Hey so I have a 2012 Infiniti g37x with 130k miles I’ve had the car for a little over a year no problems at all but I tuned my car in September and after my car started shifting weird at random times mainly at low speeds (20-30 mph) and kicks when I’m going around that speed and let off the gas. I got no check engine light or anything but my mechanic ran the car and I had a P0725 and U1000 code. Any help with what it could be or if anyone knows what it is? Thank you

 

I also got G37x tuned, and my car does that also, especially during traffic. If you got tuned on Ecutek that is somewhat common, I asked my tuner about it and he even noted others have complained about it. What I did was add a diff brace, and it helped reduce that jolting/kick. But, recently I put my OEM muffler back on and the jolting/kick stopped. I am assuming it created more back pressure and I gained some lower-end torque since I was running test pipes and muffler delete only. If anything load up your stock tune, which the tuner should have, and see if it makes any difference.

 

Yea I have the same exact thing you do I have test pipes and a muffler delete but I asked my tuner and he said it’s prob transmission and when you added a diff brace did it help or fix anything? I’m gonna prob try to change the crankshaft sensors since that’s the code I been getting to see if anything changes.

 

With muffler delete + diff brace yes it did reduce the jolting/kick at the lower speeds. But OEM muffler + diff brace it reduced it a lot and the majority of the time you don't even feel the jolting/kick. It will occur at times but rarely. It also feels really good with the OEM muffler compared to the muffler delete. I also tried searching up the P0725 and only found a few threads on it.

https://www.myg37.com/forums/engine-...g-up-help.html

https://www.myg37.com/forums/engine-...runs-fine.html

 

I had very similar issue recently, car would jolt on shifts and going off the gas pedal. I did the idle air volume learning again and it really improved the shifts. This is on stock, no tune though.

 

I used to use Hypertech tune and the car would shift funny and bang into gear and stuff at low speeds. Would go away when I would tune back to stock. My GUESS is that the tunes for our cars don't tune the transmission shift logic so the engine gains power but isn't in sync with the transmission anymore and that's when you get the bangs and weird shifts. Plus the oem trans fluid doesn't handle heat as well with mileage and when the fluid heats up you get the bangs and weird shifts also. I find that BG fluid shifts so much better than the oem fluid.

 

What is BG fluid?

 

BG transmission fluid. BG is a company that makes fluids for cars. A lot of dealers, including Nissan, use their fluids instead of the oem fluids when you go in for maintenance. https://www.bgprod.com/

 

how does it compare to the likes of amsoil?

 

Can't say as I've only used the oem and BG fluid. The BG fluid shifts so much better than the oem stuff. Had my flex plate replaced at the dealer in March and they used the oem fluid and the shifts just weren't as silky smooth anymore.