I have a 2006 G35 with 103000 miles and the 5AT. When I accelerate, no matter how hard I push the car, I get a mild shudder/vibration in the whole car when the speed of the car hits approximately 20 mph. The slight vibration only lasts until about 25 mph and then the car is smooth throughout the rest of the rev range and speeds.

- Seems to happen independently of the gear that I am in.
- I read all about the 40mph transmission shudder and this is not violent enough to qualify.
- If you are on a rough road, you won't feel it, it is that subtle. But it drives me nuts!
- Took it to a transmission specialist and after a test drive he suggested that it was not the transmission but rather something in the suspension, wheels etc.
- Car has new tires and the alignment seems fine when driving.

I have been searching this forum and have not had any luck. If I am missing an obvious post, please let me know and then a moderator can delete this thread.

thanks.

 

I had the same issue on my 06 at 15k miles. It was much more obvious going up inclines. I read about the transmission shudder and took it in shortly after. They replaced the valvebody with an updated part number and I have not had the issue since the repair. I am not suggesting this is your issue but it sounds the same as my symptons.

 

Sounds like the valve body to me, I don't have the same generation G but they have repalced mine twice. They just lumped it under your model tsb so I was happy. It was so annoying.

 

I did a little more experimenting with the way I drive to see if I could diagnose the problem further. Below is what I tried and found.

1. I put the transmission in manual mode and no matter which gear I was in the shudder was at the same mph.

2. I tried different acceleration rates and it always happened at the same mph BUT it was much more pronounced at harder acceleration.

3. I tried coasting through the 20-25 mph range and it did NOT shudder.

4. I revved the engine without it in gear and had no shudder (eliminated engine balance issues)

Could it possible be an issue with the rear differential?

I plan to perform a tranny drain an refill this weekend using the video I found on the DIY thread. Nissan dealership wants $160 for a drain and fill and $400 for a flush.

This one has me stumped and it is annoying the crap out of me.

 

Universal joints? With that many miles on them, the needle bearings inside the caps tend to wear out flat. I had this happen to two other cars with high miles on them. If you have any experience under the car, changing out u-joints shouldn't be too difficult. Never done it on this car.

 

Great suggestion! I wonder if I get under there if I will be able to feel some play in the joints? In the other cars that you had problems with, was there much play in the drive shaft?

 

No, what happens is those flat, worn needle bearings don't like to rotate smoothly. So when they bind for that moment, it forces the driveshaft to wobble, if you will. The wobble is what you're feeling. They just tend to grab at the speed you listed. Mine did it around 45-50. Kinda faded in and faded out. Then it got noticeable again at triple digit speeds. Don't ask me how I got an '87 T-bird with a V-6 over 100.

 

I took the car in last Friday to my mechanic and he confirmed that my problems were not in the transmission. He dropped the drive shaft to find the needle bearings in the u-joints were in fact warn considerably and binding (not turning smoothly). The problem is that I have to replace the entire drive shaft as a unit rather than just the bearings. That is going to set me back $1000. I get the car back Thursday and I will update this post again to see if this fixed the problem.

 

could be a wheel bearing starting to fail,
some loosening bushings check things out

 

Did I call it or what? I didn't know the u-joints weren't replaceable though. Total bummer. Mental note on that.

 

I meant to update this a while ago, but the new drive shaft fixed the problem.