04' G35 4 door with auto/manual transmission.
Recently when in auto at 55 mph and up, the engine sounds like it is revving too high. When I shift to "manual" the transmission is in 4th gear. I shift it to 5th and back to "auto" and it will hold until I slow down.
101 K miles.
Transmission flush, Differential & transfer case fluids all changed @ 90 K miles.
What is the fix?

 

mine does the same thing. if you up shift real fast after moving it to the side it shoots up to 5th gear and the RPM's never change. it's normal.

 

If this was going on with my coupe I'd take her to an independent Nissan mechanic or a full on Tranmission Shop. It can't be good that your trans doesn't automatically shift into 5th gear! I would verify your trans has enough fluid to begin with since they did a flush last time it was serviced.
Gary

 

If you move from D to MM, it will always be in 4th. Every auto G35 does it, there is nothing wrong. It will still be in the top gear when in D, it just downshifts to 4th as a precaution in case you need to be in a lower gear.

 

What this guy said

But on the whole it not shifting to 5 in auto... Theres something wrong

 

Sounds like your car is normal. The gearing on the autos suck and always rev high at highway speeds. What is you RPM at 80mph?

 

Canadian and R10t_x are correct.

We need more information from the OP though. Why do we use relative terms like "sounds like" when we have a tachometer available to tell us pretty much exactly how fast the engine is turning?

So...drive down the highway with your cruise control set at 55 m.p.h. Note your engine R.P.M. Push the shift lever over to the tiptronic side. Note your R.P.M. again. It should be higher than it was before. If it's not, then your car is truly not shifting into 5th. If that's the case, take it to the dealer.

Tell the dealer the specifics you learned from this experiment. If you walk in there and say it "sounds like" your transmission isn't shifting into 5th, he might think he's dealing with someone he can take advantage of.

 

Try an ECU reset... maybe your "computer" has been programmed to shift later then what you'd like. Honestly, I'm not sure I jump to 5th until I'm above 60mph. When I drive in manumatic mode driving in 4th at 50-55mph is pretty standard.

 

When you switch to "manumatic" mode it downshifts one gear.