My 87 GTA has a 350 trans that someone swapped in. I keep getting a code 24 and have no speedometer. What I read about this code is that the ecm is not getting any signal from the vss which affects the IAC and ignition timing. I usually have to hold the gas pedal to the floor and it runs really rich "rollin coal" is what my son called it the other day. What can I do to get the vss signal to the ecm ? I don't want to spend any money on it since I am going to do an LS1/4L60E swap soon.

 

Depends on what tailhousng and parts are on it.

If it has a 700-R4 tailhousing and 700-R4 speedometer gears, use the 87 VSS and connect to the wiring like stock. Might have an incorrect one.

If it has different speedometer gears, get an aftermarket VSS that threads onto the speedo gear sleeve.

 

It looks like a 700r4 tailshaft and vss. I don't know about the gear inside.

 

what do you mean when you say you "have no speedometer"?

that there physically isn't one in the car, or that it doesn't register speed?

does an 87 GTA have a mechanically driven speedo like a Camaro? if so, then the VSS is built into the speedo head and you probably need a cable..

 

The speedometer needle doesn't move. The tailshaft has a speed sensor with 2 wires. No cable whereas my sons 86 iroc has a speedmeter cable.

 

Any ideas ?

 

Pop the VSS out and verify there are gears in there.
It'll be speedometer gears, but they drive the VSS. All third gens had this.
If it has them, you pretty much need to follow factory service manual technique to troubleshoot the wiring & VSS to determine location of fault.

 

Yep, there's gears in there. But they don't mesh. The gear on the output shaft is too far forward.

 

I don't know the TH350 output shaft speedo gear locations off the top of my head.

If the rear is on jackstands, put it in neutral.

With the VSS popped out, spin things and look to see if there is another hole rearward on the output shaft. If there is, remove the torque arm from the bracket, pull the driveshaft, then the tailhousing. Depress the gear clip, slide things back and put the gear where it needs to be.

If there's no additional hole, but there's a correct place for the gear to sit, use a diamond sphere dremel bit set. Start w/ the tiny round one and add a hole for the clip where it's supposed to be to retain the gear.

And just think of how much faster this would have gone if you had checked those speedo gears and posted about them in post 1!