Car Talk: Center differential makes the difference in towing | Lifestyles

Dear Car Talk:

I just read your recent answer to David, about how to tow vehicles with automatic transmissions.

It made me think about my parents’ RV trips years ago, where they towed a ‘95 Jeep Cherokee with an automatic transmission behind the RV. The transfer case was in Neutral while being towed, and I don’t remember about the transmission itself.

Was that acceptable or was that causing wear or damage to the drivetrain?

Thank you. — Stuart

Well, since they got away with it, I’m going to conclude that it wasn’t that bad, Stuart. After all, you didn’t describe it as “a ‘95 Jeep Cherokee that went through three automatic transmissions.”

In 1995, the Jeep Cherokee was an old-style four-wheel-drive vehicle. That means it did not have a center differential. Modern all-wheel-drive vehicles have center differentials, with all four wheels connected to the power train all the time. For those vehicles, we recommend flat-bed towing exclusively.

But on the old Cherokee, by putting the transfer case in Neutral, you could literally disconnect the front drive shaft (and front wheels) from the rest of the drive train. That way, the front wheels could turn freely without being connected to the transmission.

So, if your folks put the transfer case in Neutral and lifted the rear wheels of the Cherokee off the ground, and towed it (facing backward) with its front wheels on the ground, that would have been perfectly safe.

If they towed it on all four wheels behind their RV, even with the transmission in Neutral, then the rear driveshaft would have been turning the components of the automatic transmission.

And while it wouldn’t necessarily ruin the transmission, it would cause the transmission to heat up. The transmission only gets cooled when the engine is running, so towing it — especially if it was at highway speed for hours at a time — certainly could have shortened the transmission’s life.

How could you know for sure? You’d have to track down the person your parents sold the car to and ask them. But I would definitely conceal your number when you call, just in case they’re still steamed about it.

— Got a question about cars? Write to Ray in care of King Features, 628 Virginia Drive, Orlando, FL 32803, or email by visiting the Car Talk website at www.cartalk.com.

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