904 Accumulator Spring

The blocker rod holds the accumulator UP in the bore and keeps it from slamming down into the bore.....which it is not supposed to do when the spring is left out. Essentially, the spring is a cusion to soften the 1-2 shift. That's how torqueflites are made They had to have things to soften the shifts because they were so badass.

What I would do if I were you: Buy TWO books. One, the ATSG Service Group book for the torqueflite. Two, The Torqueflite 727 by Karl Munroe. Even though it highlights the 727, the two are so similar, it's a great resource for the 904 as well. They are a cheap education. Get them.