Does AWD perform better on an automatic versus a manual transmission?

Dear Car Talk

Dear Car Talk | Oct 01, 2000

Dear Tom and Ray:

I've been leasing Subaru Legacy wagons for the past five years. My lease is up this month, and I intend to lease yet another Legacy wagon. However, I'm getting older, and I am considering an automatic transmission instead of my usual manual. I'm somewhat concerned, however, about mixing all-wheel drive with an automatic transmission. I recently read that while Subaru manual transmissions divide the power equally among all four wheels, automatics are split 90-10 front and back, with some fancy-schmancy, highly sensitive, computerized gizmo that distributes the power according to need. Are you aware of any differences in roadworthiness of AWD Legacies with automatics vs. manuals? Is one safer than the other? Does one have better traction in snow, sleet or rain? I'm really getting sick and tired of changing gears every five seconds in stop-and-go traffic (my knees aren't up to it). Can I get the automatic? -- Jeffrey

RAY: Sure you can, Jeffrey. You're essentially correct about Subaru using two different all-wheel-drive (AWD) systems. But they're certainly both safe, and in our experience, they perform equally well in bad weather.

TOM: The manual-transmission Legacies use a purely mechanical, fluid-based AWD system. It distributes the power equally to the front and rear axles until one of the axles starts to spin. Then the fluid representing that axle heats up, gets thicker and directs more power to the wheels that are NOT slipping. It's a tried-and-true system, and it works well -- as you can attest.

RAY: On the automatic Legacies, Subaru uses a computer-controlled AWD system that normally sends most of the power to the front wheels. And when the computer detects slippage, it reroutes up to 50 percent of the power to the rear wheels to keep you going. And that system works well, too.

TOM: In fact, the system Subaru uses with the automatic Legacies is actually more sophisticated than the mechanical system you're used to. It shares a computer with the electronically controlled automatic transmission, and it can respond even more quickly to input from the wheels. So I wouldn't hesitate to go automatic.

RAY: Plus, with an automatic you can use that newly freed-up right hand to rub some Mentholatum Deep Heating Rub into your knees, Jeffrey.

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