those gears (particularly going up hills) and seems to go away when I am at high revs (~3k+). The mechanic I initially used says it’s nothing but it sounds awful and is making me very nervous. The “Check Engine Soon” light has gone on as well.

Any help or advice would be greatly appreciated!

Although it is a distinct possibility, you have to leave open the possibility that the rattling isn’t from the transmission/clutch. You need to get the error codes read from the computer - many big box auto parts stores do it for free. Write down the exact codes in the format “P0123” and post them.

For now, I would also suggest having someone who DIDN’T do the clutch take it for a drive and a listen.