Months ago, I previously had the P705/700 Transmission code. I cleaned the Neutral safety switch and it went away.

Recently It's come back on and I've noticed the Transmission wont shift into overdrive on the highway. Otherwise it shifts ok.

Any advice?

Thanks.

 

Both the code and your symptom are related. Cleaning can, but does not guarantee that it will resolve the issue. The unit can fail. After you cleaned it, did you follow the adjustment procedure?

I would consider replacing it with a QUALITY NSS unit.