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Old 06-21-2020, 11:15 PM   #291
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It is a bit cheaper -- but it does say explicitly not to use for ABS -- I'm assuming that's a cover you a** by Dakota as I don't see why it wouldn't work.

Surprisingly -- I can find nothing about how the ECU/ABS system converts the AC signal into wheel speed. It seems "shimming" the sensor can lower/raise the AC voltage -- but I'm awfully confused because it seems it may just go off of "pulses" and ignore the voltage (within reason).

I'll call Abbott and Dakota tomorrow and ask them... I hope it is based on pulses and not voltage -- as then I could likely use a GM-style passive ABS sensor, which will be a lot easier to install directly into the tail housing of my NP271 since it is threaded versus the mount on the econoline ABS part.

Worst case scenario - I'll buy another Abbott/Dakota -- but honestly -- it'd be nice to just do this part mechanically!

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Old 06-21-2020, 11:24 PM   #292
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My Dakota is connected directly to EDIT (the wire from the differential to the ABS module under my hood). I am sure it is a CYA from them. Superlift used to sell tire calibration modules like these and stopped. Probably for the same reason. My Dakota works great. My ABS functions as normal. I don't know of an easier way to correct the Speedo than this. I agree that a mechanical setup is less complicated, but it is only as good as the sensor. If you could keep the sensor in the axle and use the tone ring inside with the Dakota modifying the signal, I think that would be more reliable than an externally mounted ring with tricky sensor spacing. What do you think about just using one of the rear wheel sensors for your signal?
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Old 06-22-2020, 11:02 AM   #293
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Hey Texas Tom -- what year is your van and what year is your rear axle? Are you sure you are modifying the signal "out" of the ABS module and not "into" the ABS module? Not trying to be rude -- just curious how that works since it seems the role of the ABS module is to turn pulses/ac voltage into DC voltage that the ECU can use to measure wheel speed -- but I cannot find detailed information about this on my service manual.


I'd love to use the existing tone ring/sensor -- but Ford moved to active-style ABS sensors for the later year axles (probably when they added 4 wheel abs). Mikerson did some research to try and figure out if there is a passive sensor that can fit into the existing hole -- but hasn't had any luck of yet (I think).

That certainly would be the best way to do it, I think:
https://www.sportsmobileforum.com/fo...tml#post262303

The "easiest" solution is to simply add the 120 tooth tone ring to the carrier on the axle and install the sensor back there (mounting it might be difficult) -- although given how the e-locker works -- some F-series guys say that when you turn on the e-locker it fudges up the ABS/speed sensor (the rear sensor on the F-Series controls the speedo even with the 4R100) -- which isn't ideal either.

Appreciate your feedback -- I'll report back what I hear from Abbott/Dakota. I imagine they have a very deep understanding of these systems.

We're all in this together!!
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Old 06-22-2020, 11:30 AM   #294
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Well -- the folks at Dakota told me the ABS modules look for "pulses" not voltage. The way to think about it is the AC voltage generated by a passive sensor the "strength" of the signal and the number of pulses is the "information" from the signal. Thus -- the closer the gap between the tone ring and the sensor the better - as that'll increase the strength of the signal and you can get the information right by ensuring the correct "tooth" conversion -- either electronically through the Abbott/Dakota unit or mechanically through the number of teeth.

I think I'm going to proceed with a 28 tooth tone ring inside the tailhousing of my NP271 like this guy:
https://www.nc4x4.com/forum/threads/....191665/page-2

Unfortunately I do not think I can modify that 40 tooth tone ring to 28 evenly spaced teeth -- but I imagine making a custom one will not be very expensive (probably cheaper than an electronic converter).
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Old 06-22-2020, 11:44 AM   #295
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Looks like you got your answer. I have the Dakota installed on my 2002 F350 7.3L. It is installed on the wire between the axle sensor and the ABS module under the hood. I chose to pick up the wire at the ABS module because it provided easy routing to my dash and it was easy to weatherproof my connections. It is definitely modifying the pulse signal, not voltage. Hope this helps someone out.
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Old 06-22-2020, 04:42 PM   #296
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Good deal. What year axle did you use?

EDIT: Sorry I see this was for a F350 -- so I assume you just changed tire sizes or gears?
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Old 06-22-2020, 04:58 PM   #297
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Correct. This was just for 35" tires on my 2002 F350.
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Old 06-22-2020, 11:24 PM   #298
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Yanno -- while we're on the topic -- are we supposed to ground out a pin on our PCM when we go into 4LO too?

I know I had to do that on my Astro to get the shift points correct for 4LO... but I haven't seen anything about that anywhere on any E350 4X4 builds.

I can't find anything suggesting the computer on the truck changes the shift points when in 4LO -- but you think it would... I know on some vehicles it turns off the ABS, etc. too.
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Old 07-21-2020, 01:13 PM   #299
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Any updates on this since you last posted?
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Old 07-21-2020, 01:43 PM   #300
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Nada -- I looked at the F-series wiring diagrams and it doesn't look like there is any 4LO signal to the ECM/TCCM anyways -- at least when I looked quickly.

It's probably because the shift points are determined based on the output shaft speed of the transmission -- which doesn't really care if it is in 4LO or not.

I think the shift points on the Chevy/GMC are determined by sensors in the diff -- so they are affected by being in 4LO.

if it were necessary, I'd imagine it would be obvious. In the Astro, if you do not the right pin of the PCM in 4LO, it won't come out of 1st gear (or maybe 2nd) because the sensors are out of range when you account for the gear reduction of the transfer case and it puts the tranny in "limp" mode or something.

I'd assume this issue would be found out already given the numerous number of vans already swapped. Also, since U-Joint is basically a full-time shop dedicated to E350 swaps, I'd be surprised if they wouldn't have uncovered this if it was an issue.
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