MSgpio.com read only forums (Jan.15,2018)

All,

It was mentioned at the Calgary MegaMeet this weekend that for a 4L60E equipped vehicle, a given vehicle speed sensor output frequency means different road speeds depending on whether you are in 4-wheel drive or not. We can use an input to tell the processor to adjust the computed speed based on the number of driven axles. However, to do this properly, we need more specs on the VSS (how it changes it output from 4WD to 2WD, etc.), any switches, etc. that are already in the system that we could interface MegaShift to. If anyone could post more info, I would appreciated it!

Lance.

I could be all wet here but the 4L60E only uses 1 VSS at any time in 2WD it's in the tail shaft housing ,4WD it's in the transfer case tail shaft housing. With a 4WD it would not matter where the range selector is ,the VSS will read the tail shaft speed.

Here is some info on 4L60E VSS
1. The two-pulse (2000 pulses per mile) square wave (D.C current or direct current) used on all TBI engines thru 1992, all computer-controlled-carbureted engines, and on 1985-1989 TPI engines.
2. A four-pulse (4000 pulses per mile) sine-wave (A.C. current or alternating current) signal is required by the 1990-1993 TPI, 1992-1993 LT1 engines, and 1990-1993 Camaro 3.1/3.4 V6 engines.
3. A 40 pulse per driveshaft revolution speed sensor used on 1993 and newer trucks with automatic transmission, 1994 and newer rear drive cars with the automatic transmission.

The 4L80E on the other hand has 2 VSS in 2WD and 3 in 4WD, in 4Wd this trans would need something to get the signal from the transfer case VSS

dch,

Ah, okay, that's why I hadn't heard about it. The person I spoke with must have been referring to the 4L80E. I knew these had 2 VR sensors, one on the input shaft and one on the output shaft. So for the 4L80E the VSS must be read from the transfer case in 4WD, otherwise it is read from the output shaft (in 2WD)? Is there an electrical signal sent to tell the ECU that the transfer case is activated (so the other VSS can be used)?

Thanks for the info, it really helps!

Lance.

Lance wrote: Is there an electrical signal sent to tell the ECU that the transfer case is activated (so the other VSS can be used)?

Yes,

The transfer case control module sends a signal to the PCM to indicate 4WD Low. When the TCCM tells the PCM that the transfer case is in low the PCM adjusts the shift points. I'm not sure if the actual speed signal changes sources(I don't think it does) but a multiplier is added for the T-case gear reduction.

Joe

Thanks Joe!

Anyone happen to know if this signal to the ECU is 5V or 12V, or does the ECU supply the pull-up and it is grounded (this matters for how to build the circuit), and whether 'high' or 'low' indicates 4WD (this matters for setting up the defaults)?

Lance.

Lance,

I will attempt to confirm this in the next couple of days but from memory it's batt V(12v) supplied from the PCM to the TCCM.

12v is supplied from the PCM to the TCCM. When the TCCM pulls low it indicates 4WD LOW.


Again from memory- The signals should be the same for manual 4wd and NP8 (Push button)

Give me a couple of days and I'll post what I find.

Additional note: I'll look into the 2 vs 3 speed sensors. If I recall this is also an early vs late year issue. I think the late model 4WD only uses 2 sensors. I think the outputshaft sensor is not used, only the t-case .

Joe-

Lance,

This is an example of a 2000 K1 4L60E

Joe-

Joe,

Thanks, that's perfect! I will add the 2WD/4WD switch to the code (likely on PE1/GPI1/Amp5).

Lance.

Lance,

The 4WD low circuit seems very consistent over the years and models I had a chance to check.

The push button 4WD uses the TCCM to pull the PCM signal low for 4WD low shift points.
The manual shift 4WD low just has a switch on the T-case that pulls the circuit low.

I checked multiple platforms and t-case setups and did not find an exception. I'm sure they are out there and will surface but I think that circuit will handle most of them.

Joe

Thanks Joe! It helps to have the confirmation from someone who knows.

The code includes the 4WD speedo switching now, but I need to finish a production board to test it (doing that as soon as I finish this post!). All testing from this point on will be with the production boards.

Lance.