740 turbo 1991 158k stalls

[tranny]

1st timer here. my daughters 740 runs but shortly stalls. It appears after observation that it will run for about 10-15 minutes and then stall. run again but stall sooner and then sooner and finally not start untill it sits for some time. when its running it runs smoothly. I replaced the fuel filter at the tank with no change in operation. What do you think?
with much appreciation, tranny