1999 E-350 superduty v-10 trans question!

The van has 155k with a Ford dealer trans rebuild in 2005. It goes thru all gears up and down, does not seem to slip but....seems to take too much time to fully engage the next gear. For example, It takes about 3 seconds to go from 1st to 2nd....once the shift has engaged, 2nd to 3rd to o.d. is about the same lag.

This may not be a big issue but what makes me concerned is a friend has the same van and it pops right into gear, no lag. Seems to me this may cause clutch pacs to wear faster, However, I am not a trans pro.

Is there a computer adjustment for this?

There is a part on your transmission called a vacuum modulator, this part regulates when the transmission upshifts and downshifts. You have described almost all of the symptoms of this part going bad. This is the best info i could find but its about 3 years older than your van but there should not be much diffirence.

https://www.autozone.com/az/cds/en_us/0900823d/80/17/76/85/0900823d80177685/repairInfoPages.htm