HO speedometer pulses per mile or rev?

[Vanimal]

I'm swapping my tcase and i need to change the speedometer setup since this transfer case doesnt have provisions. I have a plan, but i need to machine a tone ring to put on the output shaft and fit in some sort of speed sensor, like a hall effect switch or whatever. does anyone know of a sensor i can use that would work with the stock 91 HO ecu and wiring (2 wire)? i also need to figure out how many lugs to put on the tone ring.

 

[jeeperjohn]

You could use an aftermarket speed sensor setup but you would have to make it a stand alone system. If you can find an old speed sensor from an early model and take it apart you could count how many pulses are generated per rotation of the output shaft. That would give you the number of pulses needed to match the stock setup. I might have an old speed sensor you can use, I will have to look.

 

[Vanimal]

i need some sort of hal or prox sensor. something that will pick up the tone ring. i figured out the pulses already, so i just need to find a working sensor. i have a few prox sensors kicking around, but none that will run off of the jeep's amperage. they run on as low as 3v, but i assume there isnt enough current to turn them on.

 

[87manche]

your basic ford EDIS sensor is cheap, readily available at a parts store for replacement and is a 2 wire VR sensor.

You can find them for anything that used EDIS in the junkyard. Ford Escorts with the 1.9, crown vics, rangers basically anything Ford and in the 90's.

 

[Vanimal]

i dont think a vr sensor will work, i have a few here and no dice so far.
the stock sensor switches at approx 230hz at 100mph. it does not fluxuate voltage as far as i can tell. just on-off-on-off-on-off.
what i was thinking was to run one of my prox switches off 12v into an optoisolator to switch the vss wires on and off. other than that, i'm out of ideas.

 

[souske]

you could do like urkel, and install a chalkboard to write down how fast you think you are going...

 

[Vanimal]

looks like i may need to get a dakota digital sgi-5 or something similar to convert the signal. anyone have a better idea?

 

[Rush Power Systems]

you could do like urkel, and install a chalkboard to write down how fast you think you are going...

WHO? And why do you have a picture of our king and queen on a road trip? sorry could not resist

 

[5-90]

Per revolution. That's why drive gears need to be changed with tyre or gearing changes. Even if the speed sensor is at the wheel (as it is on bicycles,) you'd have to change the setup if you change tyre size.

Aren't there GPS speedos that can be integrated into the IP? Ground track speed is one of the four only data I want from a GPS setup (Lat/Long/Alt/Spd. Don't bother with a map, I can read it myself.)

Seems to me that if you lose the GPS signal, you probably have bigger problems to worry about...

I recall Popular Mechanics running a series of articles on a "DIY Digital Dashboard" quite some time ago - you might want to pillage around in your library to see how they did it...

 

[Vanimal]

not sure if we're on the same page. i'm trying to integrate a different speedo sensor into the stock system. i need to do this because my transfer case is different and doesnt allow for a gear driven speedo sensor. i want to keep it as simple and close to stock as possible. definitely no GPS or aftermarket speedometers.

 

[CobraMarty]

I thought I read somewhere that there are 5 pulses per revolution. I can't say for sure but 5 sticks in my mind.

 

[5-90]

not sure if we're on the same page. i'm trying to integrate a different speedo sensor into the stock system. i need to do this because my transfer case is different and doesnt allow for a gear driven speedo sensor. i want to keep it as simple and close to stock as possible. definitely no GPS or aftermarket speedometers.

Which is why I mentioned the Popular Mechanics article - their solution was rather simple, and should be adaptable. If nothing else, it gives you a nuts-and-bolts on how to figure your revolutions and translate that into land miles.

There are other solutions out there, but aftermarket "solutions" are just that - they're presented as black boxen. If you see how it's built, you can work out a way to adapt it (kinda like how a good teacher will never tell you an answer - they'll just help you figure it out...)

 

[jeeperjohn]

So the problem is not getting a signal, it is getting a signal that will play nice with the stock computer, right?

 

[Vanimal]

So the problem is not getting a signal, it is getting a signal that will play nice with the stock computer, right?

correct. i already figured out the pulses per rev and pulses per mile. i just need a sensor that jives with the stock computor, or a way to convert it to do so.
5-90, i know enough about electronics to know this isnt something worth making myself.

 

[Rush Power Systems]

Interesting, the 91 systems is rather simplistic, I am thinking of a magnet(s) on the drive shaft and a mag switch(s) mounted on the T-case or a bracket, are we on the same page?

 

[Vanimal]

i want it inside the transfer case. if you saw my driveshaft, you'd know why
the dakota digital sgi-5 is what i need, according to them.

 

[Rush Power Systems]

i was going to go that route, but i did not think you had any way of providing input for the sgi-5

 

[5-90]

correct. i already figured out the pulses per rev and pulses per mile. i just need a sensor that jives with the stock computor, or a way to convert it to do so.
5-90, i know enough about electronics to know this isnt something worth making myself.

Depends - I recall the article making it easier than I first thought, and PM always did a good job of explaining how things worked.

I think the stock computer used a Hall effect sensor, with the rotor in the transmission/transfer case being either 2 pulses/rev or 4 pulses/rev (the pulse generator did have to be balanced, so it would likely be an even number. 2 or 4 is easiest.)

It is easier to take the reading from inside the case, instead of from the driveshaft - unless you've done a slip yoke eliminator, and have a slip joint mid-shaft (and set up your pulse generator upstream of the slip joint in the shaft - else you'll articulate and slide right out from under the pickup.)

Also, didn't a number of later-model vehicles use a similar drive/pinion arrangement, only using a magnetic pulse generator instead of a mechanical drive cable? I don't know if you can swap parts around to get that into play, but it may be worth looking into...