4l80e vss and iss

[Scooterwrench]

no. drac uses a 40 tooth wheel usually in tail shaft or transfer case

And reads what?,the driveshaft!

 

[tayto]

nice try, but no

 

[eran tomer]

so if the vss is on the transfer case, the plug that I got in the harness doesn't fit. the 2 sensors are different. is there an adaptor for it?

 

[NickTransmissions]

And reads what?,the driveshaft!

Speed sensors are hall effect devices that read/interact with "reluctors" and produce output voltage via magnetic field. That voltage data stream is continuously read and converted to actionable/applyable information by the vehicle's pcm and used to manage the powertrain and provide output data for your display by your dash speedometer, etc.

Anything can serve as the reluctor as long as it's made of ferrous metal that the magnetic speed sensor can interact with and produce a magnetic field. This includes (but is not limited to) purpose built "gears or wheels" splined and/or pressed-on to shafts (many transmissions like the 4L60e as well as tcases, like @tayto mentioned), drums, planetary carrier assemblies (4L80e rear planet), cast steel drums with lugged sections around part or all of the drum's OD that rotates under the sensor (4l80e forward drum) or even ring gear "baskets" with cut-outs that serve has hall effect pick up points for sensors (gm 6L/ford 6R transmissions as two examples).

The driveshaft is simply spinning at the same speed as the shaft that hosts the reluctor (in all cases for VSS, the trans or tcase output shaft) so I can see why you'd think the sensor reads the driveshaft directly if you're not familiar with the hall effect principal and role it plays in sensor strategy and powertrain control/management.

Note that this is a laymen's terms explanation as im not an engineer.

 

[Scooterwrench]

Speed sensors are hall effect devices that read/interact with "reluctors" and produce output voltage via magnetic field. That voltage data stream is continuously read and converted to actionable/applyable information by the vehicle's pcm and used to manage the powertrain and provide output data for your display by your dash speedometer, etc.

Anything can serve as the reluctor as long as it's made of ferrous metal that the magnetic speed sensor can interact with and produce a magnetic field. This includes (but is not limited to) purpose built "gears or wheels" splined and/or pressed-on to shafts (many transmissions like the 4L60e as well as tcases, like @tayto mentioned), drums, planetary carrier assemblies (4L80e rear planet), cast steel drums with lugged sections around part or all of the drum's OD that rotates under the sensor (4l80e forward drum) or even ring gear "baskets" with cut-outs that serve has hall effect pick up points for sensors (gm 6L/ford 6R transmissions as two examples).

The driveshaft is simply spinning at the same speed as the shaft that hosts the reluctor (in all cases for VSS, the trans or tcase output shaft) so I can see why you'd think the sensor reads the driveshaft directly if you're not familiar with the hall effect principal and role it plays in sensor strategy and powertrain control/management.

Note that this is a laymen's terms explanation as im not an engineer.

Harley uses a hall effect sensor(three wire) to read one of the gears in the trans but these trucks use a magnetic pick up(two wire) and a magnetized reluctor wheel,at least that is what's shown in the manual.
I was just simplifying the statement that the tail shaft sensor is reading the driveshaft RPM off the tail shaft VSS,not actually reading the drive shaft itself. Laymans terms works for me!

 

[yevgenievich]

Early on gm did use all three speed sensors with 4l80e set up. I believe diagnostic type logic referenced input/output sensors while tcase sensor was used for rest