Hi folks, I have a 2005 Legacy GT 5EAT with 188,000 miles on.. transmission shifts perfectly 1-2 and 2-3, but unless I’m at wide open throttle for the 3-4 upshift (illegal speeds) the transmission just sort of hangs out in neutral for a few seconds before slamming quite violently into 4th gear.

The 4-5 upshift is perfectly fine.

Is this a solenoid issue, or a line pressure issue (pump/other issue)?

The previous owner had replaced the in-line remote ATF filter with what looks like some random oil filter… I received a new Subaru OEM AT filter today and I’ll be swapping that tomorrow. Not sure if it’ll help, which is why I’m reaching out.

I do have access to a few “known good” 5EAT transmissions but they’re out of 3.0L H6 cars. Not sure if there’s a difference in valve body calibration between the 2.5 turbo and the 3.0L.

Any guidance is greatly appreciated.