VSS for PCM when using a TH350
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TECH Apprentice
Joined: Oct 2013
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From: Longview, TX
VSS for PCM when using a TH350 I am planning to run a TH350 behind my LM7 in my swap, mainly because I have it and it is ready to go.
I understand that the PCM needs a speed signal usually from the VSS in the transmission. Since the TH350 does not have a VSS, HOW do I get that signal to the PCM?
OR is that signal really needed? The truck will be more of a toy and not a daily driver, but will be driven to work on occasion.
I understand that the PCM needs a speed signal usually from the VSS in the transmission. Since the TH350 does not have a VSS, HOW do I get that signal to the PCM?
OR is that signal really needed? The truck will be more of a toy and not a daily driver, but will be driven to work on occasion.
A stock PCM will use the VSS as part of adjusting certain parameters. Mainly for certain IAC setting. On the GMPP harness (E67 ECU) that I am using in the GTO, the VSS is listed as being optional. Having said that, on occasion, when I come to a stop after a prolonged period of driving, like taking an exit off the highway, the engine will die when I put the clutch in and coast to a stop.
Andrew
Andrew
Thread Starter
TECH Apprentice
Joined: Oct 2013
Posts: 319
Likes: 4
From: Longview, TX
A stock PCM will use the VSS as part of adjusting certain parameters. Mainly for certain IAC setting. On the GMPP harness (E67 ECU) that I am using in the GTO, the VSS is listed as being optional. Having said that, on occasion, when I come to a stop after a prolonged period of driving, like taking an exit off the highway, the engine will die when I put the clutch in and coast to a stop.
Andrew
Andrew
Dakota Digital makes a 8K pulse generator that is a pass through that can run my mechanical speedo too. That might be what I need to do.
SEN-01-4160 - 8K pass-through pulse generator with adaptor cable for GM transmissions with cable drive speed output.
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The Dakota digital pass thru VSS WILL prevent stalling issues, at least with manual trans.
The ecu does not need to be tuned to the correct speed.
I have 2 conversions that had the exact symptoms above. The DD VSS cured it.
The ecu does not need to be tuned to the correct speed.
I have 2 conversions that had the exact symptoms above. The DD VSS cured it.
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Verdad Gallardo Thread Starter
TECH Apprentice
Joined: Oct 2013
Posts: 319
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From: Longview, TX
Looks like the DD sensor is the one I need. I found this one too on ebay, but not sure it is a pass thru to allow me to keep my mechanical drive speedo.
http://www.ebay.com/itm/351945485671?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
http://www.ebay.com/itm/351945485671?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
One other note, the DD VSS sticks out quite a ways from the trans, the one above looks as large. If you don't have clearance, you'll need a short extension speedo cable that DD has but doesn't list on their website.
What kind of vehicle are you swapping?
Im in the middle of a early 90s ford vehicle with rear abs, i tied the vss into the rear abs speed sensor in my diff. It works also, spinning it as fast as i could it showed max of 5 mph on my tech2 and then slowed back down correctly. It seems pretty accurate even tho idt it has to be. (I have mechanical speedo also) like some1 said previously pcm just need to see a signal that car is or isnot moving. Hptuners can adjust this also and get it closer.
If you have an older vehicle without abs then this wont help you. But i think it is interesting that it seems to work lol
Im in the middle of a early 90s ford vehicle with rear abs, i tied the vss into the rear abs speed sensor in my diff. It works also, spinning it as fast as i could it showed max of 5 mph on my tech2 and then slowed back down correctly. It seems pretty accurate even tho idt it has to be. (I have mechanical speedo also) like some1 said previously pcm just need to see a signal that car is or isnot moving. Hptuners can adjust this also and get it closer.
If you have an older vehicle without abs then this wont help you. But i think it is interesting that it seems to work lol
My e38 ecm will not directly read the Dakota digital vss I installed on my th400 because it is expecting an automatic Tcm to read the vss and send the signal over can bus. Some people have gotten it to work but my tuner tried a number of settings without luck. With a th400 I have so far seen no ill effects but I also have less than 200 miles on the car since swap.
My e38 ecm will not directly read the Dakota digital vss I installed on my th400 because it is expecting an automatic Tcm to read the vss and send the signal over can bus. Some people have gotten it to work but my tuner tried a number of settings without luck. With a th400 I have so far seen no ill effects but I also have less than 200 miles on the car since swap.
I know on the T56/LS3 Corvette set ups, the VSS sensor is a 2-wire (sine wave) VR device -- magnet stationary/ferrous trigger moving - toothed wheel in tranny, not a Hall-effect sensor (pickup stationary, magnet moving). Any conversion to a square wave signal that might be needed (for example by a speedo) occurs, I think, in the ECU. Can anyone confirm whether or not the factory speedos need a square wave vs a sine wave signal? I know the Corvette ECU is looking for a sine wave signal, not a square wave.
I made a multi-tooth reluctor to be mounted on the rear pinion flange and positioned a stock T56 VSS sensor on the rear end to read that reluctor. Works just fine for the ECU's purposes. However, Dakota Digital urged me to use their cruise control set up designed to receive a simple sine wave/Hall effect signal generated by two magnets on the driveshaft. So my cruise input and my ecu input are provided by two different sources. Drivability and cruise function are both flawless.
To the OP - I'd create something that mimics the VSS in whatever tranny came behind the ECU you're running. The ECU will get the speed signal it's expecting.
I made a multi-tooth reluctor to be mounted on the rear pinion flange and positioned a stock T56 VSS sensor on the rear end to read that reluctor. Works just fine for the ECU's purposes. However, Dakota Digital urged me to use their cruise control set up designed to receive a simple sine wave/Hall effect signal generated by two magnets on the driveshaft. So my cruise input and my ecu input are provided by two different sources. Drivability and cruise function are both flawless.
To the OP - I'd create something that mimics the VSS in whatever tranny came behind the ECU you're running. The ECU will get the speed signal it's expecting.
My e67 ECU that I have as part of the GMPP harness kit is definitely looking for a sine wave (VR type, 2 wire) sensor. I've never seen any OEM GM computer was a 3 wire sensor...
Andrew
Andrew