I have an 86 IROC-Z with a mechanically driven speedo, I put in a 700-R4 out of an 88 camaro, and the wiring harness is an 88 also, it has an elec. connection for the VSS or road speed sensor, whatever u want to call it. Okay, I have the speedo cable screwed directly into the tranny, and nowhere to hookup the VSS, I have a VSS, but it has no provission for a speedo cable, I went to the local auto parts store and looked through the books and cant find one with both. My friend said they made one that had a small cable about 3-4" that came out of the tranny and the sensor went in between that and the main speedo cable. If anybody can crawl under their car and look to see how its setup that would be great. A part number off of the parts would help too, if one can be found.

 

The speed sensor for your '86 iroc is on the back of the speedometer head. It is the optical type. All you need to do is screw in the cable to the trans. The other connector is used for torque converter lockup. The '88 iroc has the exact same setup as yours. I know this because I have an '88. The firebirds and trans am cars are the only ones that year that would have a vss at the trans. Hope this helps.

 

That yellow thing on the back of the guage cluster is a speed buffer, does it send the speed signal to the ecm? My torque converter is plugged in it uses the same plug as the fourth gear plug{ the four prong white plug }, so I just hang the two prong plug up out of the way and dont worry about it?

 

Yes, that is what gm used in the camaros and yes it sends the ecm the appropriate signal.

Now just to clerify, what harness was changed in the car and did it come out of the 88 camaro as the tranny?

 

I converted a throttle body to tpi , wasn't hard to do, but yes it is the same harness from the car the tranny came out of. It was a parts car that I bought and stripped, I tore it apart so long ago that I can't remember how it was setup, I thought I needed that sensor down there but if I don't I won't worry about it. Thanks for your help.

 

Let's start at the beginning. What engine did the car have originally?

 

The car was originally a 305 tpi iroc-z w/700r4, 1986, it had no drivetrain in it when I got. I found a 1992 305 with speed density from a guy I worked with at the time. I built a new 355 and put that tpi system on top of it, of course modified. Well I came across a wrecked 88 sport coupe with a tbi 305 and 700 r4 in it. The tranny was beefed up and put behind the 355, the wiring harness was converted to run the tpi, eight inj. plugs lengthed out the iac and tps wires, switch wiper motors and relay board on the drivers side, and so on. The car will run and all of the accessories work fine, you'd be surprised how similar the harnesses are. Well eventually I got to hooking up everything on the tranny and the four pin plug is plugged in, but theres the two pin plug still hanging, I have a tranny driven vss sensor and it will plug in to it. but its not the right one for the car, because it wont accept a speedo cable on the other side, I thought there was one supposed to be there and I have no idea what it looks like or a part# for it. I can't remember if the 88 sport coupe had one or not. This is where my confusion begins and brings me here now!

 

Thats a big help. You are basically running the 90-92 SD TPI setup then.
The 90-92 cars had an electronic speedo in them, thats why you have the extra 2 wire connector at the tranny. You obviously changed wiring harnesses under the hood and the dash and the ecm from the 88 otherwise it would not run. The maf and sd ecm's have different pin outs. If everything is working on the car, no other problems, then this pic is the litle critter you need. Painlessperformance has them and you can buy it through jegs or summit. part number is 60116. It will set you back a 100 bucks though.

 

Yes that little bugger would probably work perfect. I forgot to mention I am running haltech e6gm ecu , and it uses the two plug 88 harness, not the 90-92 three plug harness, underneath the dash is all stock 86 wiring, me and my friend who happens to be a master electriction went through all the wiring schematics for all the cars to make sure every thing was hooked up right, all that needed changed was some pinouts in the ecm connecters for the haltech ecm, it uses speed density, put is wired like a mass air flow system. But as for the sensor it looks dead on thanks for the info. Know I need to figure out where I'm getting signal from, I'm just gonna have to trace wiring to see which one the haltech wants to use. Thanks for your help, I greatly apprieciate it.