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

Tiny
NIHAL
  • MEMBER
  • 2005 BMW X5
  • 3.0L
  • 6 CYL
  • TURBO
  • 4WD
  • AUTOMATIC
  • 80,000 MILES
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.
Thursday, January 23rd, 2025 AT 2:51 PM

3 Replies

Tiny
STEVE W.
  • MECHANIC
  • 13,828 POSTS
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.
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Friday, January 24th, 2025 AT 1:05 AM
Tiny
NIHAL
  • MEMBER
  • 15 POSTS
Okay, I will look more into it. Thank you.
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Saturday, January 25th, 2025 AT 5:20 PM
Tiny
STEVE W.
  • MECHANIC
  • 13,828 POSTS
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.
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Saturday, January 25th, 2025 AT 6:47 PM

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