I wouldnt spend any time looking for a ground if I had a manual t-case sitting around. We changed the t-case on my sons 95 f-150 and he says it was the best upgrade we have done to his truck. No more looking for a bad ground, worrying about breaking wires off, shorting something out doing water crossings. Just a better way to go. the reason we changed his was it went out on I-70 not using 4x4. hadnt used the 4x4 in weeks and it just went. That is what I would do.