Can anyone explain OSS, VSS, and TSS?
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5th Wheeling
Joined: Sep 2004
Posts: 25
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Can anyone explain OSS, VSS, and TSS?
What is the differences between these three sensors? They seem to all live on the trans and all feed the PCM info. What I can't determine is for what, what type of signal, etc.
I have a 2003 E350, 5.4, 4r100
That isn't even getting into the differential speed sensor. lol
I am lost but trying to figure this out for a future swap.
Thanks in advance if you can explain like I am 5
I have a 2003 E350, 5.4, 4r100
That isn't even getting into the differential speed sensor. lol
I am lost but trying to figure this out for a future swap.
Thanks in advance if you can explain like I am 5
Frmr Ford Trans Engr
Joined: Aug 1999
Posts: 24,714
Likes: 2,640
From: SE Florida
TSS is the Turbine Speed Sensor. It measures the speed of the torque converter turbine, which is also the transmission input shaft speed. It is located towards the front of the trans, on top.
OSS is the Output Speed Sensor. It measures the speed of the output shaft of the transmission. It is located at the back of the trans, on top.
VSS is the Vehicle Speed Sensor. It measures the rear differential ring gear speed. This is used to calculate vehicle speed for the PCM (Powertrain Control Module,) the speedometer, and the odometer.
The PCM calculates transmission gear ratio by dividing TSS by OSS. This is used to control the shift quality.
OSS is the Output Speed Sensor. It measures the speed of the output shaft of the transmission. It is located at the back of the trans, on top.
VSS is the Vehicle Speed Sensor. It measures the rear differential ring gear speed. This is used to calculate vehicle speed for the PCM (Powertrain Control Module,) the speedometer, and the odometer.
The PCM calculates transmission gear ratio by dividing TSS by OSS. This is used to control the shift quality.
Last edited by Mark Kovalsky; Apr 26, 2026 at 08:59 AM.
Thread Starter
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5th Wheeling
Joined: Sep 2004
Posts: 25
Likes: 0
TSS is the Turbine Speed Sensor. It measures the speed of the torque converter turbine, which is also the transmission input shaft speed. It is located towards the front of the trans, on top.
OSS is the Output Speed Sensor. It measures the speed of the output shaft of the transmission. It is located at the back of the trans, on top.
VSS is the Vehicle Speed Sensor. It measures the rear differential ring gear speed. This is used to calculate vehicle speed for the PCM (Powertrain Control Module,) the speedometer, and the odometer.
The PCM calculates transmission gear ratio by dividing TSS by OSS. This is used to control the shift quality.
OSS is the Output Speed Sensor. It measures the speed of the output shaft of the transmission. It is located at the back of the trans, on top.
VSS is the Vehicle Speed Sensor. It measures the rear differential ring gear speed. This is used to calculate vehicle speed for the PCM (Powertrain Control Module,) the speedometer, and the odometer.
The PCM calculates transmission gear ratio by dividing TSS by OSS. This is used to control the shift quality.
Mark, why does it say in the FSM that the VSS is diesel only? That is what was screwing me up and getting me confused
Also, my goal here is to remove the 4r100 and replace it with the 8hp70. Obviously this is going to cause issues with the PCM not getting trans info. I was hoping that the addition of the VSS from the 8hp70 converted to VS from the Hall Effect via a Dakota Digital convertor would make the PCM happy for the engine needs. Any thoughts on my idea? Possible or I am an idiot?
Frmr Ford Trans Engr
Joined: Aug 1999
Posts: 24,714
Likes: 2,640
From: SE Florida
Also, my goal here is to remove the 4r100 and replace it with the 8hp70. Obviously this is going to cause issues with the PCM not getting trans info. I was hoping that the addition of the VSS from the 8hp70 converted to VS from the Hall Effect via a Dakota Digital convertor would make the PCM happy for the engine needs. Any thoughts on my idea? Possible or I am an idiot?
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