Ok I swapped from my T-5 to an LT-1 T-56 everything is in the car working flawlessly wish exception of the speedometer..

I've searched all the threads and couldn't find a definitive answer for my question so here goes..

How do I get my speedomoeter to work properly? I wired in the vss from the trans but it appears to send a different signal than the factory unit seeing as how my speedo pegs as soon as I start rolling..

I imagine I need some sort of conversion box like that dakota digital one or something correct? or is there a VSS I can get that will fit the transmission and run my speedo like normal?

Any help is appreciated...

Thanks
AL

 

Yes the Dakota box should work in your case.... right now I'm guessing your speedo pegs the instant the car starts moving.... that would be because the T-56 VSS puts out about 17 pulses per rev or some such, but your car is expecting 4. So it thinks you're going at warp speed. The Dakota box acts as a divider.

Here's what you've got.



You need to electronically divide the # of pulses down quite a bit to get to 4 per rev, as you can see.

 

I wonder how well it'd work to just cut all but 4 of the teeth off the reluctor.....

I know the spacing would be slightly uneven, but AFAIK the $8D code doesn't check the speed or timing of the pulses, it just counts them as they come I'd think $6E (what your '89 runs) would work the same way. Trimming 13 teeth off with a die grinder might be the cheapest and easiest way to make this work. If my IROC still had a factory cluster I'd try it and see for myself.

And yes, the 4th gen T56 reluctor has 17 teeth. So 17 pulses per driveshaft rev.

 

You'll notice there's no aftermarket 4 tooth reluctor ring. That is because it's not 4 pulses per revolution in anything.

Early Third-gen VSS was driven by speedo gears or within the speedo and is 2 pulse per speedo cable revolution (2002 square-wave pulses / mile.)

Then, the 90-92 cars all had VSS driven by speedo gearrs at the trans. and were 4 pulses per "speedo cable revolution" (4004 sine-wave pulses / mile.)

Some early 1993 F-body T56s had an 11 tooth reluctor. Later ones were 17 tooth. 1994-up Automatics got a 40 tooth reluctor.

Those are 11 / 17 / 40 pulse per driveshaft / output revolution. Number of tire rotations per mile * gear ratio * 11 (or 17 or 40) = the pulse per mile for comparison purposes.

 

Thats what I thought thanks guys

 

Yar. 4 pulses per driven gear revolution, not per driveshaft revolution. My mistake. It's been a LONG time since I worked with the factory speedo setup.