Background: '93 Aerostar, 4.0 AWD, XLT Extended. Bought it this year with 103K miles on it, had lots of maintenance and tune up work done, plus all cooling system parts replaced. Now approaching 112K miles. Ran only synthetic oil in engine at first, now mix it up some (running dino oil now, likely back to synthetic next).

Recently, when cold, I hear a low thumping noise right around the cup holder area. It typically occurs after I've driven a short (mile or two) distance and come to a stop. Once warmed up, all seems well save for one item. When the van is warm, sometimes the 4WD light flashes 3-2. Often the 3-2 flash occurs at low speeds or at stop, then stops flashing at higher speeds. After reviewing many threads here, I thought it was possibly dirty sensors (the two on the transfer case), but the start of the thumping noise now makes me wonder. It just started a week or so ago, doesn't always do it, and we did have a cold spell around then (20's F). The fluid levels seem OK (I've checked them a few times, as have the last two mechanics who worked on it.)

I had the trans flush done when purchased. Planning to have the filter and fluid changed again (not sure they ever changed the filter or not!) and to use synth in there. So, are the thumping and 3-2 code connected? The 3-2 flash started before the thumping, but is happening more frequently now. TC getting ready to die, or could it be something easier? Thanks!

 

The thump could be that the front axle has litterally broken loose from the cradle. Semi-common problem with the Aero. Crawl under and visually inspect.

As for the code 32, not sure, I can't find what it means?

Also the thumping could be the transfer case locking/unlocking out of low sense it only happens at low speeds. It does this because it thinks the wheels are loosing traction from the info of the speed sensors. They are either worn or dirty.

A way to check this is to unplug the box underneath the drivers seat and see if the clunk still happens.

 

code 3 indicates a failing or intermittent front axle sensor on transfer case

code 2 indicates a failing or intermittent transfer case clutch.

check plug/sockets on both for intermittent electrical connection...clean and/or replace

 

One or possibly both speed sensors are bad, making the transfer case clutch being applied intermittently, causing that thump.

Remove the sensors from the transfer case and probe the resistance between the three terminals. The resistances should be about 1000, 2000 and 3000 ohms. If not, they must be replaced.