09-20-2007, 05:09 PM
I noticed my main line tranny pressure has reduced from what the specs call out. The A4LD in question, is a redesigned 4.0L for use with a 2.9L engine I've been working on. After installing a shift kit into a standard factory rebuilt valve body, I noticed my tranny's main line pressure stays at around 60-75psi at 1000 RPM with the modulator set at 10" of vacuum throughout all gear ranges while the engine is warmed up. The tranny has a slight harsh shifting delay with the low pressure, I have reprogrammed the VB for hard shifting to improve performance. I also use an oversize shift improved overdrive servo kit with the valve body shift kit. My question is: Does a valve body shift kit when set for hard shifting reduce the main line pressure? From the above setup, the main pressure should be at least 115psi in drive, not 75psi according to the factory pressure specs. This reduction of pressure maybe normal since the valve body circuits have been altered from OEM designs. I installed shift kits many times before, but this is the first time I started taking the time to perform controlled pressure tests in transmissions. I may reprogram the valve body at a later time for softer shifting to verify my theory in line pressure reduction. In the mean time, I can't seem to find any answers about shift kit reprogramming and it's influence on line pressure.