Hey all, I hope I'm posting this in the most appropriate section. I didn't see any "transmission" specific wording, but I figured this is the closest thing!
Also, please know I have tried searching for this particular issue I'm having and didn't have much success. That's why I'm posting here.

Soooo... I am going to try to put this into words that accurately describe this issue as best I can. It'd be much better if I could somehow capture it on video, but even that wouldn't really describe it any better. On a normal car (automatic), you press the gas "go" pedal and the car engages and you start moving forward immediately. Duh. But more often than not, like from a dead stop I take my foot off the brake and start to engage the gas pedal. When I do, there is like this slight delay or hesitation before the gears "catch" or engage or something. And when they do, it's a violent experience inside the car. It surprises you because you're not expecting it, first of all. Second, it's pretty intermittent. I'd say it happens maybe 60% of the time. Today was the worst because I had a friend in the passenger seat with a cup of coffee... and just accelerating normally from a stoplight it did the violent lurching thing and of course, the coffee went all over my friend and my car. Lovely. He wasn't happy either and said I am a bad driver. Lol. Sorry, it's the car bud!

Is this a common or known issue for our cars? Is there any recalls or TSBs on this? Is it something that can be fixed with tuning software i.e. EcuTek? I did buy new tranny fluid and an OEM tranny gasket... was planning to change out the fluid as the car has 120k and probably has never had the transmission fluid changed (guessing since I've only owned the car for 2 months). Have some quality AMSOIL in the garage.... but could it really just be fluid as the problem? I doubt it.

I imagine if the car was brand new or under warranty and doing this, people would take it back to the dealer for a fix all day long. But since I'm not in that camp, I gotta figure something out. The best way I can describe it is to imagine if you had a manual transmission. Easy for you manual guys ... just imagine you're doing a hard launch from a dead stop... you rev it up, let out the clutch too fast or something and the car lunges or jerks violently. We've all done that before. That's what it feels like with my 7AT.

I don't want to have to buy a new transmission! I wish there were more options for us 7AT automatic guys i.e. I wish they made an upgraded valve body or shift kit like I know they make for lots of other automatic cars. Then it'd be a worthwhile purchase for me considering the lurching issues. But if there's another easy fix I'm all ears (eyes)!

It's an unpredictable and often violent lurch/jerk/lunge forward experience. And I have no control over it. And it's over in less than a second and goes into gear and shifts normally. I don't know what triggers it. I've had to try to learn to slowly engage the gas pedal sometimes otherwise I push it, wait 1 second while the car thinks about the meaning of life and why glue doesn't stick to the inside of the bottle and then BOOM finally decides to get into gear and it's not a pleasant experience. It can't be normal either. I hope it's something that can be fixed and is not just a feature of this vehicle/platform lol.






Basically, I don't know if it's the transmission or something else...

 

Do you have any exhaust mods? A muffler delete perhaps? I have a X also and when it is cold I would get jerking motion also in the beginning but after all the fluids warm up it is normal. Before a tune I would have to depress the gas pedal a lot to just get it to go but after my tune the throttle got more responsive. The reason I ask about your exhaust is that if you do have a muffler delete that will cause issues and reduce back pressure and you won’t how much torque. I experienced it and talked to my tuner and he too saw the logs and noticed so I just put my OEM mufflers back and it drives perfectly fine.

 

No exhaust mods. Really not many mods at all. I'm bone stock save for some Z1 poly bushings and upgraded control arms, sway bar, end links etc. The issue I'm having with the lurching lunging jerking behavior was present before and after any suspension mods.

It doesn't seem to matter whether it's cold or warm. It happens regardless. Just before writing this, I was just trying to pass on a highway and when trying to smash the go pedal, it's almost as if the car is in Neutral and you rev it to 5k and dump it into first gear for a really unhealthy launch.

As far as exhausts mods and tunes, you'd think any good tuner would be able to work with whatever mods your car has. So many of us have exhaust mods, I hope your situation gets remedied because I'd venture to say you shouldn't have to put your OEM mufflers back on to fix an issue that should be "tuneable". But what do I know.

 

Yeah, that does not sound normal. Try it in manual mode like rowing through the gears especially highway speeds and see if shifts better, also add some fluid to the transmission just to make sure that you have the appropriate amount. You do not need to drop the pan or drain any fluid just add some in it, turn it on let it warm up then open the fill bolt and let any excess fluid come out and then tighten it all up, and see if that makes a difference. If it does not then your transmission is slipping.
https://www.myg37.com/forums/d-i-y-i...rop-clean.html


As far as the tune it is pretty normal to lose lower-end torque if you basically do a straight pipe. I have test pipes and muffler delete and it drives fine but just barely any lower-end torque so causes a jerk into first gear, but with the OEM muffler since it creates back pressure it is fine and super responsive in the lower RPM range. Also, have to consider that we have a transfer case and front differential and it requires some torque to get it moving. The RWD guys do not have this issue since they just have the rear differential and it does not require much lower-end torque to get it moving. But, if you get an actual catback like Invidia, ISR, ARK, or HKS you should be fine as far as having lower-end torque since they have resonators and mufflers to create backpressure.

 

In my eyes, it's a transmission problem. It sounds like the torque converter isn't engaging smoothly or the line pressure ramps up quickly and that forces the torque converter to engage rapidly.
Have you used an enhanced scanner to check for TCM codes? (OBDFusion/OBDLink with the enhanced diagnostic addon does this)

Have you checked the fluid level? (I know that isn't easy on the 7AT) or maybe replace the trans fluid and see if that helps.

 

In answer to everyone who replied, THANK YOU first of all. No, I haven't used any advanced/enhanced scanner tool. I have been waiting to pull the trigger on purchasing an ECUTEK tuning kit, assuming that has similiar functionality as far as reading ECM/TCM stuff...

It's definitely nothing to do with the tune or exhaust pipes lol. I checked the fluid and it's still pretty red/pink. Basically it looks fresh. Well, fresher than the 120k miles on the car, so someone changed it before I bought it. I topped off the ATF and notice 0 difference.

I really hope I don't need a new torque converter or anything. I have been researching upgraded valve bodies a lot though. That seems like it could potentially be a fix. Sounds like our Infinitis have historically had issues with transmission shifting especially the 7AT.

FML lol wish me luck as I contemplate my next $$$ purchase for the car :/ lol

 

I'm having same issue after valve body fail and replace. From what I recall I was tuned on Ecutek they dis TCM for better shifts but when swapping in new VB it includes TCM which means I lost tune. Did you ever figure this out? I'm hoping I dont have to replace 7A after spending $1k+ on VB swap.