In the manga, gamabunta henge intoa fox that has only one tail+ Naruto's vision(will), so it is possible gama doesnt know what he henge into . But I wonder after changing into 9tails in the anime contradicts that he doesnt know, granted he cant see himself but its quite illogical if he can utilize nine tails and ninetail is the trademark of that youma that possibly gave him that fat scar over his eye. And the saying is , scar symbolize a grudge or, and, rememberance.