I have a 1984 300TD with 292k. The transmission was rebuilt 2 years (20k ago). I've been having an issue with a really bad flaring 2-3 shift. I replaced the K-2 Accumulator Spring and it still does it. I replaced the vacuum modulator and while trying to adjust it notice something odd. When I adjust it to the factory spec of 48 psi, at idle it stays like that. As soon as I give it throttle the pressure increases. When driving the only time it will read at 48 psi is when I'm at idle. Is it suppose to stay at 48 all the time or should it fluctuate?

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2022 Nissan Frontier Pro4x
1990 Mercedes 420SEL
1950 Packard 8

Previous German cars-
2001 Mercedes SL500
1983 Mercedes 300SD
2011 BMW 328i (manual)
2008 BMW 535xi (manual)
2006 BMW M3 (manual)
1980 Mercedes 300TD
2006 BMW 750i
1996 Mercedes E300D
1994 BMW 740i
2006 BMW 330xi (manual)
1999 E300DT Smoke silver/black 253k
2012 BMW 535i Xdrive M-Sport
1984 300TD-T 304k
1988 Mercedes 560SEL (parts car)
2010 BMW 550i xdrive
2017 Audi A4 Presitge
1979 300SD 313k
2003 E500 189k