i have a ls1 t56 swap i just finished in my 91 camaro and all my guages work except the speedometer. the car was a 305 tbi 5 speed. motor and trans is out of a 04 gto. i had hawksthirdgen do my wiring harness and i thought it was going to work but i doesnt. any sugestions? i don't know if i need to get rid of the vss buffer box or even if its still wired in at all. my other thought was the converter box... it doesn't move at all right now...need to fix asap...thanx ahead of time...

 

You have to wire the speed output wire from the pcm to the buffer box connector.

 

do u know what color the output speed wire is or what pin it is?...and what wire do i connect it to at the buffer box???

 

What pcm do you have ?


Lovely if they charge what I think they do, and then dont even let you know what you need to do to get it fully operational.

 

Brown wire, Pin C on the vss buffer connector is where the vss output from the pcm.

 

i have a f body pcm

 

PCM VSS output is at the red connector, pin 50.

 

just so im right...im conecting the output wire from the pcm to the brown wire from the buffer box so that the buffer box isnt doing anything anymore. its just running staight to the back of the cluster correct...sry if im wrong im just trying to figure all this out in my head right now without looking at the car...thanx for ur help

 

Yes

 

Sometimes the speedos dont like the feed out of the PCM. Splice in a parallel feed direct from the VSS out at the trans to the speedo as well as the PCM

 

WTF ?

The vss output is nowhere near the correct rate for the speedometer.

Dont know where you got this idea, but the correct way to make it work is exactly what I said.

PCM output to brown wire at terminal C of the buffer box.

 

Hes got an adjustable box no? Done it a few times now on numerous transmission swaps. Works great for me the only times ive had any issues was trying to use the PCM to feed. Been swapping all sorts of transmissions long before LS1's....

Whats the reluctor ring count from the factory t5 vs the t56?

 

No he doesnt have an adjustable box, he said he thought he might need one which he doesnt.

The box is something to use when you are using a T56 with a thirdgen engine/harness/computer.

The reluctor count is 17 teeth on the T56, pulse/mile will come down to final drive.

T5 is 4000/mi

 

With a 3.73 gear the T56 vss puts out about 7566 pulse/mi

3.42 6937 pulse/mi

4.10 8316/mi

 

ok i did it the way z28ricer said which makes sense now and it works...i was driving down the road with my friends gps on his phone and it was 5mph off. the trans is out of a 04 gto which is geared different from a f bodys. i still have the factory 3.08 gears in it. im getting a strange rear in the winter months so im assuming its off bc my stock gearing is different from what the trans was made for correct?thanx for the help....

 

Can I make the speedo work without the PCM?

 

Yes you can use the dakota Digital SGI-5, the vss wires connect to it, and then use the 4000 pulse/mi output to the speedometer.