I have a newer Platinum horse trailer. My ramp, rear tack door, and LQ door squeak horribly. It is so loud! I called Platinum a year ago and they said to put zerts in the hinges. We did that and lubed with liquid wrench, but the squeaking is no better. Any suggestions? 

we had the same thing but on our elite. The trailer shop said the hinges are too tight and you cannot fix it unless you cut a slit in the hinges. So we did, cut a thin, vertical slit in the hinges with a metal grinder, put a piece of aluminum tape over it and you cant even tell. It released the pressure and they dont make any noise

Might try using a grease gun and really force the grease into the hinges.  We have broke off a drop down before because they were so tightly made.  I don't remember how they took the others off but they did and then ground down the inside part some to give it more room.