MaximA VlaD

iTrader: (7)

Hi All,

I could use some help with this one. This I30 has a transmission model RE4F04B (non-VLSD?). I do not have a CEL. But the speedometer has been bouncing up to true speed and down to some arbitrary speed (about 10-30mph less, depending on speed - at 70+ it shows 40, at 35 it shows 20). I was reading that 4th gen. Maximas had problems with the speedo heads, but I have not seen enough info about I30s. I tried replacing the revolution sensor, and it did not fix the issue. I also drove with an OBD scan tool hooked up, and the vehicle speed was reporting about same as speedometer (not true speed). I would think that means the speed sensor is sending incorrect info, but after looking at FSM wiring diags it may be that the TCM is making the error, which is why r&r of the revolution sensor did not fix it. Also, I pulled the TCM codes and the only code is for the Throttle Position Sensor circuit. Could that be related? I had to adjust the TPS last year and tranny shifts fine, but the speedo was fine until now.

Could this be the speedo head? If so, can I replace it with one from an I30 with Traction Control? I have tried tightening the four screws in the back of the speedo head, but it did not improve. The tachometer is fine this whole time.

I would appreciate some insight from your experience. Thanks!!

MaximA VlaD

iTrader: (7)

Update: I was driving with the Actron scantool hooked up watching the graph for vehicle speed, and the speed jumped up to normal whenever I was above 40mph on both the speedometer and the scantool. I am not sure how the TCM and ECU report this speed, but if both speedo and OBD get the data via same link then this explains why scantool was getting same thing the speedo was getting. The speedo needle bounced up to normal speed and down to its erroneous speed before, but now it seems to only report correct speed whenever above 40mph or so. This doesn't appear to point to a bad connection or harness, so I am wondering if there is an electrical issue or the speedo is in fact known to be behaving like this. Any input from you is appreciated! thanks in advance.

MaximA VlaD

iTrader: (7)

From research I see that I am not the only one with 'speedometer needle jumping/indicating lower-than-true speed' problem, so I will post some info I have learned to help others even though there has been a lack of input from anyone in this thread.

The VSS sits in the tranny housing and reads the passing teeth of the reluctor ring inside, and if it is out of spec or the reluctor ring is warped/damaged/missing teeth/out of spec, it will give erratic info. If it was a wiring short/break the speedo would prob just quit. If one hooks up a graphing voltmeter directly to the sensor and drives or lets the wheels spin off the ground, they will see the erroneous info provided by the sensor.

My dilemma is how the reluctor/sensor came to be out of spec. Nothing was done to the tranny, except a fluid change a year prior to the issue. Could the fluid brand/quality have an effect on the reluctor ring? I would assume that is possible since some fluids have an effect on the synchros in manual transmissions.

MaximA VlaD

iTrader: (7)

I narrowed down this problem to the reluctor ring/wheel inside tranny.

The speedo readings were actually erratic bc the readings it was getting from the speed sensor were jumping. They were jumping bc of the reluctor ring possibly losing its magnetic qualities, which are necessary for the sensor to pick up the magnetic field and determine the rotation speed. Basically same principle as ABS.

Unfortunately for me there is no easy way to fix a "bad" reluctor wheel inside the tranny, and I am not quite sure how or why it went "de-magnetized". I was wondering if anyone has any input on this or had similar or same experience.

Thanks in advance, and I hope this helps someone someday too!