9 out of 10 times it will be the lower cable.
The problem is it gets all the road crap. The upper one is more protected.
The best thing to do is remove it once a year, clean it, lube it and put it back carefully, to be sure it is properly installed in the transmission.
I have replaced mine 2 or 3 times since 2004.
Of course the ones you get now are not high quality, so that is another reason they don't last for many miles.
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