i have swapped from an 89 305 TBI to an 89 350 TPI with the same 700R4 trans...my car originally had a mechanical speedo and the new harness came with a hookup for the electronic VSS on the trans.... i know the ecm needs a signal of the cars speed....do i need to install a VSS on the trans or is the mechanical speedo sending a signal to the ecm?....is there any way i can still have my speedometer reading and have a VSS in the trans? Thanks guys,
Steve

 

just use the carrier that you were using before holding the drive gear

 

Your 89 350 TPI is out of a Firebird?

 

Yea its from a firebird.

 

Ehrr...I believe you will need a buffer box. One can be had off an 86+ T/A for a small amount of dough. It's a yellow box attached to the ECM that relays the VSS sensor in the trans to both the speedo and ECM. IIRC the ECM wants a 2000ppm and the speedo wants a 4000ppm (on newer model maros/tas) Been a few years since I played with it though

 

The VSS on your mechanical speedo is on the back of the tach. With some creative wiring you could probably make it work.

 

i actually have on eof those buffer boxes because i got the harness with the engine...how do i hook it up? will i still have a speedometer considering the one in my camaro was mechanical?

 

lol, buffer box, thats funny. Whats so hard about making the connection for your speedometer mechanical like its supposed to be. the VSS sensor is behind the speedometer faceplate. gees.

that would be the "correct" way. nuff said.

 

The hard part is that my new harness is wired for a VSS in the trans. I have the mechanical one hooked up but i need to get the signal to the ECM. Because my harness is wired for a VSS in the trans, i dont think the VSS behind the speedometer is being used. Is it? I guess i shoulda asked that in the beginning.

 

The Firebird you got it from had an electronic speedo. Both the ECM and the speedo used the signal from the VSS on the transmission. Your Camaro has a mechanical speedometer, and its original ECM took its signal from the VSS on the back of the cluster. You may be able to modify your wiring to let the Firebird's ECM use the signal from your original VSS.

 

Any idea how to wire it? Also I saw something in jegs that looked like it was a vss with a mechanical hookup and electronic. Ever heard of it? Thanks again.