Transmission problems

BEAU FORE

MEMBER
2007 NISSAN TITAN
5.6L
V8
4WD
AUTOMATIC
220,000 MILES

Bought this truck with bad transmission (knowingly) not shifting from 3-4 goes into neutral. Purchased a rebuilt transmission professionally installed and having the same problem. Speedometer has not worked and still is not working (replaced sensor). Currently have a new transmission on the way but my concern is the speedometer is causing all the problems (from research). Comments and or suggestions are greatly appreciated.

1 Reply

KASEKENNY

MECHANIC
18,907 POSTS

Hi Beau,

Before you replace the transmission again, you need to check and make sure there is a valid speed signal.

The speedometer (combination meter) gets the vehicle speed sent to it from the ABS and the ABS gets the speed from the wheel speed sensors. The fact that you don't have the speedometer tells me it is most likely not one of the sensors but one of the control modules. However, due to this being a CAN bus network, you cannot take simple voltage readings like you used to. You will need a scan tool and monitor whether the speed signal is being received by the ABS and then the combination meter.

Also, this could cause your shifting issue as well because the TCM needs vehicle speed to determine which gear is needed. If there is no valid vehicle speed signal then it will go into protection mode which appears to be N for this vehicle. Basically, it prevents the shift because it doesn't want to damage anything.

Let me know if you have a scan tool or can get access to one and then what the ABS says the vehicle speed is. There should be four wheel speed sensors and then one average speed of all four sensors.

Images (Click to make bigger)