Speedometer cable problems
 

I have an 87 R20 suburban with TH400.
I seem to keep going through lower speedometer cables.
I can replace it, then after a day starts making a terrible noise. then it eventually fails. I've tried lubing the cable but noise still comes back.
Where the cable comes out of the transmission, it has to make a 90 degree turn before it goes toward the front of the truck. I'm guessing the failure is where it makes the 90 degree turn. Has anyone else ever had this problem, and what did you do to fix it.