I bought a 2012 Liberty about a month ago, it has 100,000 mi on it and when I test drove it I noticed a very slight knocking noise but didn't think much of it until I started driving it home. I've taken it to three different mechanics, the first one told me my engine was blown and it was a rod knock, the second one told me it was my starter, and the third told me it was a wheel bearing.... I replaced the starter just to be sure and it did not fix it, didn't have high hopes for that anyways.

The symptoms are, while the engine is under load there's a knocking noise that sounds very similar to a rod knock. The speed of the knock correlates with the engine speed. It is heard most clearly in the cabin. At idle there is no noise (except for a moment when the AC compressor kicks on) and above 3000 RPMs there is no noise, that or the knocking is happening so fast it blends into the background. It is heard loudest if you sit in the cabin with a door closed, in drive or reverse with your foot on the brake and holding the RPMs at 1000. You can also hear it accelerating from a stop but once the RPMs are above 2000 you can no longer hear it. I cut open my oil filter and there are no metal shavings, I drove it a thousand miles from Las Vegas to Texas and the noise has not changed at all or gotten any louder. It's hard to tell because there's so much other noises underneath the Jeep but it sounds like it's coming from the rear of the engine or front of the transmission. There are no drivability issues whatsoever I have used a stethoscope to listen to all the bearings and it's very difficult to pin down where exactly the noise is coming from but all of the bearings sound fine. I'm really leaning towards the flex plate however when I took off the inspection panel there was not any signs of wear or damage. I could only get to the bolts that connect from the flex plate to the torque converter but I'm not able to see the bolts that connect to the crankshaft. Two of the shops were specific transmission shops but I have a feeling that neither of them actually heard the sound even though I showed both of them. To be fair if you don't know what you're listening for or how to reproduce the sound it is hard to recognize. I have heard videos of what a cracked flexplate sounds like and it sounds very similar to that but in the video it was happening at idle and was way louder. I believe there's probably a hairline crack around the bolt holes that connect to the crankshaft but the only way to confirm that would be to drop the transmission which is a very big job based on a hunch. Anyways I was hoping somebody with mechanical knowledge could chime in. I'm not a mechanic, but I do know how to do some things. If anybody has any ideas of what that knocking could be if not the flex plate then I would appreciate any input.

Thanks,
Michael