It's my understanding that the cable helps to make the seat slide squarely front to back, both sides travels at the same rate, not crooked.
My 48 seat frame has the same arrangement, but I haven't worked on it yet.

Grigg


•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-