Your 92 gmc makes a sound like an old speedometer cable would but when you took the instrument cluster off there was no cable what else would it be only makes noise when pushing on gas sometimes when?

I had the same problem but it is really not a big deal . T went to my dealers and they said that it was just a drive belt ratating . Just oil evey belt once and a while and you should be fine . If that does not work , contact your dealer .