I did search this and but didn't find exactly what I was wanting to know.

I have a 89 T/A that had a 305TBI. I am taking it out and putting a carbed 406 in it.

The tach should work right? All I need is to put the tach signal wire on the HEI distributer. I am pretty sure this is right.

My big question is about the speedo. I saw in a post that the VSS uses a yellow buffer box under the dash. Will this work separate from the ECM? Do I need to rewire the yellow box so it has power? I took the entire ECM harness out. I unplugged the bulk head from behind the front passenger fender and pulled out the ECM. I don't remember pulling the yellow buffer box out, but it's been a few weeks.

Thanks for any help.

Jason

 

ttt

 

Use a manual speedo, problem solved.

 

I'm not using a mechanical speedo.


Anyone else?

 

I think the buffer box is connected to the ECM - but not dependant on it. I think that in some cases the VSS sends the speed reading to the ECM for TCC lock-up and it also sends the speed signal to the Cruise control system..... But I do not think the Speedo will be problematic after pulling the ECM out.

The only way to be positive is to find a wiring chart for the exact car/ engine/ tranny your working with.

The VSS box is usually mounted behind the passenger side dash trim panel ( panel under the dash pocket ) but sometimes they get pushed behind the dash housing.

 

i swapped to carb on a 91 rs, speedo works just fine. don't have to re-wire anything