I recently purchased a 2009 G37 with 40,000 miles. First week, car ran beautifully. Then, while driving at 45mph, the trans did a hard downshift, then engine stalled, car coasted to side of road, engine still running, but would not rev above 2,200 rpm. No warning lights came on. Shut engine off, waited 1 minute then restarted car. Could now rev about 2,200 rpm. Drove off and car was fine. Took it to the dealer, No DTC's.
Same thing happened about 1 week later; hard downshift, car begins to lurch while slowing down and coasting to side of road.
Back to the dealership where they gave me a courtesy car G37. They called after having the car for 2 weeks and said they found coolant in the trans, so they are replacing the valve body. Still waiting to get the car back.
Yesteday while driving the loaner G37 at 45 mph, the identical problem happened; hard downshift followed by lurching and no power. Engine does not die, just will not rev above 2,200 rpm and I have to coast through traffic to side of road, turn the engine off, then restart, it reved above 2200, so put it back into gear and continued with no problem. Has anyone experienced this downshift, stalling problem? The dealer cannot duplicate the problem, but because I mentioned the hard downshift prior to stalling, the opened the trans and found coolant. Comments would be appreciated.
Thanks.

 

Buy a 6-Speed?

 

I'm expieriencing a similar issue, however it is like a backfire and then car bucks. It happened on Dec.23 and then on Jan.3 2011, both times the car would not go above 2400 rpms, when I got to my destination (I shifted manually) I switched car off, left for a couple of hours then went back and no issues. In between occurrences I drove about 500 Kilometers and i trip was about 120K each way. Today I filled and put in 2 gas line antifreeze (maybe water) after I filled tank. I haven't taken to dealer yet as I am sure they would not be able to do anything until they can replicate. My G is a 2009 G37X Auto that I have owned since new and now has approx. 40,000KM. No lights came on the dash. Any help?

 

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Do they have a theory of how the coolant went into the trans?

 

I asked the dealer that very question. He said they will be replacing the radiator as well as they feel that is where the mixture of trans fluid and coolant came from. I advised the dealer that their loaner (2009 G37 with 20,000 miles) did the same thing yesterday. Therefore, I am really dubious about the problem being completely related to the trans. The hard downshift occurs first, then the car slowing down, does not respond to the pedal, then must be turned off and set for a short period (60 seconds) then upon restarting, runs perfectly.

 

Based on what you are saying, this could be a common problem. Design issue?

If they found coolant in the trans, then there must be a leak somewhere. Did you noticed abnormal coolant level in the coolant reservoir/radiator?

 

When I purchased the car, I noticed several fluid items at a lower level, i.e., coolant, brake fluid and wiper fluid. None of the above were seriously low, just below the max line when cool. I topped each of them off.

 

Took my G to the dealer today as transmission bucked again on Saturday. They said they received a new program from Infiniti on the weekend and they installed this program on my transmission. I was told to drive it and we will see if it helps.

 

Finally got my 09 G37 back from the dealer after 3 weeks. They put in new trans and new radiator. So far I have put about 300 miles on it without a hint of the old "hard downshift and bucking" problem. Really hope this repair solves the issue.

 

Wow, at least you got some new parts out of it, should solve the problem.

JG

 

This is a lawsuit in the making right here. They are putting you in a dangerous vehicle. If this problem coincided with a scenario that required some evasive driving, or the like, it could mean your life.

Personally, I would make a strong stance and tell them you intend to return the defective product they sold you.

 

I read about this problem a year ago in several members of this forum who posted about it.. then their posts stop cropping up -- dunno if their problems were resolved. I JUST posted a thread about this:

https://www.myg37.com/forums/g37-sed...azy-again.html

My car did the same thing twice.. JUST today got it back from the stealership -- could not replicate, bla bla blah.

They did not open the tranny .. just did the latest tranny TSB and FWIW, it's driving like a champ now.. smoother downshifts.. occasionally harsh.. not perfect by any means... and I consider my wife's '08 G35x 5AT PERFECT in terms of how smooth that tranny is... and LESS of that rubber band dragging feeling when coasting to a stop without applying the brake...

I think this is a system wide problem, and more symptomatic trannies are causing this to happen. See my thread re: details of my ordeal.

Same deal with me.. would not rev past 2200 rpms... no check engine lights.. no codes... weird.

 

Good luck with that one.. if they can't replicate the problem, there ISN'T a problem legally. I have been down the lemon law route with my '02 Acura TL Type s with a KNOWN and confirmed transmission problem that put me in similar dangerous scenarios.. it is VERY hard to accomplish what Myoctye is suggesting without reproducible evidence. Just my $0.02.

 

Your 2 cents is definitely good, especially because it comes from personal experience. I guess I was just saying that I would cause a huge stink about it. haha.

 

Is there a direct conduit for coolant into the transmission case??? why would coolant be in the transmission? I thought only tranny oil was in the transmission of an auto trans.