94 Caravan - cooked transmission - cause?

Base info... 1994 Dodge Caravan, 3.0L V6, 41TE 4spd tranny running
ATF+3. B&M Aux tranny cooler designed for towing up to 7k lbs.. 103k
miles on the van.

I pulled a 2200lb popup camper from Daytona Beach to Brooksville in
Florida. Didn't really notice any problems. Went to go back out, and
the tranny started to shift funny. Bouncing bewteen gears.It did this
for a few miles, and then ended up losing all gears. Going to neutral
for a few seconds, and then going to D would bring a few moments of
movement until it lost it. Once it picked back up, the tranny would
whine for a few seconds, and then go quiet.... drive would then resume
for a few seconds, then go away..... repeat repeat all the way back to
the campsite. (About 10 miles)

Scanner revealed a Loss of Prime error, 4th Gear ratio error, and
Torque Converter Lockup error.

Fluid was clean smelling, but darkened. There was a lot of debris in
the fluid (clutch material).

Had the van towed home. Dropped the pan, and the magnet was covered in
clutch material. Changed fluid and filter, and drive is restored.
CVI's are all within spec listed in the 94 FSM.

A couple of months before this, I noticed a chirping noise coming from
the engine compartment. I just thought it was a bad belt tensioner,
and was waiting until major tune up time to change it. Now, after this
disaster, the noise is more pronounced. Its the tranny. Noise is only
there when in R or OD/3/L.

When driving slow (under 10mph), the tranny feels like it is catching
and releasing. Chalking this up to toasted clutches.

So the tranny is cooked. Question is, what caused this? Yes, I did tow
in OD. Florida is 90% flat land. When going uphill, I pulled it down
into 3. (Even in 3, according to the scanner, the TCC never stayed
locked...)

 

Honestly, I'm suprised it lasted as long as it did. That transmission
wasn't designed to pull much more than gross vehicle weight.

 

He right ^^^^ Ive put alot of them in.

 

Sounds like it just slipped under load. Generates a lot of heat and burns
off the clutches. In a few seconds, it's over.