Knocking sound at the differential and gear housing that intensifies with increasing speed

Thank you for replying to my car question.

I did stand the vehicle on jack-stand and had it run on fifth gear over the week-end and the following are the latest findings
1. The knocking from the differential vanishes - it only appears when the wheels are on the ground (bearing the weight of the vehicle) and driving above 20km/h
2. Left wheel spins slow as I mentioned in my initial question but something else surfaced - the left axle bearing must have been damaged. It sounded similar to a damaged wheel bear and I could feel the vibrations.

I am going to check on that axle and its bearing and replace the bearings (LHS and RHS.) Do a test drive to see if the knocking sound still exist before I will proceed to attempt on the differential work.

I will see if I can record a video of the knocking sound and post later.

I did had a look at the links after posting my initial question but thanks all the same for your help. Will keep you updated as I continue on this diagnosis and repair so others facing similar issues can use the information.

Willie Mondo

Okay, I realize my mistake in my reply to the first answer.

I did a manual check on both wheels by hand (engine off and gears in neutral) and found the left wheel was sort of stuck and produced noticeable play. Clear grinding sound coming from the wheel side and tiny but audible clanking sound from the differential housing. I am pretty sure the axle bearing is damaged.

The wheels are supposed to be spinning smoothly and without much play or grinding noise if spun by hand. Therefore I will check on the axle bearing first this weekend, then proceed to the differential. I have done wheel bearing before so I will be okay with that.

Thank you.
Just a clarification - this is a rear drive axle issue so information from this link (https://www.2carpros.com/articles/rear-axle-seal-replacement) would be handy in my case.