I'm looking at a '96 Aerostar AWD with 109,000 miles. The seller says that the right from wheel will "chatter", or act like it's on a washboard road, and that a "clunky sound" came from it. He says that it's only happened a couple of times at highway speed, and that it's intermittent. He's taken it to a shop, and they couldn't find anything wrong, but it's happened since then. They only want $800 for the van, so if the repair isn't too expensive I might be interested.
Any ideas on the problem? Thanks!

 

I've never heard of a front wheel chatter but it sounds a lot like the rear wheel clunk that is somewhat common on AWD Aerostar's (I've had it on 1 out of 3 AWD vans) What the rear wheel clunk is the AWD system locking one of the rear wheels causing the wheel to skip or "clunk" it most often happens when doing a sharp turn at low speeds. That problem is tried to the speed sensors on the transfer case but I'm not sure what exactly the fix is, in my case I drove the van for years with the problem and after the transfer case broke (I think a unrelated problem) I replaced it and it hasn't happened since.

If you can duplicate the problem (try low speed tight turns) you can see if it is the AWD system by unplugging the AWD computer under the drivers seat, if the problem stops its the AWD system. You can run the van safely without the AWD system plugged in, you'll still have AWD it just wont try to move power around if it detects slip.

 

Thanks for the reply. They said that it's only happened at freeway speed, and that it's very intermittent.

 

Rosett, your symptoms sound like a front wheel bearing is failing. It may also be the CV joint. I found a problem on mine by chance when I was replacing a failed CV boot. I found that its retainer ring had broken, so I was able to pull the inner shaft out. I found the ring in 3 pieces inside the CV joint when I was cleaning out its old grease. I don't know how long those pieces were moving around the ball bearings, but it would have caused major damage.

SKaero, the problems you're describing are caused by either a failing speed sensor or front and rear tires that are too unevenly worn. The 4wd computer is fooled into thinking that the wheels are slipping, so it tries to lock the front driveshaft to the rear. Around tight turns, this causes severe binding, and is only alleviated when the Morse chain in the transfer case skips. And yes, eventually this damages the TC. Or, you can do as you suggest, and unplug the 4wd controller.