1987 Trans am gta with 5.3Ls/4L60E with a non working stock speedo

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Apr 4, 2018 | 10:08 PM

Boomboom87

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1987 Trans am gta with 5.3Ls/4L60E with a non working stock speedo

Hey guys. Need a little help here. I have a 1987 trans am gta with a 5.3 LS, and a 4L60E that I had bought last August. Been getting things fixed up here and there. Well I’ve came to the stock speedometer that doesn’t work. It wasn’t working when I bought the car. Well anyways, the girlfriend had bought me a Dakota digital box for Xmas. And after about a month of searching this site and ls1 tech I think I am just more confused then I have answers. Can anyone chime in and put me in the right direction? It has a “pocket harness” on the engine side from what I was told by original owner. I found where the old buffer box would reside, but no buffer box.Everything else seems to be plugged in correctly even the C207/C221( I think that’s what they are) I guess I’ve read so much, that I’m not sure what to do. Thanks. Hope to hear from someone! I know this is a redundant question from all the posts I’ve read. Haven’t seen anyone with this particular situation.

Last edited by Boomboom87; Apr 5, 2018 at 12:30 AM. Reason: To better describe issue

Apr 5, 2018 | 07:05 AM

scooter

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From: NJ

Car: 92 Firebird

Engine: 4.8 LR4

Transmission: T56

Axle/Gears: 3.45 9 Bolt

Re: 1987 Trans am gta with 5.3Ls/4L60E with a non working stock speedo

You can drive the stock speedometer with the LS computer, not sure why you have the DD box, or even which one. You're going to have to start probing wires and see if you have continuity from the dash to the output of the ECM.

I would read through the swap guides for the LSx, that will give you the info you need and what wires you should be looking at

Apr 5, 2018 | 11:25 AM

Boomboom87

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Re: 1987 Trans am gta with 5.3Ls/4L60E with a non working stock speedo

Well the DD box isn’t installed yet, its the SGI-5 E universal signal interface unit. I was told by a buddy that the LS computer wouldn’t send the right signal to the speedo to read. But after all my searching I’ve read that the computer should be able to. Ok. I will check the swap sites and see what they have to say again. Maybe I missed something. Thank you.

Apr 5, 2018 | 11:42 AM

scooter

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iTrader: (11)

Joined: Sep 1999

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From: NJ

Car: 92 Firebird

Engine: 4.8 LR4

Transmission: T56

Axle/Gears: 3.45 9 Bolt

Re: 1987 Trans am gta with 5.3Ls/4L60E with a non working stock speedo

I am using the stock LS, red and blue, to drive the speedo in my 92 Firebird. You just need to set the gear ratio and tire size in the parameters. SGI5 would be if you're getting the wrong signal and cannot correct it.

You want RED 50 for 4k pulse output as shown here
http://lt1swap.com/99-02_vortec_pcm.htm

Apr 5, 2018 | 12:11 PM

Boomboom87

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Re: 1987 Trans am gta with 5.3Ls/4L60E with a non working stock speedo

That’s what I have also is the red and blue. I came across something similar pertaining the the pins. I have to go out and check to see if the colored wires match from what I have to what you provided. So your saying I have to get into the computer and change those parameters for it to work? Shouldn’t i be getting something on the speedo regardless? Is there a way to do that other than with hptuners? Or am I overthinking this?