2005 350Z Enthusiast 6 spd.

I just changed final drive ratio to a 4.08 with a Z1 upgrade kit. With the TC engaged, I started having issues with the slip light and engine RPM cut out since doing the changeover. On occasion and under hard acceleration, the light flashes and the engine speed is cut. Doesn't seem to be able to be duplicated on the same road surface in the same area. Happens on a straight road and is random. Never know when it will happen.

The changeover was done by a Nissan master tech so I know it was done right but even he can't explain why this is happening. The car has been run with a Nissan diagnostic computer hooked up and all speed sensors check out OK but with a 1, and on occasion, a 2 mile per hour front to back difference when the issue does arise. Physical inspection of the sensors reveals no issues.

Tires are 245/35/19 front and 275/35/19 rear, which seems to be a common tire upgrade, a 0.8" stagger. Never a problem before the ratio change and these tires are within the tolerances for the TC suggested in this 350Z forum. Anyone have any ideas?

 

It's possible the system is working as designed. Your new rear end will result in more torque being applied to the rear wheels in every gear, making it easier to get excessive rear wheel slip.

 

Thanks for your response. There is no indication that the wheels are spinning or even a slight slip. The slip light flashing and RPM cut comes in the middle of an acceleration pull, not in the beginning of the pull. I would like to think that my car is powerful enough to spin the tires in 3rd gear @ 50 MPH with 71R 275/35/19 rear tires, but I know that isn't the case :--). Wish it was that simple :--).

 

Are your tires evenly worn or are your rears newer than your fronts? I had an issue with the slip light when I replaced the rear tires. Stock sized.

The gear ratio I wouldnt think would make a difference the sensors are mounted on the side of the diff and they go off those little grooves in the axles, unless the computer system takes into consideration the transmission speed to wheel speed (which I dont think it does) changing the final drive shouldn't cause this problem.

Could your harness be coming loose at times or any of your axle grooves been messed up during the installation?

Sucks to spend all that money then have problems, good luck.

 

The tires are 71Rs and all four have been on the car for a little less then a year now. Multiple track days but no unusual wear is evident. All visible parts of the TC system, sensors, connecting wires and the splined axle rotating units have been checked and again, nothing unusual found. I don't think the computer enters this picture either and the Tech, who only works on Zs and GTRs, would have mentioned that possibility. He is as frustrated about this issue as I am. His only comment is about the tires with that 0.8 inch stagger.

A 1 inch stagger is the max according to other posts on this forum so I should be alright, but of course, that is not the case :--(. I'm close to the limit but everything was OK before the gear ratio change. I keep thinking there is a simple solution/answer staring right back at us but it alludes us right now.

Thanks for your response. Hoping to get to a solution soon :--)

 

i say install stock tires/wheels and give it a try...
you had the same tires before installing your FD ?

 

Can't do that or I would've done that as soon as the issue became apparent. The car has a Akebono BBK on it and the 17 inch wheels will no longer fit. No issues were there with the tire/wheel combination before the gear change. The gear set was the only change. As an added bit of information, no fault codes have surfaced.

Thanks anyway for your thoughts.