When I attempted to accelerate, I heard a loud knocking sound?

2005 BMW X5
80,000 MILES • 3.0L • 6 CYL • TURBO • 4WD • AUTOMATIC
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NIHAL
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I bought my car used and it was running good, and I had lost the key. I bought a new key after a few months, and I took it for a drive. A few minutes into the drive the car stopped moving as I was giving gas, and I heard a loud knocking sound. I stopped on the side of the road and put it in park, and the transmission wouldn’t shift into drive. When I tried to shift ther transmission in drive, the car wouldn’t start making the knocking noise. I found that the noise was coming from the rear differentials. I think the bearings and bushings might be broken. Is there a way to drive the car without the rear end? Please let me know and also please let me know what could be wrong. Thank you.
Jan 23, 2025 at 2:51 PM
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STEVE W.
  • ✓ASE Certified Mechanic
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If it's the rear differential, no it cannot be driven without it. It could be the differential gears or the ring and pinion or a failed U-Joint. You would need to get it up on stands and go under it to see what is causing the noise as there are multiple items. From there you can plan out a repair.
Jan 24, 2025 at 1:05 AM
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NIHAL
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Okay, I will look more into it. thank you.
Jan 25, 2025 at 5:20 PM
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STEVE W.
  • ✓ASE Certified Mechanic
  • 15,200 POSTS
  • ASE Certified Mechanic
With it in the air you can rotate the tires and drive shaft and see what makes noise. Hopefully it's just a bad U-Joint.
Jan 25, 2025 at 6:47 PM
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