86 vss questions

[mx34n4]

Somebody please help... I am installing a tbi from an 88 model into an 81 model that was a diesel. I have everything done except the vss signal. I am installing an 86 model gas gauge cluster and its has the vss, my question is this...Does anybody know how to wire this vss into the ecm? it has a 4 wire plug and i have the pigtails. One wire is yellow, one is brown, one is black, and one is pink or red with a black stripe. Conventional wisdom would say that the pink and black are power wires and the brown is a signal wire to the vss input and the yellow is a signal to the cruise module. I tried it like this and get nothing. Also, does the optical sensor emit light to recieve back off of the rotating blades? Is the sensor 12v powered? Maybe I have already cooked mine. Thanks for any help.

[68 TT]

I would start with a wiring diagram for a TBI optical VSS Suburban (87-89) and see what it calls out.

I started this for my conversion but haven't finished all the research yet.

I am probably going to pull an under dash harness out of a TBI Suburban to simplify things a little too as I am also converting to an OD auto trans from a manual and to the column mounted wiper controls from the dash mounted stuff on my 78.

[D O C]

what size hole did you drill for the vss sensor in the 205?

[68 TT]

Originally Posted by D O C

what size hole did you drill for the vss sensor in the 205?

The one he is using is mounted to the speedometer and has on optical sensor that reads the VSS info off of the speedo head. The speedometer is cable driven so no mods to the transfer case are needed.

[centexan]

Originally Posted by 68 TT

The one he is using is mounted to the speedometer and has on optical sensor that reads the VSS info off of the speedo head. The speedometer is cable driven so no mods to the transfer case are needed.

I am in the process of cleaning up someone elses mess in my truck (74 with a TBI install). I am wanting to put in a 205 transfer case. So to make sure the VSS works correctly, I just need to make sure that the cluster is one that has the VSS connected to the speedo head and not the transfer case? And why are you using one from a TBI suburban? Is it more likely to have the VSS at the speedo head vs the transfer case. Thanks for the help!

[68 TT]

Originally Posted by centexan

I am in the process of cleaning up someone elses mess in my truck (74 with a TBI install). I am wanting to put in a 205 transfer case. So to make sure the VSS works correctly, I just need to make sure that the cluster is one that has the VSS connected to the speedo head and not the transfer case? And why are you using one from a TBI suburban? Is it more likely to have the VSS at the speedo head vs the transfer case. Thanks for the help!

The Suburbans are just more common and more years were available is all. The truck stopped in 87 when the Suburban kept using the same system through 89.

Seems like there are many more Suburbans in the wrecking yards than trucks too. I think people keep and fix up the trucks more often and give up on the Suburbans & junk them.

[1976K5CHALET]

That vss was more of an optical eye for the cruise control...
Also being cable driven it is going to fluctuate.
I'd order a stand alone 2 pulse 2 wire from Howell and do it right
by putting the horse before the cart.

[68 TT]

Originally Posted by 1976K5CHALET

That vss was more of an optical eye for the cruise control...

It does both. It has the output for the cruise control and one for the ECM with the proper pulse rates for both. The same thing was used in the 87-89 square bodies with TBI from the factory before they went to the electronic speedometer in 90 & 91.

Simple and easy to retrofit into a square body for next to nothing.

I'd much rather have a GM part on my truck than a one-off aftermarket item only available from one source like Howell or JTR. Common GM parts make it very easy to get replacement parts if anything ever fails on you in the middle of a road trip or vacation.

[mx34n4]

Originally Posted by 68 TT

It does both. It has the output for the cruise control and one for the ECM with the proper pulse rates for both. The same thing was used in the 87-89 square bodies with TBI from the factory before they went to the electronic speedometer in 90 & 91.

Simple and easy to retrofit into a square body for next to nothing.

I'd much rather have a GM part on my truck than a one-off aftermarket item only available from one source like Howell or JTR. Common GM parts make it very easy to get replacement parts if anything ever fails on you in the middle of a road trip or vacation.

Thanks 68TT.. I think this is the easiest way to attack the vss problem on a square body, after all it worked for GM. Since I am changing out the Diesel gauge cluster anyway why not give it a shot...its free.