Light miss/ shudder under light load

Please help. New to the Windstar forum as I just bought it this week but have been active on the Silverado section for years.

I bought a 2003 Windstar with 144,000 miles. I had to wait until it got back from the dealer for transmission repairs, as it was shuddering in overdrive. It still shudders above 40 mph when convertor locks up. Lower speeds the convertor pops out (unlocks), above 60 it doesn't. Feels like an engine miss to me. Heavy loads it runs smooth, but steady cruise or light tip in it shudders, in or out of overdrive. I can't get it to miss when stationary. Wires and plugs look good but it has Motorcraft platinums installed. Any ideas from someone with similar issues in the past? Thanks!

The Dealer must of did a patch job on the trans. Mine doing the same thing and fluid leaks when trans gets hot. Taking mine to a tranny shop on Monday.
If you get a blinking engine light than the coil may be going bad other than that it most likely your trans is not fixed yet.101,000 on my 2001 so its seems about time for a new trans.. Let us know what you find out. Gary

Non Merc-V rated ATF will cause the shudder you describe. Overfilling can cause foaming and shudder as well. If the TC is jumping in/out of lockup, like you say, you could have an engine problem. Is the SES light lit? Have you checked for codes? A misfire will prevent TC lockup, but you would have a SES light/codes associated with it.

Joel