97 Suburban R134a Capacity

[86Monte]

I own a 97 suburban LT K1500. Love it. The AC has never been that cold. Just drained it, checked it, and pumped 3 cans into it. Runs like it did when i first got it before it started leaking, and still not that cold. I read about the A/C switch, but I think it's evenly cold front and back. How much R134 does it take to fill this thing up? I'm only wondering because it's not that cold and I'm sure those rear A/C lines hold plenty of refridgerant. Total capacity is?

[cammiller]

4 lbs.