I have a bad rear differential (one of the driveshaft seals is shot, and almost all the oil is gone), and I was wondering if this can affect my automatic ZF-6HP26 transmission.

  • 2
    No it cannot, you better fix that seal before you trash the rear differential.
    – Moab
    May 25, 2018 at 12:48
  • @Moab, It's already very noisy, I guess I'll need another one soon. It's good to know that the transmission is safe, since It was completely rebuild a couple of months ago. May 25, 2018 at 12:51

1 Answer 1


As Moab states in the comments, a bad rear differential cannot hurt an automatic transmission. The only thing attaching them is a driveshaft. Other than that, they are completely independent assemblies.

Even if you've already done irreparable damage to the rear end, you can most likely prolong its life by topping off the gear oil and fixing the seal. Even if it is noisy, you might find getting these two things done will quiet it down and keep it going until you can plan on fixing it, either through a rebuild or replacement (if it's needed at all).

  • I was thinking of this scenario: Some of the gears, or bearings, inside the diff unit fails (let's say it disintegrates) causing the input driveshaft to lock in place. Is this possible? How would the transmission handle this? May 25, 2018 at 13:08
  • 1
    The way a differential fails is usually (as in your case) you lose all of the gear oil, the bearings will heat up. If they heat to the point of seizing, this causes undue pressure on the ring/pinion. The ring/pinion then fail. The driveshaft will go around, but the car won't go anywhere. Plenty of nasty noises ensue, but still no damage to the transmission. Especially in an automatic transmission, the torque converter will take up all of the slack which might cause any issues with the transmission. As long as the transmission is in good working order, your diff will go well before it will. May 25, 2018 at 13:13

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