How much freaon does a 96 ford winstar take with rear ac?

Got new 3.8l and sticker on hood doesn't say how much 134a it takes to fill ac only info could find was 99 winstar with rear ac took 3 and a half pounds to fill so put 56 oz in and ac is somewhat cold but not as cold as it was with last engine the cheap walmart gauge was still in green at 45 psi don't turn red till after 55.kept checking ac after each can and it was blowing same temp of air with each can since compressor turned on. With my last engine the ac would freeze you out and now its prob 30% less cold does that mean compressor starting to go bad or other part?

Time to take it to a professional. It is dangerous to try to estimate the amount of charge by cans - the cans are sold in fluid ounces while the charge is in ounces weight… Very different things. At 0F R134a liquid is more than 18% denser than at 100F, and at 77F a fluid ounce of R134a is 1.2 ounces by weight. Charging *must* be done by weight, and as little as a few ounces overcharge can gradually destroy your compressor. Because R134a systems are governed by condenser performance there's no sensible relationship between low side pressure (as indicated by the gauge) and amount of charge. Your system may be overcharged and chewing up the compressor, undercharged and starving the compressor of oil (see the second source for an idea how critical charge is to oil entrainment), or properly charged and just suffering the effects of being improperly charged in the past. Only a professional can determine that.

Confusing task look onto search engines like google it will help