I decided to post this thread in hopes that it would help anyone with a Nissan VQ35 engine set up experiencing similar symptoms.

Issue

Customer from Ibadan called to state his 2004 Maxima suddenly lost power while driving.
He had switched the trans shifter to manual mode and found the car stuck in 5.
Turning the car off and back on still had the car starting off in gear 5.
His mechanics had informed him a new transmission is required but he wanted to seek my opinion first.

Solution

The symptoms being familiar to me, I assured him he would not need a new transmission and asked him to have the car scanned. I expected feedback of camshaft sensor codes and was certain these were the culprits from my experience.

He had it scanned. No camshaft sensor codes, no transmission codes. Just o2 sensor and EGR codes.
I however assured him it could be fixed with new camshaft sensors and had him manage to drive it to Lagos yesterday to have it fixed.

He arrived yesterday and I immediately replaced both camshaft sensors on the car.
We started it, and the car drove perfectly for 5 minutes and went back to its stuck gear 5 state.
At this point, I rescanned the car and now found code p1574 which points to one of the revolution sensors on the transmission.
There are 2 of such sensors on each side of the transmission. One for input speed and the other for output speed.
They are identified with codes P0720 and P1574.
At this point, I checked the wiring of the identified sensor and found a break which we taped up.
Erased code, started up the car and everything was back to normal.

Customer returned to Ibadan today and called to inform me of a hitch free trip.

This is just an awareness post to enlighten users out there that several sensors affect transmission performance and unusual shifting in Nissans/Infinitis and these should be extensively tested before attempting to change a transmission.

I have seen customers replace a transmission with N450,000 when a N15,000 sensor(new)/ N7000(tokunbo) was the culprit.

Peace

Keep it up

Nissparts: can you comment on the link below. Thanks

https://www.nairaland.com/1352077/what-should-aware-nissan-xterra