I had this car for nearly 15k and have exactly the same problem so it doesn't seem to be getting worse

When I reach about 50mph, transmission sometimes gets stuck on 3rd gear (when I don't go over 50), when I go over 50, transmission switches to 4th gear. So the problem is that at 50 it does not switch to 4th right away.

I changed transmission fluid before.

You think it could be some sensor?

 

try getting it flushed, might have a sticky valve in it

 

Thanks. You think it will be better to use some syntetic fluid instead of oem fluid?

 

Do some snooping (FSM?) and find out what factors go into causing the transmission to shift. There could be several as a fail-safe. There could be one that says "no matter what, at 50 mph, the car must go into 4th gear." There could be others based on engine rpm, vacuum, etc. Figure out what the others are and using a schematic, follow those to sensors and switches. If you meet me halfway and find the documentation, I'll be glad to do the diagnosis part.

 

Thanks, is there any better transmission fluid that I should use? What are you guys using?

 

I would not do a flush on a front wheel drive car. It is highly frowned upon. Do a couple drain and fills and change the filter and if it doesn't change anything, take it to a pro and get an opinion..

 

It's my understanding that flushes are ok if they have been done regularly as prescribed by Nissan -- however if you are doing your first one at 100,000 miles, that's recipe for disaster.

 

Yes I agree. You can do them regularly from about 30k and up but don't start at 100k miles.

 

where is transmission filter is located?

 

Inside the pan, I believe.

 

Thanks, I don't want to open the pan up for now though. Where is the best place to get transmission fluid? Local dealer or there are better deals online?

 

I would say get the tranny fluid from Nissan, and definitely don't do a flush. Just drain and fill two or three times

 

wish I'd read this a couple days ago... I did a full flush and filter replacement on my 2002 I35 at 173K miles, gulp.

 

As a note, it's not really a filter. It is by definition, but it's more of a screen. Also, you can remove every bolt for the screen except one (unless you're lucky). That one is put in "backwards," as in, the nut if in a position you can't get to unless you take apart the transmission. I recently went though this, just did a drain/fill a few times with AMSOIL (and can definitely tell a difference) and cleaned the magnets off that are inside of the tranny pan.

 

I have a 2003 i35 wit 128k miles and am traying to rebuilt my transmission and i wana makeit stronger, like afther market part or someting like dat wat u guys tink

 

Since this was bumped... Forgot to mention that ours in in 4th by roughly 40mph if I'm easy on acceleration.