Maybe, maybe not...There's the boost valve and sleeve that can be swapped out with the transmission still in the vehicle...You'll need a small pair of interior/exterior snap ring pliers to do it but it's not difficult...A worn boost valve will cause the issues you're having as well...I always replace those pre-existing boost valve and sleeves with the
Sonnax large ratio boost valve kit - it comes with a higher pressure spring for the PR valve and gives you about a 10% increase in line pressure at all throttle angles...Transgo's boost valve does the same thing...If this trans already has an upgraded boost valve then yes, more than likely you're dropping the transmission to figure out and fix the problem, but a pressure test will definitely help you narrow things down and give you some baseline data for your diagnosis...Having a bi-directional scan tool plugged in at the same time will also be very helpful.
Here's line pressure testing instructions.
You're looking for pressures at idle to be within the ranges shown on the chart for each gear shifter setting and immediate line rise up to around 150-175PSI or so at WOT.
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