Time and practice.

What your going through is perfectly normal, everyone does it.
Everyones mouth is different, place it where its comfortable and where you can control the most air over it. Try saying a word without using your voice, just huff the word, I like "welp", or "yelp". These two words help to drop your jaw at the end and give you the 2 tone yelp,"Keeyuk". Practice practice practice.

Your probably not using enough pressure with your tongue and getting a lot of vibration, or maybe your using too much and getting a lot of squeaks and spit. Try adjusting your air huffs and tongue pressure until you can make turkey talk.