I am replacing the differential in my transmission with a limited slip.
The factory manual shows the location of the mating number the backlash and the deviation from blue print.
My pinion shows N17 (deviation) and 717 (mating number) the ring gear states 717 (mating number) and TK for the backlash?
The backlash typically would be a decimal ie .17 I have never seen letters.
Anyone ever seen this, and if so what does it mean?

ps: post number 914
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Thanks in advance.