Help please??? Shift issues
 

I just got a 2004 infiniti g35 sedan. Awd. My girlfriend wanted a new accord and I talked her out of it for this one. She loves the way it looks and drives. BUT... It seems to have some issues. Here's the rundown. Car had no check engine light when bought it. We've only out maybe 400 miles on it. The car seems to hesitate shifting around 35-40 mph. Then when at around 70 it's taching about 4500 rpm. Sounds like would blow up is ran 80-90. I put over to manual shift and it says its in fourth. I shift to fifth and no change in sound. Then go back to drive. If go back it always shows only in fourth gear. When first was doing it I read about can sensor causing similar problems. I replaced it but no change. Then the check engine light came on. Only code is for oxygen sensor then. I then was told maybe throttle position sensor. So I got a whole throttle body and replaced it. No change. Tried to do a reset of tps and still nothing different. Have heard crank sensor could cause issues or the gas pedal sensor. Haven't replaced either. But don't want to keep throwing parts for nothing. Took to autozone today and he got here codes. Said was showing the transmission sensor and something else about air flow and engine not reading something. I'm just hoping someone on here has had similar issues or knows what to look for or maybe some way to check so I don't keep guessing. My girlfriend loves the car but she's getting ready to dump it. And really can't afford a new car. Someone please help. Also if it is the tcm is it located in tranny pan or under kick panel. I've heard both on 2004.

If your cruising in fifth (drive) and push the stick over it always downshifts to 4th. 5th is not much taller of a fear then fourth it sucks. You are abnormally high in rpm though for the speed.

Also, check there are no vacuum leaks or intake pieces loose.

Thanks for that info. I didn't realize it would always go to fourth. Made me think it was something in transmission acting up. Web in manual mode I shift to fifth it doesn't seem to change much. And yes it tachs way too high. There's no way at that I could get the car to 90 or more without blowing it up. Something's wrong for sure. Any suggestions?

Would vacuum leak cause it to shift bad or do those things with tach?

Techs who have a tool that can read advanced obd2 data from your car might be able to figure it out. I can't say from this far.

If yours is a 2004.5 or newer it has the TCM inside the trans
2003-2004 models are located under the passenger kick panel

Sounds to me like you have slipping in the transmission, probably the 4th gear clutch packs if you are driving slow and you feel it start climbing RPMs around 35-40. It is possible that it is a problem with the Transmission valve body as well though

How many miles are on it? Most transmission shops have a reader specific to transmissions and can isolate the problem.

Post up the code that you had read at the Autozone