Problems With Manual Tranny?

I Have A 96 Sierra With 4.3 V6, 5 Spd Man. After Sitting For Three Days I Had A Hard Time Getting It Into 1st Gear And Somtimes 2nd. After About 40 Miles It Cleared Up, But I Changed The Man. Tranny Oil Anyway( Way Past Due) Has Anyone Else Had This Problem? Or Was It Due To Old Oil, Cold Temps And Sitting?

I would put my $$ on the temp. and old oil. I have had new trucks that shift hard when it gets cold out. the oil most trans`s use is 90w that stuff is like molasses to start with.where you live it may pay to look into Synthetic oils they are usually thiner and lube alot better and cost a little more but the time between changes are a lot longer.

Changed Manual Trans. Oil, It Was Low Also, And It Worked Like A Charm! (pennzoil Synqromesh Man Trans Oil)

does it shift in and out of 1st& 3nd when the engine is off?? if so the clutch isn't releasing all the way, check the fluid reservoir