Chevy Trailblazer SS Forum banner

1 - 20 of 37 Posts

·
Registered
TrailblazerSS
Joined
·
20 Posts
Discussion Starter · #1 ·
I have been searching for awhile and maybe I am not getting the words right or something so sorry to ask (if a simple bs question) Like the title states, I have converted from AWD to RWD, added a Circle D 3200 stall with a new GM VSS sensor. I have searched and searched and found some things to try out but nothing works so far, maybe the sensor is crap and needs swapped. I have tested ohms on it, and it seems within what I could find as spec, but was dirty upon arrival from Amazon. The wiring looks good, harness looks good. I compared ohms to AWD sensor and not even close to the same (different design of sensor with one mag pickup compared to two) but that might have no bearing on anything.

I did fill stall with fluid, and trans has good fluid in it now, truck runs great just cant get out of 1st nor am I getting any speedo responses. I have already ordered another sensor and will report back if that does anything, just wanted to see what you guys thought is all.

Side note do I really need to use that extension wiring from the AWD at all near the trans xmember? Or plug just the PCM harness 2 wire plug straight into VSS on tail shaft housing like a normal 2wd TBSS?

Thanks anyone who responds,

RObert
 

·
Lighter-than-you
TrailblazerSS
Joined
·
372 Posts
Not sure why they have ext harness for the AWD when it makes the distance without it, but no you don't need to have the extension there. The VSS sensor being bad would explain the speedo not working, but not the trans shifting, (or at least it shouldn't). AWD or RWD, although diff sensor designs, they give the same signal out. I've been through every last circuit on these and can't fathom why a bad VSS would cause it not to shift. I'm hoping the new sensor fixes everything for you, but if it does then I'm going to need to figure out why.
 

·
Registered
TrailblazerSS
Joined
·
20 Posts
Discussion Starter · #3 · (Edited)
Thank you for the reply. I read in the common faults for our trans on this forum that the trans will not shift nor allow speedo/cruise cont functions without it. Hopefully thats true (sadly hoping for that). I will follow up with ohm tests from original AWD sensor, first RWD sensor, and then replacement sensor numbers. I think the extension is there to wrap around the transfer case as the stock length harness barely reaches the RWD sensor. If this even helps, just wanted to get the info out if it helps for someone later on.

Also for future reference, my TCM was tuned as well. Also added was a Sonnax hardened output shaft and shift kit while the RWD conv was done. All new GM parts were used for mount, tail shaft housing and allegedly sensor. Just a little added info.
 

·
Lighter-than-you
TrailblazerSS
Joined
·
372 Posts
Oh yeah, definitely need it for cruise functioning. Not sure if it makes a difference or not, but the trans wiring is slightly different between 06-07 and the 08-09. What year is yours?

And thanks for trying to make it easier for members that might run into a similar issue.
 

·
Registered
TrailblazerSS
Joined
·
20 Posts
Discussion Starter · #5 ·
Mine is a 07 AWD initially. The strange thing about the "extension" harness is it looks to take off and run back to the engine bay along the drivers frame rail. Maybe I do need to use this for some reason, or perhaps it just wraps around inside the sheathing and doesn't really go up front? Either way I will be using the harness on the trans only once the new sensor arrives first, then Ill try the extension piece if need be. VSS should be here today so I will report back with findings of sensor ohms, and or overall function of the newer sensor.
 

·
Lighter-than-you
TrailblazerSS
Joined
·
372 Posts
just checked my factory RWD, all wires for the trans, vss and o2 sensors routes up and runs along top of trans, then top of engine, then down the side of engine and into tcm,ecm, fuse block. there isn't a factory ext harness there for VSS
 

·
Registered
TrailblazerSS
Joined
·
18 Posts
Not sure why they have ext harness for the AWD when it makes the distance without it, but no you don't need to have the extension there. The VSS sensor being bad would explain the speedo not working, but not the trans shifting, (or at least it shouldn't). AWD or RWD, although diff sensor designs, they give the same signal out. I've been through every last circuit on these and can't fathom why a bad VSS would cause it not to shift. I'm hoping the new sensor fixes everything for you, but if it does then I'm going to need to figure out why.
yes...it certainly will
The pcm used throttle position and speed to select gear change timing. Without knowing speed...it's not going to shift/behave properly
You don't need to go through the circuits...you need to know how the software in the pcm populates and uses the shift scheduling tables
 

·
Registered
TrailblazerSS
Joined
·
20 Posts
Discussion Starter · #8 ·
Thank you for jumping in and verifying things for me to be sure. Flomax, yes I had a friend in Vegas verify this for me as well. Its how I figured out it must be an extension just to get around the transfer case ONLY. Hopefully getting off work soon to try this sensor out. Damn year long (almost) build comes down to electronics haha.
 

·
Registered
TrailblazerSS
Joined
·
20 Posts
Discussion Starter · #9 ·
So new sensor, no dice. No speedo still no trans control, stuck in first. So because of photobucket I cant seem to find any damn wiring diagrams for the VSS on this trans. I found a 4L60 diagram that shows VSS as GN/BK as ground but I cant seem to get continuity on ground anywhere with this. Is this wrong? Should I be able to pick up a circuit touching a good ground on the vehicle from this side of things?
This sensor runs all the way to pin 16 on the TCM correct? Or does it stop somewhere else along the way?
 

·
Lighter-than-you
TrailblazerSS
Joined
·
372 Posts
yes...it certainly will
The pcm used throttle position and speed to select gear change timing. Without knowing speed...it's not going to shift/behave properly
You don't need to go through the circuits...you need to know how the software in the pcm populates and uses the shift scheduling tables
Thanks for correcting my misinformation. Now, Is this how all production 4l60/4l80 tcm's work the shift scheduling? Do aftermarket 4l60/4l80 trans need a vss as well?
One other thing I've been getting mixed info on is whether or not you have to have a PRND sensor? Or is it just for the PRND dash display? I know in the 08-09 that the sensor is inside the trans itself. Why didnt GM just do it that way to begin with instead of the over-complicated external sensor up until 07. No wonder I love the Turbo400 so much lol
 

·
Lighter-than-you
TrailblazerSS
Joined
·
372 Posts
So new sensor, no dice. No speedo still no trans control, stuck in first. So because of photobucket I cant seem to find any damn wiring diagrams for the VSS on this trans. I found a 4L60 diagram that shows VSS as GN/BK as ground but I cant seem to get continuity on ground anywhere with this. Is this wrong? Should I be able to pick up a circuit touching a good ground on the vehicle from this side of things?
This sensor runs all the way to pin 16 on the TCM correct? Or does it stop somewhere else along the way?
Damn, sorry man, this is suckin.. Let me check my harness..
Use this to fix all the blurry photobucket issues:
 

·
Registered
TrailblazerSS
Joined
·
20 Posts
Discussion Starter · #12 · (Edited)
So shot wires from VSS to TCM, all good there as well. PU/WH goes to pin 41 on TCM and L-GN/BK goes to 16.

I don't know where to go now with this haha. I doubt there are any fuses at play here. Any ideas anyone?

BTW thanks to the both of you for helping out.

Pins look seated well on harness and TCM itself. Nothing backed away or sunk in to plug.
 

·
Lighter-than-you
TrailblazerSS
Joined
·
372 Posts
You already checked fuse 15 right?
 

·
Registered
TrailblazerSS
Joined
·
20 Posts
Discussion Starter · #14 ·
Up front, yes its good. Thanks for adding that though. Rechecked all pins on PCM side as well (making sure from e fan install) all looks good here, seated correctly nothing pushed away from PCM in plugs.
 

·
Lighter-than-you
TrailblazerSS
Joined
·
372 Posts
The only things left are a bad ground somewhere (doubtful as it would affect more than speedo and trans) or the tcm itself, which also makes no sense bc the tcm was working fine b4 conversion i'm assuming.
 

·
Lighter-than-you
TrailblazerSS
Joined
·
372 Posts
Did you take apart the 4l60 and convert it to rwd or just got a rwd 4l60? If you did get a new trans for it, did you verify its for an 07 or earlier?
 

·
Registered
TrailblazerSS
Joined
·
20 Posts
Discussion Starter · #17 ·
This is my 2007 4L70e from my TBSS. The kit was installed (1.5 hrs away) locally and converted to RWD using the Sonnax hardened shaft and GM tail housing. The TCM was tuned by PCMofNC for my stall and I let them know the shift kit pieces going in.

Could the new output shaft not have the proper pickup placement for the VSS? The ground is a good question, as so much BS was taken apart over a long period of time. I have reseated the main plug on the trans again and looked it as well, looks pretty good. The arrow goes outboard or inboard on the trans main plug (mine is facing outward).
 

·
Lighter-than-you
TrailblazerSS
Joined
·
372 Posts
just more ideas.. input speed reluctor bad or mishandled..
reluctor gear on output shaft could be messed up or wrong part (for 4l60 non-electronic)
not sure how well you trust trans shop but maybe they didn't use yours or got them mixed up with other customers
PCMNC is really on top of their tuning but sometimes shit happens to the most reputable companies.. possibly one little tuning error causing all this, doubtful but gotta cover all bases now
 

·
Lighter-than-you
TrailblazerSS
Joined
·
372 Posts
check to see if you have power going into fuse 15
and you have no codes at all right?
 

·
Registered
TrailblazerSS
Joined
·
20 Posts
Discussion Starter · #20 ·
Well this is some fun info to look into. I figured the suggestions were heading this way. I don't know how to check the output shaft for proper design and will look into it. Thanks for all of your help, seems like this bitch will sit for much longer.
 
1 - 20 of 37 Posts
Top