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VSSB Troubles/Questions

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Extremesounds13

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So I am finishing some odds and ends on my truck that I did the cummins swap in and I am working on the speedometer. I removed the PCM when I did the swap cause it was not needed and everything I have done so far has worked but I hadn't done the speedo yet. Anyway I finally got the harness hooked up and plugged into the speed sensor on the back of the transfer case and when I drove the truck I have no speedo. My question is there were three wires two brown and one brown with white stripe that ran from the VSSB to the PCM would those three wires cause my speedo or VSSB not to work? Off the wiring diagrams I have from what I can tell those wires just tell the computer whats going on so I don't understand why it wouldn't work without those. Any help is appreciated Thanks.
 
the brown wire is supposed to be battery voltage with IGN on, and black/wht is the ground. So those need those two things. The brn/wht wire is the only one that really goes to the PCM with the speed signal.
 
The job or reason for the VSSB is to change the analog/pulse signal from the speed sensors to a digital signal that the ECM can read. Don’t know if this will help you though with the engine swap. IIRC when you do an engine swap such as you have, you need to install the stand alone trans ECM from like a 93 or older. Maybe one of the more qualified people here can let us know for sure.
 
I got two different wiring diagrams of the VSSB so I could trace down each wire, one from checker one from my GM dealer, and neither one matches my harness, they both have about five wires correct and five wrong. Anyone know where I can get another good diagram? Also if I take the VSS out of the t case is there a way to test it to see if its good, thats the only part that would be different from when it was all working with the 6.5, and besides the wires that went to the PCM.
 
Schwind said:
The job or reason for the VSSB is to change the analog/pulse signal from the speed sensors to a digital signal that the ECM can read. Don’t know if this will help you though with the engine swap. IIRC when you do an engine swap such as you have, you need to install the stand alone trans ECM from like a 93 or older. Maybe one of the more qualified people here can let us know for sure.
Click to expand...

Ya I kinda know the basic idea of how it works, when I did the engine swap I used a dodge trans and then a gm transfer case, so all my wiring plugged right back in for the VSS. I took the VSS out of my t case and was going to put it in the one in the truck but it was different, the plug was the same but the mount and magnet on the end was different, do you think that matters? I was under the assumption all those GM speed sensors were the same in the older trucks?
 
OK,

need to know a bit more info before we can proceed:

Trans case year and type in originally in the truck.

Trans case year and type you put in the truck.

Year of the truck.

All the speed sensors in the 88-98 body style read a 40 ppr signal off the transfer case VSS. This goes to the DRAC (or VSSB if you prefer). the DRAC sends out the conditioned signal to the ECM, Speedo, Cruise, etc as each as looking for a different signal. IE: 2000, 4000 etc..

Also, have you done as Buddy pointed out?
 
I told you which wires you need to apply power and ground to. Do you have a brown wire and a black/white one on the connector that you left disconnected?
 
buddy said:
I told you which wires you need to apply power and ground to. Do you have a brown wire and a black/white one on the connector that you left disconnected?
Click to expand...

Oh ya sorry buddy I forgot, I do have power to the brown wire and ground to the black/white. You are talking about the connector right at the VSSB right? The brown and black/white were right next to each other then about four pins over was another brown, it did not have power but i am assuming that it is for something else.
 
great white said:
OK,

need to know a bit more info before we can proceed:

Trans case year and type in originally in the truck.

Trans case year and type you put in the truck.

Year of the truck.

All the speed sensors in the 88-98 body style read a 40 ppr signal off the transfer case VSS. This goes to the DRAC (or VSSB if you prefer). the DRAC sends out the conditioned signal to the ECM, Speedo, Cruise, etc as each as looking for a different signal. IE: 2000, 4000 etc..

Also, have you done as Buddy pointed out?
Click to expand...

The truck is a 1994 GMC 3500

In the truck original was the original 1994 241 transfer case, but it did have a PTO drive on it, never used, but it was there, I was going to use this transfer case but because it had a PTO drive the input shaft was not able to come out so that I could put the dodge input shaft in.

The transfer case that is in the truck now is out of a 1993 suburban and it is a 241 also, but didn't have the PTO drive so I was able to take the input shaft out and install the dodge input shaft. The transfer case was identical to my old one and even the vss plug and transfer case switch plugged right in.

And I have done as buddy suggested, I just forgot to post the results so I did above.
 
With that diagram, then make sure C15 is still going to speedo. C9 has ignition voltage, C7 and C12 are still connected to VSS, C8 is connected to ground. As long as its all there the speedo should work. C10 goes to antilock break controller.

In my 94 there is the undocumented red/white wire to C4. The smaller connector on the VSSB
 
buddy said:
With that diagram, then make sure C15 is still going to speedo. C9 has ignition voltage, C7 and C12 are still connected to VSS, C8 is connected to ground. As long as its all there the speedo should work. C10 goes to antilock break controller.

In my 94 there is the undocumented red/white wire to C4. The smaller connector on the VSSB
Click to expand...

So I checked everything and I have all that, but tell me more about this red/white wire, I have another all data diagram for my truck like the other one I posted but it had the red/white wire on it, but since I didn't have the red/white on the harness at my VSSB I got the other diagram instead. BUT on my original t case there is a small one wire plug(brown wire) that comes out of the t case real close to the speed sensor, and the new t case does not have that. Could that be a problem? What would the wire do, and why don't I have the red/white at my vssb, and any idea what the red/white does?
 
three at the t case switch for four wheel drive(that all works) then at the end by the drive line there is a plug on the case for 2 the violet/white and green/white that are twisted together. But on the old t case at the rear next to the vss plug there is just a wire coming out that is brown and the plug is about six inches down the wire, does that make since?
 
So finally today I decided to tackle the speedo issue AGAIN. I started earlier today and tested and verified all wiring at the VSSB and the cluster and the speed senor on the T case. All the wiring tested good for continuity and I had power and ground at the VSSB but still nothing worked. So I ran to the local parts store and bought a new speed sensor to go in the T case, I installed it and went for a drive and nothing still. At that point I checked all the wires again to be safe and then called my brother who has a 94 dually with the 6.5 so its almost identical to my truck and I borrowed his VSSB and put it in my truck and went for a drive and still NO SPEEDO!! So at this point I don't know what to do any help would be appreciated.
 
The red/white is for cruise control, so you wouldnt have it if not equipped with cruise. You might ask TheFerminator, since he did a DMax swap, he must of tackled the speedo, see if he had any issues.

Does the odometer work?

Are you sure there are gear teeth pressed onto the output shaft where the VSS is located in this transfer case? Or did dodge have the gear teeth in a different place on the output shaft?
 
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Have you hooked you volt meter to the VSS wires and took it for a drive. It should get up to 10-20v on the AC setting, depending on how fast you drive. I'm also wondering if there is a speedo gear mesh problem in the transfer.
 
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