TH125C low line pressure after installing shift kit (Page 2/2) James_GT JAN 18, 07:37 PM Hi Marc, TC feels like it may be slipping at around 1/4 throttle in 3rd gear, and sometimes I'll hear whirring under acceleration at low-mid RPM. Everything seems normal and responsive if I drop back to 2nd and accelerate, but then the 2-3 upshift is soft or flares mildly. If I let off the throttle completely before this happens, there's a solid 2-3 change. I'm not sure why that is, aside from maybe the line boost valve kicking in when I release the pedal. Int/rev boost valve is installed in the correct orientation. I can see from my reference photos I had it pointing in opposing directions to the pressure regulator valve, with the stem facing inwards. Will check again next time I have the VB apart. I haven't touched the aux. VB on my Fiero trans, but I can open it up and inspect the pump slide/priming spring. I actually have a spare VB now from an '87 Holden Camira TH125C to play around with. I've thought about trying it out, but that one has its own issues (stuck boost valve sleeve and needs a thorough cleaning). Probably will just keep it as a last resort or for parts. I did disassemble the aux. VB on this one to familiarise myself with the components you're referring to. I hear you. I won't rule out something breaking, even if it worked before. I'm getting the sense after 36 years and over 125k miles, maybe the seals are overdue for replacement anyway. The shift kit increases the amount of oil distributed to certain parts, so it could also be revealing problems that were already there. Haven't touched the L/R apply tube either, but I will check the o-ring and air test the L/R clutch. I'll go back to the VB first and swap the pressure regulator valve while I'm there, just to be certain it's not contributing factor. OldsFiero JAN 20, 09:50 AM The 2-3 shift will be firmer when you lift because engine torque drops off before the line pressure can drop off. I see that we have more symptoms now. Some gauge fluctuation is normal with this system. You are now noticing a whirring. Does the gauge needle fluctuate very rapidly( almost a blur)? Have you checked the fluid level right away after a hot drive? Were there any fine bubbles in the oil on the stick? Did you replace the filter? I have seen defective filters more than once. Look for cracks in the plastic filter body. I know the filter is submerged in oil when properly filled, but the pump creates enough vacuum to pull air down through the oil. I have seen it. I have seen scraps of filter media (I think from when the shape of the media is stamped out) restricting the outlet of the filter. A fleet mechanic once serviced the trans on one of their Celebrities. After he filled it, he went to run it through the gears and couldn't move the shift lever. They had it towed to me and we found scraps of media blocking the manual valve in the channel plate. Smaller pieces went throughout the unit. Some of it even made it inside the clutch drums! I cut the filter open and the media was intact, but there were still some other scraps still inside. Thankfully I didn't install that one or I would have had to eat that job. I could write a book. Assuming the oil and the pan are clean, you could remove the filter temporarily and test line pressure. Enough for one day, Marc James_GT JAN 21, 09:33 PM Okay, that makes sense about engine torque being ahead of line pressure when letting off. Line boost valve probably works the opposite way to how I described in my last post. As I understand it, the line boost valve boosts pressure when the accelerator is pressed and not at closed throttle. The shift kit required bending of a tab upwards on the bell crank, which I assume reduces line boost for longer to prevent late shifts. Yes, that's correct. The gauge fluctuates very rapidly within very close range of the pressure it's at (+/- a few PSI), like a blur. Sounds like the flickering is just pressure being regulated and nothing unusual then? It's only steady at the lowest pressure in the Min T.V cable position. On one occasion during warmup the needle would switch back and forth for a couple of seconds at a time between 70 and 110 PSI (in D at Min T.V), not sure what was happening there. It was as though the int/rev boost valve was kicking in when it shouldn't be. I checked the fluid level after the trans is hot and confirmed the level is within the hashed area, with no fine bubbles on the dipstick. Yes, replaced the filter and filter seal a couple of times since the shift kit install with the same results. Hoping it would turn out to be something simple like that too. I'll take all your advice into account next time I'm working on the trans. Just waiting until I can get a hold of another pressure regulator valve, then I'll be right back into it again.