FYI I'm not a Ford mechanic I restore older BMW's. I have a customer who I work on thier BMW's and the also have this Ford Transit. They called me and wanted to know options on the van because the transmission has started slipping on the van any time they go up a hill or put a load on the van.
In the little bit of searching I've done it appears these vans do have transmission issues.
They got a quote from a local transmission shop for $4700.
I called our local Ford dealer and they offer a rebuilt transmission with a 3 year unlimited mile waranty.
What do the majority of Transit owners do?

 

Evening, The Transit Connect thas what is referred to as a "shuddering" transmission. Its like the system cannot locate the correct gear to be in during acceleration, cornering etc. We've tested several ATF's and found the Motorcraft fluid is one of the worst to have in these transmissions. Our last test involved using the BG products Low viscosity ATF fluid, but this only last approx 6 months.. Afterward and just recently, We've change the Fluid to the Valvoline DEXRON VI / MERCON LV (ATF) Full Synthetic Automatic Transmission Fluid along with the Lubgurd shudder fix.. we've found this combination to be working very well at the moment. The trust test will arrive sometime next week while on a 7K mile trip.

While servicing the transmission, you will need to flush and fill several times with a trans cleaner like the BG products cleaner. Then add the above fluids at the proper height. The flush and fill should be done from the top port (vent tube) located on top of the transmission. Run the system through the gears several times as the fluids need to cycle through the system and into the trans cooler. One you've clean the system then add approx 5 quarts of the Valvoline Dexron /Mercon fluid and the full container of the lubegurd shudder fix. This process will need to be done every 30K miles. where as Ford tell it's customer to return at 100K miles.. worse case, the trans shifter solenoid will need to be replaced. replacing the solenoid means one would have to drop the trans and open the two halves to access the solenoid.