Welcome to TRS
Your year torque converter should hold about 3 quarts, most years actually
In automatics Reverse requires the highest pressure to engage, 150psi
Forward requires 110psi
The ATF is what transfers this pressure thru out the transmission
The pressure is created by the pump at the front of the transmission, front pump, although there is only the one pump, lol
Raising engine RPMs increases pressure in an automatic by increasing pumps speed
So if REVing the engine a bit gets faster engagement in D or R then its most likely a pressure issue
The pumps pressure(ATF) is sent to the Valve Body, this is where pressure(ATF) is routed to the Clutches and Bands(brakes) to select "the gear"
If there are any gasket or seal leaks then pressure drops lower
This is why automatics often get slow or no Reverse engagement FIRST, but Forward still works
There can be other issues as well, just the most common issue for slow or no Reverse engagement is low pressure
Transmission uses Solenoids to shift gears, but shift trans to D or R is a mechanical selection, no solenoids involved
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