JJ IROC

Anyone know what drive the VSS in an auto transmission on an 1988 Firebird. Is it a magnet on the tailshaft?

Kevin91Z

There is a plastic gear on the tailshaft, which spins another plastic gear on the magnetic pulse generator, which sends the signal electronically to the computer. I believe its 2000 pulses per minute. Firebirds used the electronic speedo starting in 1989, while the Camaro didnt switch until 1990.
If you change your rear end gears, you need to change the plastic speedo gears in the tailshaft. The VSS stays the same.

JJ IROC

Thanks. Out of curiosity it's 1989 not 1988 when Pontiac switched to electronically driven speedo or vss? I thought my 88 had a vss not a cable but I could be wrong.

respectirocz

i think you mean pulses per mile

if i rememebr correctly, pontiac switched to a vss/electronic speedo in 1987
camaros kept the mechanical speedometer until 1989
but i could be wrong

JJ IROC

Yeah I think you have it would the 1987 Firebirds switching to VSS and I know Camaro's didn't switch till 1990.

Anyway next quick question then. I have a Transmission out of a 1987 Camaro that was already rebuilt and modded before the it was taken out of the Camaro. Can I use this transmission in place of the Transmission in the Trans Am with just swaping the VSS deviece or what else would I need? Thanks.

Kevin91Z

Whooops! I meant pulses per mile, yes.
I am pretty sure the Firebirds switched to electronic speedo in 1986 as I have a friend with an 86 Trans Am, and his is electronic, while another 85 Trans Am I know is cable.
Camaros definitely switched in 1990.
Yes, the Firebird tranny and Camaro tranny is identical, except for the VSS speedo signal. Use the speedo gears and VSS from the Firebird and you'll be fine.

89Vert

86+ T/A's and 90+ camaros have electric driven speedo

its very easy to convert a cable driven speedo tranny to a electronic speedo drive tranny,
take all of 10 seconds
at least in a T5