VSS and Transmission Output speed

[Shannen Durphey]

Peter D. Hipson wrote:
> 
> I'm doing extensive work on the TISS/TOSS senders. No, they are not equal
> in pulses per revolution, there is a substantial difference. (I've the
> ratios, if that's important...)

Sure, pass 'em along for posterity's sake.

> The senders are both magnetic coil type,
> returning an A/C signal who's frequency (and voltage) varies with the RPM.
> The only reason the voltage changes is due to improved efficiency at higher
> speeds--the voltage change is not significant to the TCM, for example. Be
> aware that common mode noise can be a problem with these senders, as can
> bad connectors. As well, the sender itself fails frequently--arrggg! <g>
> 
I think I remember reading or hearing that the VSS signal voltage can
get extremely high before conditioning.  What voltage levels are you
seeing on average and how high do they peak?
Shannen 

> At 11:01 PM 3/11/99 -0500, you wrote:
> >Hi, Dr. Plecan.
> >
> >4L80E trans has 2 speed sensors installed, Transmission Input Shaft
> >Speed and Transmission Output Shaft Speed.  Early 4wd (pre94) had
> >separate VSS and dedicated signal to PCM, 2wd and 94+4wd didn't have
> >extra sensor so combined the signals.
> >
> >TOSS is used for gear ratio calculations, VSS is used for shift
> >control.  TISS is used for TCC control, shift pattern, shift quality.
> >
> >I remember a few codes for these, trans component slipping, tcc apply
> >error, undefined gear ratio, excessive shift times.
> >
> >Nothing I have gives # of pulses/rev, but I think the frequency is
> >different between the two shafts, due to different "wheel" diameters.
> >Definitely A/C from the sensor, as they are the same part no.  TISS
> >must be conditioned inside the PCM, TOSS may depend on the year of the
> >calibration.  Kinda makes the electronic
> >simulations a job for the entire CSH staff...
> >Shannen
> >
> >Bruce Plecan wrote:
> >>
> >> On a 8625 pcm, there are two connections, one labeled VSS, which is vehicle
> >> speed sensor, and a second one labeled transmission output speed,   they
> >> both feed from the Vehicle Speed Signal Bufffer to the PCM.  Can anyone
> >> splain this to me?.  Is this just a way of checking for transmission
> >> "slippage".
> >> Anyone happen to know what this 5v signal should be?.  ie square,
> 4,000ppm?.
> >> Thanks
> >> Bruce
> >
> >
> >
> Thanks,
>         Peter Hipson (founder, NEHOG)
>         1995 White NA Hummer Wagon