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VSS, I searched,** Has cruise, No green box, now what? ***

Mudbug1979

Mudbug1979

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I am putting TBI on my 84K5 with a 700r4 from factory. CAN I get a VSS from like an 88 K20 with a screw in speed sensor for the transfer case and use that for my signal for my TBI for lock up and what not? The one from Painless is 130.00, so I'm just wondering if I could wire the OEM into the Painless harness. THanks.
 
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Your truck could have a VSS already, it would be mounted to the back of the speedo and have three little wires that run to a little green box. If it's there then it's just a matter of connecting it to the TBI computer assuming it's a 7747 style computer. If your truck doesn't have a sensor you could install a speedometer cluster that has a speed sensor. The only other option would be an inline sensor from Painless or Jagsthatrun.com.
 
'84 will have VSS already if the truck had cruise.

If not, it SHOULD be setup for it, so you'd just need the buffer from an '83-89 C/K/R/V.

At worst the hole in the speedometer won't be tapped for the mounting screw, but speedometers are the same until 1989, so it's a simple, easy fix.
 
Vss

it does have the vss and little green box tied into the back of the speedo. I also have the speedo from the 87 suburban that this system came out of. Which wires do i tie into it. I am using the Painless 60101 harness. i will search in the mean time but I'd like to have a second opinion before I mess something up.
Thanks.
 
Black/white wire is ground, pink/black wire is switched power. They are probably connected properly already, just verify before doing anything else. The Brown wire is what you are concerned with, it goes to the speed sensor input wire in your Painless harness which should be brown as well. It's just that simple.
 
x2

Power/ground are already wired correctly, if you are concerned, trace the leftover wire to the cruise module, and that's your VSS ECM feed wire.
 
VSS box

I removed the dash cluster today and there was no VSS green box hooked to the back of the speedo. Only thing I can tell that is hooked to the tranny is a little vaccume solenoid/sensor, that runs off of the manifold. I have the complete cluster out of an 87 Suburban that was TBI with the VSS green box on it. Question now is, I only have the speedo and the wires to the green box. What do i connect my Painless Harness too off of that box or am i going ot have to have more than that to make this work? Any pics would be great help. Thanks again.
 
You might need to talk with Painless. I believe they still consider VSS an "add on" that you need to pay more for. They should be able to tell you where the signal wire needs to go. It's pin A10 on a '7747 GM ECM.

VSS is NOT connected to anything other than the speedometer for the pre-'90 stuff, so don't confuse yourself.
 
I am doing the same conversion, i did'nt think it would matter but I saw it mentioned above nothng goes to the tranny does it? I aam running a th400.
 
Harness

The Painless has the wire to hook up to the vss source but on my cluster, I only have the Little green box on the back of the speedo, nothing is connected to it. CAN, I just hook the painless VSS wire to the green box or am I going to have to buy the VSS inline sensor? Also if I removed the little vaccume solenoid that was on the fire wall that the transmission wires ran to will my transmission shift right now?
 
You will want the transmission vacuum switch, unless the Painless kit runs the TCC. That's a requirement with the 700 to keep heat down, but it's simple to run either way, with the switch, or through the ECM as the TBI trucks were setup.

VSS buffer has another connector obviously, the one you are missing. Just cut out a three wire connector (wrecking yard is fine, essentially any GM car from 1981-about 1986) and wire it up. 12V, ground, and VSS out signal. Look for the connector, it should be there unless the cruise module was removed, or someone cut it out, which would show with the cut wires...which would make splicing in a replacement that much easier, since it will already be powered/fused correctly.
 
harness

The Painless harness does have the Four prong plug that plugs into the driverside of the tranny. SO, if I get one of those plugs the VSS out will be what I hook to the VSS IN signal wire on the painless harness and POW , should work like a champ correct?
 
My first thought would be that it SHOULD, but that depends on painless and the ECM you are running.

Really need to talk to "Painless" (lol) to make certain, voltage on the wrong wire to an ECM could be a bad thing.

GM used at least 3 methods of obtaining a VSS signal, if not 4 or 5 in the TBI year-ranges, so it would be unwise to assume that Painless is setup for the correct one.
 
SO, if I get one of those plugs the VSS out will be what I hook to the VSS IN signal wire on the painless harness and POW , should work like a champ correct?
Click to expand...

There are a lot of assumptions here; assuming the PROM is for a 700r4, the VSS is wired correctly, the transmission is wired correctly internally and all of the pressure, temp switches and the lock-up solenoid is working then yes it will work like a champ.

Fortunately there is only one way to send a speed sensor signal to a 7747 (and I'm ASSuming it is) computer and that is connect the brown wire on the speed sensor pigtail to the brown wire (A10) on the computer. The new body style trucks used a buffer between the speed sensor which is a 40x signal and the computer that is using a 2x signal but they still used A10 as the input.

Post up what the service number is on your computer and the code off of the PROM and we can tell if it will work.
 
Computer

I have the 7747 or what ever sequence it is. It came out of an 87 2wd Suburban with a 700r4. I have the complete harness out of the sub which I removed the plug that goes to the green box today and traced the wires down to the ALDL port, fuse box, and to another connector. I will look tommmorow on the K5 to see whats there hiding in the harness. Does this make any sense?
 
The pink wire probably went to the fuse box, the black wire went to the ALDL among other places as it's a ground, the brown wire should go to a 6 or 8 way connector which plugs into a mating connector that goes to the computer.

Wire the VSS up the way I posted earlier and it should work.
 
there are 2 pigtails that plug into the green box correct? I have the one with the pink, black, and brown wires. but I cant seem to find the other. what color is the wire, and where would it go? im sorry i made a dumb mistake and need help.
 
If you've got three wires, you may be done. All you need for injection VSS is power, ground, and the signal wire to the ECM. Brown SHOULD be the signal wire, GM was consistent with that.

The buffers could be setup for cruise and the ECM, so may have used more than one plug for output.
 
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