BMW 735i Grinding sound from transmission Inspection at your home or office.

Common reasons for this to happen:

• Transmission Fluid Is Low: You may hear a grinding, whining or growling sound if your transmission is low on fluid. It may also be a gurgling sound. It varies a great deal from one transmission to another.

• Transmission Fluid Is Contaminated: Your transmission fluid should be changed regularly to ensure that contaminants and debris are removed from the system. Over time, “fines” (small metal particulates) can build up in the fluid and cause damage.

• Differential Low on Fluid: If you have a rear-wheel drive setup, it might not be your transmission making the sound. It could be the rear differential. If you have an all-wheel drive vehicle it could be your center or front differential. All differentials require fluid to lubricate internal parts.

• Cracked or Chipped Gear: An automatic transmission producing a grinding sound may also have a chipped or cracked gear. If a final drive gear is chipped or cracked, you’ll hear a grinding or growling sound that stays consistent even with gear changes.

• Failed Synchronizer: If you have a manual transmission and you’re experiencing a grinding sound when trying to shift gears, the problem is likely to do with the synchronizers. These help you smoothly shift into each gear and when they go out, it feels like you’re trying to shift without using the clutch.