It runs rough, and no check engine light is on.

[don-ohio]

1/4" of play in the U-joint is REALLY BAD. If you're talking the play in the rear end/drive yoke, it's okay .
Get the rear wheels off the ground and THEN check circular play of the front and rear u-joints.
don-ohio

 

[Malibumax]

Hi Don, thanks for the reply. I did jack it up and there is between 1/8th and 1/4 only in the rear end on the driveshaft... where the yoke goes in to the trans there isn’t much of anything movement wise. This is why I am baffled. No check engine light is on. I’d figure if it was the torque convertor the light would be on. And, I know if the torque convertor was bad there would
Be more of a shudder than a vibration. The trans shifts fine. No clunking when put into gear, and no whine either. Any other ideas? Do you think it still Could be the u joints?

 

[don-ohio]

The plastic cooling fan can lose a blade,or the fan clutch could be coming apart. I've replaced the fans on both my Aerostars because of cracks. I also replace the water pump and fan clutch at the same time, and new antifreeze solution.

 

[don-ohio]

Also, a drive shaft can be slightly bent and really show off at higher road speed.

 

[BrooklynBay]

There aren't that many transmission codes for the A4LD transmission since it only has two solenoids. The later version 5R55E has an internal turbine speed sensor to throw codes when the speed signal doesn't match what it's supposed to be displaying.

 

[don-ohio]

So, Brooklyn, some of the Aerostars had the 5 speed trans they put in the Lincoln LS? I don't really like that trans for an Aerostar.

 

[BrooklynBay]

They didn't come with a 5R55N.