i'm having issues with BLM's staying in 16,17,18 only, and i've narrowed it to the fact that it has no VSS input, thinking it is ideling all the time, or not in gear.

Does the VSS use a VR sensor producing a AC signal?

What is the minimum pulse per revolution that the PCM will see, when using TunerCAT to change that value

I want to use a general VR sensor close to the ears on the front universal join, creating 4 pulese per revolution

I dont need it to be accurate, just enought to let the PCM know if the vehicle is stopped or moving

any ideas or input?

 

Not having a VSS signal shouldn't be affecting the PCM going into closed loop. Think about it.... start it up and let it idle for 5 minutes. After the O2 sensors heat up, the coolant reaches 120-140degF and the timer passes 2-3 minutes, it goes into closed loop.

What program are you running in the PCM - M6 or A4? The M6 program is looking for 40 pulses per driveshaft revolution, the A4 program is looking for 17 pulses per DS rev. The signal is AC. "Jagsthatrun" has an extensive tech section on the output signals for the VSS sensor.

http://www.jagsthatrun.com/

Its also possible to run a reluctor ring and a VSS sensor from a mid-90's Chevy truck TH400 that will produce the correct signal. I have one on ny TH400. This has been discussed repeatedly on the "Drivetrain" forum. You might want to do a "search" there.

Finally, this doesn't belong on "LT1/LT4 Engine Tech"..... either "Computer....." or "Drivetrain"....... I'll move it to "Computer....."

 

You might want to try a search under my name. I have the same issue, TH400 and only 16.17 and 18 cells used. I posted a couple of years back about the situation, but never really resolved the issue. I, also, never bothered hooking up a speedo.

 

Ah, Not to challange "The Master" but I believe you've got it backward Fred

M6=17
A4=40

Steve

 

Overlooking the sarcasm ... yes, you are correct. 40 pulses per rev for the A4, 17 for the M6.

 

For those doing a TH400 install (or any other transmission w/o the proper VSS signal) in their 4th gen, you can use any of the ABS wheel speed sensors to get your VSS signal. Of course, the # of teeth on the ABS reluctor wheel is not going to be the same as the VSS reluctor wheel, but that is a minor change in LT1 edit/tuner cat.

Unfortunately this doesn't help those doing a TH400/LT1 retrofit in an early model car or truck that doesn't have ABS ...

 

damn where would i come up with a reluctor ring that will fit the 40 spline long output shaft on the TH400

 

mid 90s trucks before the 4l80e came out should have one that fits, even one from a 4l80e should fit from what I hear, again, never verified this, but might.

 

welp come to find out its got a 32 spline output so im gonna get the 90 model SS 454 th400 parts

 

Did you check out www.Jagsthatrun.com as Fred suggested? I think they can solve your problems pretty readily.