2004r pressure drop


New Member
Oct 20, 2023
My 2004r transmission in a 1979 malibu has pressure drop in 1,2,& reverse when rpm is increased above 1000rpm. Transmission is a CTF with CT valve body. I have a .471"
tb boost valve & .283 reverse boost valve installed. Pressure rises to 160 or 170 psi when in 1,2,or reverse when at1000rpm & drops to about 90 when rpm is increased.
Any ideas or cures would be greatly appreciated.
How are you measuring pressure?
Have you had the pump out or was this boost setup upgrade done with pump in trans?
Depending, you may need to pull that pump out for some disassembly and inspection.
Over pressure valve might be letting the pressure out, or the pump slide might be moving quite a bit when the rpms come up resulting in a loss of volume and subsequently pressure.
Depending on how deep you are willing to go will effect my suggestions.