96 taurus help! Stiff Power Steering

1996 ford taurus GL 3.0l
Power steering becomes very stiff, do not completely lose but very hard to turn wheel, after exceeding speed of about 30 mph. If you stop the car, shut engine off and restart, power steering returns (as if a solenoid was stuck). Changed power steering pump/res, Return side hose and filter (dealer parts). Is there a speed sensor for steering that could be bad? I was told that the rack needed changed, $500+ damn!
I also have an anoyance problem with the transmission. When I come to a quick stop, the transmission bucks forward as if a slow downshift. Took to a transmission shop and they found nothing wrong with the transmission and said it was a bad speed sensor?

Have you been flushing the oil on the Power steering and the transmission? You gotta do that once a year if you don't want trouble.

I am having the same problem with my power steering. It works fine when I first start the car, but then it gets very stiff. I've changed all of the hoses, pump (twice) and the rack and pinion.
Could the power steering pressure switch cause this problem?

how do you flush the power steering?

Your Power Steering Rack is going south, time to replace it........

It was a faulty GEM module.

whats a GEM module?

whats a GEM module?
It's a "Generic Eletronic Module" and it is located behind the fuse box.

I don't know if this will help or not but worth trying it fixed my int power steering problem....replace the transmission range sensor also known as the nuteral switch. hope it helps..