Automatic transmission shifting issue
 

Folks,
Another query.
My 1991 Audi 100 seems to be shifting late when going from third to fourth. The RPMs reach 3500+ before shifting and then sluggishly.
any comments or suggestions would be greatly appreciated.
P.S. At what RPMs should automatic transmission shift.
as always I know the information you supply will be helpful.

[&:]
mikerike