I have a 2003 Ford Escape with AWD. One tire has been damaged and is not repairable. The other tires are 1 year (~10k) miles old. Without looking at the car, the tire shop told me that I must absolutely replace all four tires.
I’m looking for some actual information based on the facts of this particular AWD system, not opinion, lore, or a desire to make 4 tires’ worth of profit off of me.
From what I understand, this is an “on-demand” system. It’s basically a FWD vehicle with a center differential that allows the rear wheels to be engaged as necessary. On the dash there is a “4x4” selector switch. The setting for this switch is either “AUTO” or “ON.” Does anyone actually know how this system works?
The electronic selector switch leads me to believe that the rear wheel engagement is managed with some sort of physical actuation, not some a limited-slip coupling. If so, how does the vehicle detect front wheel slip? I would imagine it would use the front wheel speed sensors like are used for the ABS, but I’m just speculating. Since it’s an open differential right-to-left, I would think that the front right and left wheel speeds would be compared to determine if the front wheels were slipping, not comparing them to the back wheels.
The owner’s manual does not specifically address this. It just mentions something generic about making sure that all four tires are the same size. It does not address it as an issue with the AWD system. Also, “same” is not defined. Clearly there has to be some tolerance for differences tire wear, right?
Incidentally, when I asked the tire shop to explain my AWD system and why I needed to replace my tires, they told me my vehicle was “like a Subaru.” That didn’t inspire me with confidence.
Thanks for any input,