4l60E VSS and reluctor ring giving boucing signal

[littlecars]

I am most of the way threw a motor conversion in my 85 toyota pickup but I have one problem I cant seem to get past.

The motor/tranny/pcm are from a 1998 s-10(originally 2wd). 4.3 V-6/4l60E. The back of the tranny has the tailhousing removed and a Advanced Adapter bolted up so I could mount the toyota transfere case behind it. The adapter between the tranny and transfere case has a VSS sencor.

The VSS sencor on the back of the tranny output shaft it putting out a "bouncing signal"!!!!! I know this becouse my OBD2 scanner shows me the speed the PCM "thinks" I am going based off of the VSS sencor.

It is reading fairly good at low speeds but when I accelerate the signal starts bouning. At 40 MPH cruising the VSS signal bounches between 16 MPH and 65 MPH. this couses the PCM to shift the tranny from 2nd, 3rd and forth gear, while I am trying to go a steady 40 MPH.

I replaced the VSS with a new one twice, I have adjusted the gap between the VSS and the reluctor ring about 10 times. I know the gap is not the problem. I have tried to adjust the "clocking" a few times with no luck. The reluctor ring is tight on the output shaft of the tranny. I dont know what is wrong.

I though about hooking up my multimeter to the wires on the VSS to look at the raw signal that the VSS is sending to the PCM, but I am not sure what I should be seeing. I assume it will be a AC voltage that goes up as I accelerate? any Idea what the voltage should be and what speed? and Ideas on how to test? could it be my PCM?

Any ideas?

[SSnow]

It's probably sending a pulsed DC signal (i.e. digital, on/off). A digital multimeter will see it change but not be quick enough to see it to count, especially at higher frequency. You would need a meter that can count frequency. This would help in trouble shooting as most will generate a frequency signal. Can your OBD II reader scan and record inputs to the ECM ( I know EFI Live and Autotap will). If so use it to see what is going on with the input.
Sorry I don't have a clear answer for you but it might get you in the right direction.

[littlecars]

Great information. I have a oscilloscope at work that I can use. It is a very complicated fluke, I bet I can figure it out though. I will have to give it a try. It will be a few days before I get a chance to use it. Any other ideas

[littlecars]

I hooked up the O scope last night. The VSS is giving a good stead digital pulse, but the voltage of the pulse is bouncing a little. Not a lot, just about 100 mV.

Could there be something in the programm that my programmer could have changed, to couse this problem?

[SSnow]

I hooked up the O scope last night. The VSS is giving a good stead digital pulse, but the voltage of the pulse is bouncing a little. Not a lot, just about 100 mV.

Could there be something in the programm that my programmer could have changed, to couse this problem?

Have you tried to change it back to see if the problem goes away?

[littlecars]

I dont do my own programming, I sent it to texas to speed scene wiring. I am just trying to prove every other compeonent before I sent id back to them.