vss/speedometer/cruise. wiring idea to make it happen. need opinions.

Here is my ideas to keep the speedo and cruise working. I have a 95 Tahoe 4wd and want it to function. seeings how nobody one the face of this planet can tell me exactly what to do to mate the ls harness to run them, ive put together some theories.

Option 1. Leave the factory harness and pcm in the truck. To my knowledge the only thing engine side I need is TPS signal for the transmission to function. splice the ls and TPI engines tps sensors together and trans should work.

Option 2. use an ls harness to control the trans and splice the tahoes factory VSS sensor into the ls VSS wiring and the tahoes ECM should read that and the speedo and cruise should work.

Im not sure what part of the factory ecm sends signal to the dash but I have read of all kinds of screwed up signal issues and speedometers not working.
But here is my understanding on how this work. PLEASE correct me if im wrong.

VSS sends signal to tahoes ECM, it then converts that into whatever it needs and outputs it to the speedometer and the cruise control module. SO instead of bypassing the factory ecm why cant I just send the proper signal to the ecm so it can do its thing.
Either by sending it VSS signal or by sending it TPS signal and letting it control the 4l60?

I hope I am making sense out of this.

Every thing should work by simply splicing in to the existing wires and will work with out the old ecm.
Your tuner should also be able to correct the pcm to make your tach function properly.
You can search this form or Google for "obs ls swap wiring" and it pull up tons of info for tapping into the trucks original wiring. Don't pay attention to the 96+ wiring threads as there different for us 95- guys. I do know for a fact the wires for the cel, tach, and speedo are behind the glove box (iirc the vss wire goes there as well.
There is absolutely no need for the old ecm, might even have problems getting your cel to function right if the cel wire was left connected to the older ecm.

As for cruise, it should function properly if your harness is spliced in correctly so long as you have drive by wire throttle body. Drive by wire is a different ball game and is explained in several threads hear and on other forums.

This is the same information im getting everywhere. Everyone just keeps saying you can just splice in here or there but NOBODY can tell me where. I just keep hearing about this mythical wiring unicorn. and googling every term possible hasn't yielded any results. NONE. I am the one tuning it and I at this point I am not worried about the tach. I am only wanting to make the speedo and cruise function. which seems impossible. I just wish someone would tell me what wires to send where. if not I guess I will proceed with my theories and see what happens. I just wanted to see if anyone else has tried this.

dude, you need to calm down. your getting the answers that you need. just because they are not what your wanting to hear (i.e. using both pcms) or the fact that you just plain dont understand doesnt mean they are wrong! i told you already to just add the wires to the harness you have and your good to go. this has been answered a million times. just pay attention to what your reading!!

i shouldnt be spoon feeding your ass but i dont want to see any more new threads by you about this! so take it and figure it out.

in the obs trucks, the vss does NOT go straight to the speedo/cruise. it goes to a VSSB/DRAC box depending on year. as yours is a 95, it has the VSSSB. it deciphers the vss signal and THEN sends it to speedo/cruise. on the newer trucks, the vss goes straight to the pcm, an IT deciphers it and sends it to speedo. so your only options are to use the vssb box like i did or use the pcm and make sure its programed for your tire/gear ratio and your done for speedo!! wow. super difficult...

as for cruise, it depends if your runniing DBW or DBC. if DBW, its F***ing easy! remove old cruise module and replace with TAC, splice in 4 wires and done!! thats how i did it and it works flawlessly. if you run, DBC, afaik, you keep the old cruise box hooked up to the vssb, run your cable to the TB and it will controll it physically. simple as that.

here are two links that i have posted numerous times on this site that you can read and figure it out. if you dont know how to read a wiring diagram, thats not our problem.

this explains the drac/vssb http://www.tbichips.com/drac/ i explained a nice "how to" to get the speedo correct in my build thread which is in my sig... maybe you should take a look....

here are wiring diagrams for damn near any car you need including the cruise circuit for your year truck. http://search.ebscohost.com/login.as...ile=autorefctr

user:student
pass:uatc

stop whining and do more searching. the answers are out there. you just havnt looked hard enough. i found all this info and hooked it up in working order without asking a single question about it. as stated, there is NO NEED for both pcms. im running both but the old is SOLEY for the ABS which what i hear is not even necessary as the new pcm can controll it also.. SSSOOOO, FORGET the old pcm!!! all you need is the LS pcm and your golden!

http://www.ls1truck.com/forums/lsx-t...dometer-2.html
http://www.ls1truck.com/forums/lsx-t...-wiring-4.html post 38 has wiring diagram for drac box which on my 1992 is behind the glove box. ls pcm speed output goes to the lt blue black wire for speedometer . The trans speed output goes to the ls pcm. Look at first post for the pins it goes to if you have the 1999-2002 pcm
http://www.ls1truck.com/forums/lsx-t...-wiring-4.html
Here is the ls wiring diagrams http://lt1swap.com/wiringharness.htm

You will have to have the ls pcm programmed to get your speed correctly in the ls pcm and for the speedometer reading in your truck.

I thank both yall for the help. I think one of the reasons I am getting so frustrated is because I HAVE been searching. for about a week straight and haven't found anything definitive. I have searched this forum non stop too. Maybe I was using the wrong terms. This is the last of the project and I am beyond ready for it to be over. I am going to try to sort this out after work. if I cant figure it out then, I will just have to deal with it.