Posting for a friend:

My 84's 700r4 is acting up. If I am taking a left turn (only a left, it won't do this on a right, WTF?) at a speed of 40 mph or more... when I roll into the gas in the turn... the tranny goes into neutral! The revs go up to 5000... so I let off because as soon as I straighten out, it dumps back into 4th (or 3rd).
Also... my car will shift wrong sometimes (I shift manually because it will almost NEVER downshift correctly) for example I was doing a WOT test and on the 1 --> 2 shift I clicked the shifter into "2"... it shifts... then shifts BACK into 1 (I am shifting at 6000, my motor will rev to 7000-7500.. it's a built 327... but my manifold is an Edelbrock Performer and really doesn't pull past 6000) ... so I have to let up to get it to shift back into 2nd or I'll go deep into the 7000s...

It also won't shift from D --> OD at WOT, but I've heard that is a "Designed behavior".

Will a transgo shift kit fix my problems? Or what?

The tranny fluid level is fine.

 

You might have some better luck on the transmission board.