1994 Diff Question and tranny question

I wasn't sure but i wanted to change my gear oil and tranny oil to possibly RoyalPurpal or somthing that is nearly as good. My truck has about 127,000 on it and wasn't sure if this would be safe for the truck or should i just stick to the regular stuff? I know the diff hasn't been drained and filled but the tranny was done about a year ago and i wanted to do it befor winter of this year. So please any and all information is appreciated.

ThankYou

My 90 K1500 has about the same mileage. I run the regular stuff. I worry about leaks with the synthetic stuff.

//2000CAYukon

Yeah that is what i was worried about, but alright i'll just stick with my reg stuff atleast untill i get enough money to change the seals on the dif and all that then i might consider running the Royal purpal stuff. Thanks for the help man it's greatly apprecaited .

Marsal

I prefer the old petroleum base fluids myself. The synthetic stuff has proven no gains in my older vehicles.