Thanks for the input Raj, but it wasn't during shifting; once the car began to operate normally and the rpm's climbed high enough to shift, it shifted fine. The bucking was when I first began to accelerate at about 10% throttle, still in first gear. I would get to about 2,000 RPM and then it would buck. This persisted for a while, and then the RPM's were able to climb higher and higher before bucking until the issue went away. I was able to get it into boost (w/g spring) a few times and all seemed normal. This happened both in AT mode and MM. As I said, the more the car was driven, the more the problem went away and the car began to drive like normal. No AT light came on.

The tranny was filled per the FSM like you pointed out in your 2nd point. When this first started to happen, we stopped and checked the fluid level and it was full. It took about 10 quarts.

 

Ok, that sounds like the torque converter then. Do you know if your installers put fluid into the converter before installing? I believe that's part of the FSM instructions - if you just fill up afterwards from the tranny, well - that's not good. It really does sound like the fluid finally made it's way to the TC....

Tell us how it does today and what SGP's feedback is. (fingers crossed that all is well now!)

EDIT: I noticed this is the first thing Sharif asked above - lol. Lots of little details that need to be addressed - easy to miss a step...

 

if it is a bucking, it sounds like the ckp sensor on the trans is rather dirty or damaged. i would take the ckp out and clean it and reinstall it. the ckp is really sensitive. we just had a car that had the same problem come in and the culprit was the ckp. if you have any other questions, give us a call at sgp, we'll take care of it.

thanks
johnny@sgpracing

 

ckp = crank position sensor? interested to know how this turns out...

 

Quick update...

1. Shop filled the tq converter before installation with 2 quarts and followed the FSM instructions on how to fill the tranny, as they have multiple times before for me.

2. We added an extra 2 quarts today, which comes out to 12 total...this should be just the right amount. The problem persistant and didn't really change. The bucking varied. Sometimes I could go WOT in 2nd gear, and buck in 3rd, and other times the other way around. There is no significant pattern of behavior of the trans.

3. The problem is only between 1k and 3k RPM and seems to get better the warmer the car is. Above 3k, the car pulls and shifts like a beast, chirping the tires on w/g spring.

4. Although my crank angle sensor was replaced during the fall, we're going to hopefully replace it tomorrow if Nissan gets it. The only code I get is "crank angle position sensor circuit A" after driving around for a while. I've had this code before with both blown trans and it didn't start happening until the trans was bucking in 3rd gear. When I replaced the original blown trans (the one SGP built), the used trans I put in fixed the crank sensor code issue. But, after a couple thousand miles, the trans began to buck and the code came back. The question is, which came first? The chicken or the egg?

SGP has been very helpful thus far in helping us diagnose the problem. I did not make this thread to blame anyone, only to get ideas and answers to questions I had. Thank you everyone for your help.

I will keep this thread updated. I know many of you are curious and I've recieved a lot of PM's.

 

So if I'm reading correctly, this is the 3rd time you're having a potential problem with the crank sensor? Wonder what could be the underlying cause? Three bad sensors seems unlikely...

 

Well, we don't kow if that's the issue. One thing I've learned during my entire process is that the CEL code isn't always correct . I am hoping that it is just the crank angle sensor, but you're right, what would cause it to go bad?

 

I found this while googling for info

 

So we replaced the ckp sensor and now the car barely starts...

anyone else have any ideas? does anyone know why Nissan would replace the cam sensors in the recall for the ckp sensor I posted above? I'm thinking about getting these as well just incase.

 

Just throwing this out there as i dont know.....but didnt aps have a problem with the ckp sensor and have to sheild the wiring to it.I know you have the greddy twins but im just trying to help.

 

yeah, someone pmed me the thread, but i believe it was ruled that it was only necessary if you ran the Unichip. I'm trying to contact Charles.

What I'm beginning to wonder now is if the ckp sensors are the same for Nissan and Infiniti and if I need to replace the cam sensors as well as per the recall notice. The P/N on the sensor (manufacturer part #) is identical except for 1 character and the P/N on the bag (Nissan part #) is exactly the same. I'm going to call Infiniti tomorrow and see if I can get a recall pack with the 2 cam sensors and ckp sensor.

 

They should all be the same part......and i say this cause i just had a throttle body fail and bought it at the infiniti dealer and it said nissan on the box as all the parts do.

 

You're right, the shop had Nissan cross-reference infiniti and they are the same parts. We're going to try some things in the morning and replace the cam sensors as part of the recall

 

Update:

I don't to write a novel, so I'm going to try to keep this as short as I can.

After I left the shop two weeks ago, the car would not keep an idle and had to be pushed in with a crankle angle sensor code. This is the day after we put the new trans in and the car was bucking horrendously in every gear.

The shop did the following (I know they did more, but I can't remember everything):

1. Ground the crank sensor wire to the chassis instead of the ECU
2. Redo most grounds to the chassis
3. Run a new shielded crank sensor wire
4. Replace crank sensors and cam sensors

After all was done, and the car was started, it took about 5 minutes for the idle to stabilize, but it did and idled better than ever. It's also started the quickest it's ever started. Everything seemed fine.

Curiously enough, the new crank sensor from Nissan, which was cross-referenced with Infiniti by Nissan to make sure it will work, caused the car to start, but there was no throttle. Even a minor blip of the throttle would cause the car to choke.

So, we put back my old sensor which we thought was bad and voila! Throttle was back and everything was all set.

The car drove well, except the bucking was still there, but not nearly as prevalent as it was before...

1st gear: no bucking
2nd gear: 50% bucking
3rd gear: 10% bucking
4th gear: 90% bucking
5th gear: 10% bucking

It seems like the even gears are the worst, and accelerating in the odd gears barely causes any bucking. We're going to see how the car does tomorrow, check fluids, etc. So far so good and it drives MUCH better than it did when I first drove out with the new trans. I couldn't even get it into 2nd gear, lol.

/novel

 

That is so bizarre. Did you ever get the opportunity to run through a diagnostic with the Consult II hooked up?

I've attached two images out of a FSM for a 2004.5 G35 5AT for diagnosis without any tools. Maybe it'll help you isolate the glitch. I'd consider trying a stock valve body to see if the issue resolves (if you haven't already).

Good luck!

 

Defective transmission? :\

 

Thanks man. We have all the service manuals, but I don't remember seeing the self AT diagnosis. Might give that a try.

It's very bizarre. We couldn't run a consult because the car wouldn't idle so no way to even get it to the dealer, lol. At least now the car is diveable and I can have a dealer run the scan tool

We're gettin there. It just takes patience and time.

 

We're trying to eliminate everything but the transmission first, going under the assumption that the trans is fine. So far it's been working out for us. We'll see how it goes.

 

How many miles are on the tranny with the new VB and internals? I remember when I put my built VB in it was shifting very hard and acting a little strange. I called another member that had the same thing done and said he went through the same thing. His went away after a couple days and so did mine. I know the tranny is a learning tranny so my guess is that it had to relearn all the shift points and pressures with the new VB. Now that you have the sensor issues figured out drive the car a little. Just cruise around in auto mode and let it go through some cycles.

 

This also happened to my trans after i bought your old vb but after about a 100 miles it worked fine and still shifts fast and hard.