Sorry to say, but this sounds to me like one of those pesky O rings has gone, which sadly means the gearbox will either need stripping and refurbing, or a reconditioned exchange box.
If that is the case, definitely wouldn't do a fluid change, it won't make it any better, could make it worse, and will cost you about £300 for nothing
__________________
2002 Mark's D2 S8 FE [Joint 1st Place Winner at 2025 Owners' Meet]
2025 Hyundai Ioniq 5 N
2020 BMW M340d xDrive
|