1967 R/T and when sitting for more than a few days , when starting in park, it would not go into drive or reverse very well. Putting it in neutral, while running, it would engage just like new. Rebuilt a newer BB727 and new converter. Swapped the valve body from the old to new trans. Issue is actually worse then before but going to neutral fixes the issue. The only common denominator is the valve body. Can this be the cause? Thanks in advance. Addition. I drove it for about 25 miles yesterday and when starting in park it didn't want to move. Worse than before as if I drove it daily or within a few days, there was no issue.
Some guys drill the valve body at the torque converter regulator valve and this will cause a more rapid converter drain.
Warm it up and drive it, then verify the fluid level in neutral before shutting the engine off.
Check the fluid level the next day before starting. If the fluid is very high on the stick then likely you have excessive drainback.
Start it and once you get a good engagement check the fluid again, it should be much lower now.
Excessive pump face clearance causes this as well.
