Won't shift into 5th gear or over drive.

https://www.youcanic.com/nissan-transmission-problems/

First check the transmission MIL code , that will tell you if it is the Over Drive lock solenoid mal functioning , Do a tranny oil change with filter ,then replace fifth gear pressure solenoid , when you are there already .

Please don\'t try to adjust your rpms. Its computer controled and it just won\'t be good at all. Not to mention hard for your drive line when you shift into gears.

Just fix your heat, its the best option.

HI,
Search online..but it sounds like the 'synchros' in the transmission are going/gone.
Also, the clutch may be wearing out.

Td

No. You are set by the gear ratio in the transmission and the final drive. The only way to change this would be to change the final drive ratio in the transmission, and there likely are no aftermarket solutions available to you.

Pull the trans,strip it down & replace the worn parts,
like the synco rings,that should be obvious

You don't need the engine running or drive it, to try & shift
through the gears

sounds like the rockers or lifters have some play due to wear.you don`t say what rpm you are shifting at other than high rpm.by changing the oil you have increased the viscosity of the oil as its new and not dirty and thin and cold oil is thicker than warm oil.you might want to try a heavier oil to see if it helps.you may not get this noise out unless you replace components or adjustment of rockers if they are adjustable.if its not very bad you may have to live with it.

Its a manual trans right? Those are probably worn syn rings in the transmission, or a loose throw out bearing on the clutch. but if it was a throw out bearing it should be happening in all gears. So its probably worn sync rings in the trans. this means you need your trans rebuilt. go to a local trans shop. to make it shift easier for now, try to match the speed of the car with the speed of the engine. what i mean is when upshifting to 5th gear, wait for a sec til the engine drops in rpms to shift (wait til the rpms are they would be right after you shift into gear). This will allow you to shift without syncs, and make it an easier shift. don't worry its easier then it sounds. but best to get it fixed

Sounds like the clutch is slipping. If the clutch is bad, it will slip in high gears (4th & 5th) but seem to work fine in lower gears. Clutch probably needs replaced but have a mechanic check it out first because it's a fairly expensive job. If your clutch is actuated via a cable (not hydraulic), it may just need adjusting.

Looking at all your probs, my guess is you have the wrong transfer case! It may be one for a diesel! Frankster016