Are our VSS's mostly/all 8000 ppm?

tab a · Jan 5, 2017

As my previous thread indicated I put a 2000 (Explorer) 5R55E in a 97 Ranger, that had had a 5R55E. But, since the VSS moved from the tranny to the rear axle---speedometer doesn't work.

Ordered a Dakota Digital SGI5 and cannot get it to work. I've talked to 3 different guys in their tech dept. without much progress.

They want to know if the two different VSS's are both 8000 ppm.

Anyone know?

Thanks.

RonD · Jan 5, 2017

Yes, the original 1997 VSS on the transmission tail shaft was 8,000 pulses per mile.

So you are now using the ABS rear axle VSS on the 1997 axle for speed signal?

They are the same type of VSS signal, AC voltage is self generated, the PPM doesn't really matter that much since it changes with tires size, it does matter as far as signal type but the point of the interface is to correct the pulse count per mile to show correct speed at speedometer and at computer for shifting

If you are getting no speed at all then I would suspect VSS itself, all the interface does is to allow you to adjust the VSS signal to correct speed.
If you can, lift rear wheels so they can spin and use volt meter set for AC Volts on VSS wires.
Should see about 1 volt with wheels spinning, the faster they spin the higher the volts
There is no voltage to speed graph, you are just testing if VSS is working.

tab a · Jan 5, 2017

<So you are now using the ABS rear axle VSS on the 1997 axle for speed signal?>

Yes.

One (!) of my points of confusion is trying to figure out if both sources would be putting out 8000 ppm (is that at 60 mph?) at the same speed. That is, at a speed that the rear diff sensor would be putting out 8000 ppm, would a sensor on the transmission tail shaft ALSO be putting out 8000 ppm, or would it be different, since the tailshaft and rear axle spin at different speeds?

I have a flashing red light, which DD tells me means the unit is happy with the signal.

I've tried many permutations of output, and calibration of the DD. Speedo didn't budge on any of them until nearly last try yesterday. Even then, at maybe 10-20 mph it might read about right for a second then would go back to zero for most of the time.

I'll check for AC signal when I can get back to garage. Wonder if I need to hook up other wire? Am using Pink/red for signal, but have not hooked up Green/B as I presumed it was ground, and would use connections at GEM, etc.

Thanks!

RonD · Jan 5, 2017

If the interface says it is getting a signal then VSS should be OK.

The rear ABS would output more than 8,000ppm usually

A 30" tire will rotate 700 times per mile
So the tone ring on the axle will also rotate 700 times per mile

The ABS VSS reads the tone rings "teeth" as they pass by, if tone ring has 20 teeth then that would be 14,000ppm, if it had 30 teeth then 21,000ppm

"The SGI-5E can recalibrate a 2,000 pulse per mile (ppm) through 250,000ppm electronic speedometer pulse rates, either up or down."

So I don't see an issue in the interface handling any ppm count, but you would be lowering it to get down to 8,000ppm

Hook up both wires until it is working correctly, then you can eliminate the "ground", if possible.
Yes, you most likely do not need the "ground", but if you have ever done any trailer wiring you know to NEVER ASSUME a good ground, lol.

TonkaMan · Jan 8, 2017

RonD said:
Yes, the original 1997 VSS on the transmission tail shaft was 8,000 pulses per mile.

So you are now using the ABS rear axle VSS on the 1997 axle for speed signal?

They are the same type of VSS signal, AC voltage is self generated, the PPM doesn't really matter that much since it changes with tires size, it does matter as far as signal type but the point of the interface is to correct the pulse count per mile to show correct speed at speedometer and at computer for shifting

If you are getting no speed at all then I would suspect VSS itself, all the interface does is to allow you to adjust the VSS signal to correct speed.
If you can, lift rear wheels so they can spin and use volt meter set for AC Volts on VSS wires.
Should see about 1 volt with wheels spinning, the faster they spin the higher the volts
There is no voltage to speed graph, you are just testing if VSS is working.

Are you sure the PPM varies? According to the Ford dealer service manual I have, everything assumes 8000 PPM. In the 97 model year the VSS sensor had various gears on the end of it that interfaced with the transmission. Every axle gear ratio and tire combination had a different gear with a different number of teeth to keep the 8000 PPM constant and accurate to tire speed. I found this out the hard way when I upped the tire size on my '97 2WD and got a speeding ticket. My speedometer was off by almost 10% compared to actual speed. I had to buy a $2 plastic gear that snapped on the end of the VSS sensor, that was color coded to the tire size. Different color than the factory one. Fixed it immediately.

In the 97's, everything is an end user of the raw VSS sensor data. The speedometer, PCM, ABS module, etc. all take in the raw sensor data and do their own thing with it. Starting in 1998 when the VSS was moved to the rear axle they added a module into the ABS that calculated the speed, and everything else then got the speed data from that rather than directly from the sensor.

RonD · Jan 8, 2017

Yes, 1995 to 1997 used VSS on tailshaft for speedo and computer(PCM) and yes it was 8,000ppm, cruise doesn't care, nor does ABS

1998 used VSS on rear axle which outputs much higher PPM count, so do the newer OSS on tailshafts, close to 32,000ppm
So the rear axle signal needed to be changed to 8,000ppm so speedo and PCM could use it, GEM was used or 4WABS unit was used to change high ppm to 8,000ppm, from 1998 to around 2001 I think, then PCM was used to feed corrected OSS signal to speedo.

OP's issue is that the newer 2000 5R55E transmission he swapped into his 1997 Ranger doesn't have a VSS, or OSS, on the tailshaft, so he doesn't have a stock module to convert the rear axle VSS to 8,000ppm, so he is using the SGI-5E module to do that

tab a · Jan 8, 2017

With the rear tires off the ground, and the vehicle in D, tach at 12-1500, I read about 7v ac on the Dakota Digital--i.e. input from the rear axle ABS.

The DD has 5 optional outputs, but only 2 of those are ac, the other 3 being 'square wave' outputs. I've tried most/all the combinations on the 2 ac outputs I can think of. Most show nothing. Some will make the speedo 'bounce' once, when first put in Drive.

Also have hooked up the G/B (non-signal) wire on ABS sensor directly to ground, without effect. I'm not sure this is necessary, as it was spliced into, and not cut, it should still work as original, I'd think.

The DD signal output is spliced into the original VSS wiring at the transmission. It occurs to me that the ground of that wiring pair is NOT connected to anything. Grounding that is the only thing I can think of left to try.

Will talk to DD again tomorrow.

Thanks.

RonD · Jan 9, 2017

How are you wiring to Speedo and computer?

The signal wires from the rear axle VSS should have just run to the ABS on a '97
So splicing in to the two wires and running them to the DD would be what you should do, so ABS is still connected and not effected by DD changes.

Then connect the two wires from the old VSS position(tail shaft) to the DD, these went to speedo, computer and Cruise, no connection to ABS.

Rear axle VSS=========DD======(original VSS wires)====Speedo/PCM/Cruise

tab a · Jan 9, 2017

That's how I have it wired, other than no ground from DD to original VSS, as mentioned. In (my

) theory, ground should be supplied by DD power ground, GEM ground, etc.. May be totally wrong.

RonD · Jan 9, 2017

It is a Pulse signal so not technically a Ground, but that wire is Grounded.

In 1997 the GEM gets the PPM but only used it for 4WD Low shifting, 0 ppm required
So I didn't included it because it won't effect anything if GEM has or doesn't have PPM

tab a · Jan 10, 2017

This is REALLY getting to be a PITA. :annoyed:

And Dakota Digital seems almost as confused as I am.

They suggested I check ac output, which I did--7.53v. Maybe slightly more than they expected but ok. Input ac at that time was 3.5v

I then tried removing the DD from the equation and directly connecting the diff ABS sensor output to the old tranny VSS output wire, looking for ANY speedo reading. No speedo response and the engine began rhythmically faltering.

Double checked that I had the right signal output wire from the tranny VSS, by checking resistance to ground, of both VSS wires. Surprised that signal out wire was only 15k ohms, compared to similar measurement at ABS sensor of 15M ohms.? Both of the other 'ground' wires measured .6 ohms.

Other thoughts?

Thanks.

gw33gp · Jan 10, 2017

I also use a Dakota Digital SGI-5 C unit to correct my speedometer after I installed 4.56 gears that I swap back and forth with 33" tires and 31" tires.

I tied into the wire that goes to the speedometer because Dakota Digital recommended not tying in before the ABS system and I could not figure out which wire to use after the ABS system. I have 4 wires connected to the DD unit. One is the input signal, another the output signal, 12V to power the unit and ground. It has been working fine like that. My DD unit has several different connectors for the output and one of those (output 3) is for the 8000 ppm signal. It also has a Sensor ground (if needed). I don't know what determines if it is needed. The 4 switches must be set to get the calibration close. They have a recommended setting then let you go from their. I would guess you have already done those things though.

If you don't get anything without the DD unit, there must be something wrong with the signal from the VSS.

The way mine is hooked up it corrects the speedometer but the computer still gets the signal directly from the VSS. When I have the 31" tires on it, the compute thinks I am going over 90 mph when I am only going 80. This kicks in the speed limiter at 80 and the engine starts missing. I doubt this has anything to do with your engine faltering but it is a bit of information to consider.

tab a · Jan 10, 2017

<If you don't get anything without the DD unit, there must be something wrong with the signal from the VSS.>

Could be, though FWIW I had no ABS light or CEL with it and the old trans.

There is an output 3 that is 8000 ppm but AFAIK that is only with the High to Low application. Is that what yours is set on? Didn't think our 'input' from diff was that high, i.e. greater than 32,000.

Sounds like you just cut the speedo wire and used one end for input and the other for output, to/from the DD? Where, physically did you cut it?

Thanks for the info!

gw33gp · Jan 10, 2017

You mentioned that you have a flashing red light and DD tells you that means the signal is OK. My information tells me that a flashing red light with the green light on indicates you are in the fine calibration mode. If the green light is on and the red light is off, that indicates power is on and no signal is present. If the green light is flashing and the red light is off, power is on and a signal is present. Maybe you have a slightly different version of the SGI-5.

I remember I did not have a speedometer reading when I first connected everything. I tried a different output and got it to work. I think I worked with output 1 and 2 but output 1 worked for me. That is with switches 1,2 & 4 in the off position and 3 in the on position. My instructions seems to be conflicting. One area indicates output 3 is 4000 ppm AC and another indicates output 3 is 8000 ppm. They have different switch positions so that may be why they change.

tab a · Jan 11, 2017

The DD unit I have has no switches, per se. There is a button that you push to set the device to change PPM from High to High, H to L, L to H, and L to L.

No green light that I'm aware of.

I think I'll next try disconnecting the RABS box. Will directly connect the RABS sensor to the VSS wiring and see if speedo does anything. Maybe that will rule out the RABS causing problems. Is the box behind the radio, on the right?

Other thoughts?

Thanks.

Are our VSS's mostly/all 8000 ppm?

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