AL4D hard 2-1 downshift

[cfkane]

I am on my 3rd AL4D transmission in my 1993 Explorer with one common periodic problem with the 1-2 upshift and 2-1 downshift. At times, when warm, the transmission has a hard shift, particularly during the 2-1 downshift. The downshift is delayed and hard enough to trigger the ABS pump. Although the occurrence is increasing in frequency it is still not consistent. Given that 3 different transmissions have experienced the problem I am looking elsewhere for the contributing cause. Has anyone experienced this problem and if so what was the cause?

 

[cfkane]

Using an adjustable vacuum modulator solved the hard shifting problem.