I was driving today in my 2004 Ford Freestar van when all of a sudden the transmission stopped being engaged. I pulled over, no problem with the moter, but it would not slip back into drive reverse etc. No warning lights or anything- just a quiet whine when i pressed on the accelerator. what is the problem? Does this mean a new transmission? Only 70,000 k's on the van...

Sounds like perhaps the splines on the torque converter output shaft may have failed, there was a recall on some of those for that very issue. Here is a news article about the issue:
Ford is recalling certain model 2004 and 2005 Ford Freestar and Mercury...

The cable HOUSING has become loose from the anchor point. Get under with a hammer and a pliers and put back in place. Then persuade it to stay in place.

Pull it from the bottom it's way easier drop the cradle and lift the van up and over the engine

I would have it towed to a different shop for a second opinion.
To start at the beginning, if it works in reverse but not drive the linkage is working.
When you put the transmission in low or second you are bypassing most of the sensors and valves. You put it in first or second gear and it stays there.
It could be a long list of things from the valve body to the pump to a solenoid or sensor.
There is a good chance the problem could be fixed without needing an overhaul.
You never take a knife to a gunfight, so you wouldn't have anybody but a transmission shop work on a transmission.
When they recommend an overhaul, they are pulling your trans out and replacing it with someone's rebuilt out of the crate. No worries on their part.

This is a recall just like the 2005 Freestars. Your Freestar more and likely has a defective torque converter and worn out splines in your transmission. This is a life threatening recall and Ford inc has been looking at it as a casual recall. Get this to your Ford dealer today and have them fix it at no charge to you. Problem solved.

You need a new Transmission . The output shaft of the transmission is worn it will not mesh with final drive gears.

it sounds like the transmission is gone out !

Go to town hall on edmonds.com and look up 2004 Ford Freestar engine problems. You'll be amazed and sickened. Follow-up with NHTSA.

if the check engine light is on you can have it scanned to take you to the problem.if no light on you need to check your plugs,wires,and coil packs.

All you need is a 13mm boxed end wrench. The tensioner pulley is the one all the way on the bottom towards the rear of the van. You can reach it under the van. Slide under the van in front of the passenger front tire and you will wee the pulley. Put the wrench on the bolt and pull towards you to release the tension on the belt.