What's up guys, I'm in need of some help here. I have a 2006 G35x with about 94,800 miles on it. Recently, my car has been shifting rough and jerking in traffic, almost like it doesn't know when to shift. If I'm cruising at a steady speed/highway everything is fine, it's in traffic or sometimes around town where I notice the issue. If I'm in traffic and lightly touch the gas to move forward it'll jerk a bit when I'm about to brake. If I move enough to get into 2nd gear then brake in traffic, sometimes the downshift is rough and I can feel it in the car. I have been watching the RPMs and immediately after I let off the gas, they go down and then jump a few hundred before returning back down.

I have not changed the transmission fluid since I purchased the car at 75k, Infiniti did not have any records of it being changed. The atf fluid level is in the hashmarks and it's a light brown, not too dark and doesn't have a burnt smell to it or have any flakes. I was hoping it was as simple as low trans fluid but I followed the service manual to check and it seems to be normal. I do not have any service lights on the dash either. My car is just rough and jerking when I'm getting off/on the gas sometimes and when I am braking soon after. If I am moving slow it'll shift early in traffic and jerk, almost like it doesn't know what to do. Seems to be most noticeable in low speed with stop and go or in traffic, it really sucks and I can't figure out what it could be. Accelerating with normal shifts feel fine, and so does driving on the highway. I do not feel any slipping or rough shifts normally, it just gets bad in traffic. Please, any help or insight is greatly appreciated. Thank you guys for the help as always.

 

First thing I would do is a trans fluid service. ONLY do drain/fills of the transmission fluid, DO NOT get a transmission fluid flush. Probably best to do two or three drain/fills to help get all the old fluid out. One drain/fill is about 4 quarts of fluid. Do you have any check engine lights? AT check light?

These transmissions were designed for Nissan Matic-J (and there are stickers all over the car stating so), but its been discontinued by Nissan and they recommend Matic-S. Matic-S, as I've read, is full synthetic and was designed for the newer 7spd transmissions (G37/370z), and it has different additives for softer shifts and is lower viscosity like many of the newer vehicles ATF's. Nissan claims it is compatible with any car specifying Matic-J, which is believed to be semi-synthetic. I've been running Idemitsu Type-J (designed to meet Matic-J fluid specs), and it works really well for me.

I've tried/used all three of the fluids, I prefer the shifting performance of the Matic-J & Idemitsu Type J. The shifts are firmer and more consistent (in my experience) compared to the Matic-S fluid, which I personally prefer. BUT, my transmission has over 173k miles on it, so the higher miles I have may account for why I can feel a difference in shifting. With less than 100k, the difference might not be as perceptible.

 

Thanks for the reply. I do not have a CEL or AT check light, the dash is clean. Do you really think the fluid would suddenly just cause this issue? I know it should have been changed, but it's not that dark or dirty and I'm only at 95k. I've read that these transmissions are solid so I'm hoping this isn't anything too major. If I'm not in traffic I really don't notice the issue, it's just really jumpy and jerks when quickly getting on and off the pedals. I was hoping maybe it was a mount or something minor, it's strange to me that it only happens in traffic. If I'm going from not moving and am able to accelerate freely, I don't have any issues. It's just in this specific scenario. Once again, thanks for the help with this.

 

If you ignore the maintenance interval on your 5AT then you can expect to have problems. Not having to change auto tranny fluid is a MYTH.

"Dark or dirty" is not why you change your auto tranny fluid, if you wait until it's that crapped up then you're basically asking fate to deliver you a broken transmission.

It sounds to me like you're experiencing auto "clutch chatter" (yes auto trannies have clutches) and that if you are able to get on the throttle better then line pressure engages the clutch packs faster. This typically exhibits itself as a rapid vibrating sensation when accelerating at a slower pace.

If you are feeling a very solid THUD when getting on the accelerator and another solid THUD when letting off (particularly when in manual shifting mode where the tranny is trying to slow the vehicle back down) then it's probably just a blown rear diff subframe bushing.

 

Thanks for the reply, I went to a nissan dealer near me today to try to figure it out. We went on a test drive and it was hard to replicate because it's only somewhat noticeable in heavy traffic. The tech scanned it with their consult tool and tried to figure it out but said nothing popped up and it was hard to diagnose. He couldn't tell what the problem was after the drive or the 1 hour diagnostic which was disappointing but I knew it was a possibility. However, I needed my trans fluid changed so I was hoping that would do the trick.

I had them do a drain and fill and then they discovered the trans pan had a slight leak so they replaced the pan and gasket as well. He said my trans fluid was a little low but I'm not sure if it was enough to cause the problem. I took a 30-40 minute drive after I left the dealer and it seemed to be shifting better and not jerking when in traffic. I'm wondering if maybe it was a combination of low and dirty fluid that was making the shifting weird in traffic. Do you think this could have been it?

I will know more after driving it the rest of the week as I'm sure I'll hit heavy traffic on my way home from school. I hope that if it was a blown bushing or something else they would've diagnosed that or saw it when he was under my car. I'm hoping it's fixed now, seemed to be normal when I drove today but it was a odd thing to replicate.

 

Typically if the rear differential bushing is blown, you will see fluid on the aluminum diff cover. The bushing is a viscous type, so its fluid filled & over time they leak or blow out.

 

I would assume that the Nissan techs would have hopefully noticed if the bushing was blown then. They only told me my trans pan was leaking which make the fluid a little low. I did a drain a fill, hopefully it fixed the issue.

 

The biggest reason for changing the transmission fluid is to remove all the particulates that end up floating around in the fluid. There isn't a real FILTER on these transmissions, it's just a screen large sediment type. As the transmission accumulates hours of wear the clutch packs wear and the material gets suspended in the fluid and continuously pumped around, those particulates change the FRICTION COEFFICIENT of the fluid which causes it to start having different shift characteristics, as well as all those little microscopic bits of clutch wearing away at all the internal thrust points (where fluid is sprayed at high pressure against something, like the torque converter impeller edges or corners inside the valve body) which accelerates wear because you also end up with microscopic bits of metal (steel will accumulate on the large magnets at the bottom of the drain pan, aluminum will not).

The reason for changing the fluid is to remove those contaminates, hydraulic oil has an incredibly long life if it weren't for those contaminates (think things like forklifts that aren't using internal clutches because there is no gears to shift) but in an auto transmission where you have multiple sets of clutch packs, multiple brake sleeves, that's a lot of wearable components that shed off material into the fluid. Gotta get that stuff out to maintain proper shift characteristics as well as the longevity of the entire unit.

I think fluid change interval is something like 30k miles, drain and fill only, which is about 4 quarts of the total volume.

 

One thing you can do is add a filter to the transmission cooler lines. I added one to the return side of the transmission cooler circuit on my G35. I bought two, the first one I ran about 1000 miles and replaced it with the other new one I bought. Some particulates fell/drained out of the filter I removed, some aluminum shavings. The one I use is Magnefine 5/16" inline filter, they're basically a small fuel filter but with a magnet and a bypass valve should the filter ever clog. At $26, they're cheap insurance in my opinion.
They are quite popular within the Honda/Acura community, as many of their transmissions don't have a pan, filter or screen to clean/replace at all. Not to mention, Honda's transmission longevity is horrific in years past (HUGE recalls), especially with the V6 equipped models.