Reading about automatic transmissions I see that the hydraulic pressure in the transmission is what causes the transmission to shift.

So that has me wondering; when I select 2nd gear manually, what is actually going on in the transmission?

It seems to me that just because you place the transmission in a particular gear does not mean it would neccessarily have the hydraulic pressure needed to shift into that gear.

If the answer is that selecting that gear manually takes the place of the hydraulic pressure then my next question is; how could the transmission NOT go into 2nd when manually shifted there?

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1987 300SDL 167k
1992 Volvo 740 140k
1990 Volvo 740 250k
1989 Volvo 240 269k

Anyone want to trade an old Volvo for an '87 300sdl?