My wife has a Bronco II X with manually locking...

Dear Car Talk

Dear Car Talk | Nov 01, 1994

Dear Tom and Ray:

My wife has a 1987 Bronco II 4X4 with manually locking hubs. I say it's all right to leave the hubs locked, even though the four wheel drive is not engaged. This is for short drives of less than 20 miles. It's a real pain to have to get out of the vehicle and unlock the hubs. What's your advice?

RAY: I know what the real issue is, Bob. When it's 13 degrees out, she wants YOU to get out and unlock the hubs, right? But because you were thoughtful enough to include a $20 bill with your letter, we'll give you the justification you need for staying the in the warm car.

TOM: It IS OK to leave the hubs locked when you're not in four wheel drive. The only real drawback is that you'll get poorer gas mileage.

RAY: When you're in four wheel drive and the hubs are locked, the transmission turns the front drive shaft, which in turn, moves the front wheels. When you're OUT of four wheel drive and the hubs are locked, the wheels are still attached to the drive shaft, but the drive shaft isn't attached to the transmission. So, in effect, the front wheels are sucking up energy because they have to turn the front drive shaft (and overcome that friction) even though the drive shaft isn't attached to anything. That's why it's a waste of gas.

TOM: And sure, those parts do get a tiny bit more wear and tear when you leave the hubs locked. But if your wife wants us to expand on that point, she'll have to send us 20 bucks, too.

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