It's a metering (spool) valve that can hang up. If the problem returns, it's probably scored but can be replaced and its bore smoothed but that requires a IP overhaul. Besides a lube, ATF has a very powerful detergency additive. Even works on humans, We used to overhaul lots of heavy truck Allison automatics and no matter how dirty our hands were, when tearing the trans down and wading around in the ATF a while they'd soon be clean as a brain surgeon's.:icon_wink: