Adding ABS Sensor to D44HD

[jaluhn83]

What's involved in converting the earlier D44HD w/o ABS to have the front ABS sensor used on the 92+ rigs? Is the sensor mount machined into the knuckle or is it a separate piece? Tone ring looks like it's part of the hub, so that should be simple, just swap hubs. Any differences in bearings, spindle, etc?

Right now I'm running my speedo and cruise control off the ring gear sensor on the 10.25 rear. I am planning to swap that out for a D70 rear which will then leave me without a speed signal and I have been trying to figure out the best approach to add another signal source. It occurred to me this afternoon that putting a front ABS sensor on one of the front wheels might be a good solution is it can be done without too much headache. I think it is likely that the output signal form will be similar so it should be compatible although the front tone ring looks like it has about 1/3 the teeth which might be an issue for the cruise.

Thanks,
~John

 

[riotwarrior]

Why swap to 70 is my ?

 

[jaluhn83]

Because I can.

Current axle is a 10.25 3.55 open. I have a good low mileage D70 LS 4.10 unit sitting around. I have concerns about the condition of the 10.25, and would be happier knowing I have a solid rear end. Also want the limited slip and smooth housing of the D70 for off road use. It will also probably get rear disc brakes, which eliminates the inboard drum downside on a 70 and the 4.10 will work well with a double od since I'm looking at getting a DNE2 od box as well.

 

[riotwarrior]

What about a tone ring in a d60 from van? See bout that??

Thinkin outloud for ya

 

[jaluhn83]

Ya know, I hadn't really though about that, and I even have a van D60....

Will it fit though? I'd expect since the ring gear is different sized the tone ring would be as well, and the bolt pattern on the carrier would also be different.

Doing that would also involve figuring out how to mount the sensor and taking the internals of the rear end apart to swap the ring. Nice thing about the front end is it seemed like a couple of cheap junkyard parts and not much effort would get it done.

 

[LCAM-01XA]

OK, your signature says you have an 85 truck. In 85 the cruise didn't look for a VSS from the axle, it used a VSS on the t-case output shaft. Also the speedometer was cable-driven... What does custom instrument cluster actually mean?

But really, why can't you use a VSS on the tail of the t-case? Seems to me that would be way easier than modifying axle knuckles and such... Hell if your t-case is in excellent shape just swap the output shaft - we just did that last week to make a 1-ton PTO-capable 1356 VSS-compatible, and as it turns out some of the non-VSS ones actually do have the right shaft and only need the indexing ball, the clip, the gear, and the tail housing with the machine hole (so like 10 min of work, if that). If you have a PSOM in place of the cable drive speedo/odo that will get super-pissed at the t-case VSS, but if it's an aftermarket gauge can't it be reprogrammed to read off a different signal?

Another thing, you mentioned swapping hubs for the 44 - correct me if I'm wrong here, but weren't all 92-up with 4-wheel ABS halftons? Meaning that's a 5-lug hub, not 8-lug like what you need? What's the plan for that, weld up the 5-lug hub flange and redrill it for the 8 on 6.5 pattern?

Finally, you are aware the late-model DRW vans come with a D70 axle, right? One that has a VSS on its diff. So unless Dana changed diff dimensions on you, you should at least in theory be able to pull the tone ring off one of those and drop it onto your carrier... Maybe. Then you drill holes for the VSS itself.

 

[junk]

I also was wondering about pulling the VSS off the transfercase. my 89 has a little sensor deal that goes in the speedo hole. Then it has a speedo cable hookup and a wire hookup. Wires for the cruise system and cable for the speedo. Not sure how it compares signal wise to the rearend. Like is it a similar ouput? IDK.

A guy Swamp Donkey back in the day before he started doing performance diesel stuff. He made a tone ring that fit on the output of his transfercase and a little bracket to hold the sensor. It seemed to work really well for him. He'd gone to rockwell axles in his 92-97 supercab and lost the VSS.

Lcam - That interesteing on the Non-vss transfecase. I have a non-pto transfecase sitting here that looks brand new. Guessing i'm going to add the VSS to it and use it in my Crewcab.

Jeremy

 

[LCAM-01XA]

The difference between the transmission-mounted VSS and the axle-mounted one is in the type of the wave (sine for trans, square for axle IIRC) and also the frequency.

On the 1356 t-case when you pull the tail housing look for a single blind hole about 5/16" in diameter and half that in depth, it will be about 2" away from the ball bearing IIRC. If you have that hole you don't need to swap shafts, just add a gear and indexing ball and its retaining clip (in that order), plus obviously a tail housing. If the shaft is smooth all the way from the ball bearing to where the splines for the yoke start, and there is no hole to be seen on it, then you need to swap tail shafts in addition to the other parts I just mentioned. No big deal, but it does require splitting the main case and dealing with the chain drive and the oil pump and the shift forks.

 

[jaluhn83]

I'm using a 92+ electronic cruise setup which uses the PSOM and the VSS for a speed signal, and I also have an electronic Isspro speedo that needs an input signal. The speedo is programmable and would probably work fine off the trans sensor, but I expect the PSOM is different. I suspect the cruise is only setup to work with a certain range on input frequencies, which means I need to keep the VSS frequencies roughly the same, ie I need ~100 pulses per tire revolution or ~25 per driveline rotation.

I am also planning to throw a Doug Nash od box behind the t-case, so i would need a sensor off that output, not the t-case, and I don't really want to mess around with cutting up that housing to fit a sensor if I can help it.

The thought with the front ABS sensor was that it would all be bolt on once I got the right parts.

Did they not have a 8-lug 4wd D44 truck with ABS? I was assuming that they started putting ABS on the trucks in the early 90's and the 4x4 would get it as well - is this wrong? I honestly don't know.

The D70 van ring might work if I was able to find one for a reasonable price... Might be able to adapt a 10.25 one as well, or simply machine one.

Haven't heard of Swamp Donkey in many years - used to have his page bookmarked but now i can't find it. I may do something similar putting a tone ring on the back of the output yoke somehow and sticking a sensor on that.

 

[LCAM-01XA]

Just looked up the OBS cruise wiring diagrams, and yes you are correct in that the PSOM converts the axle VSS signal for the cruise brain. Thing is tho, it's the same signal that gets fed into the ECM. The same EEC-IV ECM type that in prior years had exactly zero issues understanding the signal straight from the t-case VSS. Now looking at the older EVTMs, the cruise and the ECM also share a signal there - and it goes straight to the t-case VSS. Same single wire (per device) hookup as the OBS truck between the PSOM and cruise and ECM. Too many similarities there, if I were you I'd be extremely tempted to connect the OBS cruise to the t-case VSS and see what happens. Obviously have a spare cruise brain on stand-by in case the experiment fails.

Never seen or even heard of a 3/4-ton or larger OBS with 4WAL. Heck they didn't get air bags and crumble frames, it kinda makes sense if Ford skipped them with the fancy ABS as well.

 

[jaluhn83]

It's not the signal form that I'm concerned about it's the frequency. The owners manual gives ~25 mph as the lower limit for cruise, which I take to mean that the system is programmed to have a minimum VSS input freq to activate. I'd expect there's also an upper limit if not programmed than simply due to electronic design of the system. The axle tone ring is something like 108 teeth, so it's going to output ~60k pulse/mile. The t-case drive is probably setup for 1000 rev/milefor a mechanical speedo, and IIRC the sensor is something like 8 pulse/rev, which gives ~8k/mile. If I'm right with all this, then the different frequency would mean the cruise wouldn't activate until about 200 mph.... not very useful.

Seems I missed that ABS on these was rear only - somehow I had in my mind that they did the 2 front wheel and the rear axle... oops.

Looks like there a number of D70 axles that used a sensor, and a tone ring for one is ~$20 new, so that may be the best route. Not 100% sure it would fit, but worth trying. Have to pull the ring gear assembly out, but that shouldn't be too hard and I was probably going to have to do that anyway to set the housing up properly for machining disc brake mounting flanges. Drilling the hole for the sensor is going to be fun - have to figure out how to get it set squared up properly and in the right spot.

 

[LCAM-01XA]

Yeah, 1000 rev/mile mech speedo output sounds about right after running the numbers for our particular setup. Thing is tho, do we know for certain the PSOM doesn't change the VSS frequency before sending it to the cruise and the ECM? That would be key, if divides it by some massive factor for it to fall within EEC-IV specs you may be in the clear. This is assuming all EEC-IV ECMs are programmed with the same vehicle speed frequency parameters. According to the now defunct Old Fuel Injection (Ford Fuel Injection before FoMoCo pulled their typical a-hole move and lawered up against the poor guy) the EEC-IV assumes 8000 rev/mile, there is no mention of different models of EEC-IV ECMs being programmed for different frequencies. So if the axle VSS is cranking out 60k, the PSOM has to be cutting them down for the EEC to understand. And if the EEC understands them, so does the cruise, as they are fed the modified VSS signal in parallel.

 

[jaluhn83]

I don't know at the moment, but it seems unlikely to me. Changing the frequency of the signal seems like a more difficult solution then simply alerting the coding of the ECM - I'd expect it would be fairly easy to change the software in the ECM to divide that input signal by a factor of 10 or whatever.

On the other hand that would explain why the signal runs through the PSOM first.

Thankfully we can resolve this fairly easily - just need to jack a tire up on the truck and check the VSS and PSOM out frequencies. Don't have an o-scope to actually look at waveforms, but hopefully I can get a frequency.

 

[LCAM-01XA]

Yes, give it a shot on the frequency measurements - how do you plan on doing that without the o-scope tho?

 

[jaluhn83]

Well, looks like you were right. Testing at ~30 mp I had ~650 hz off the VSS and ~65 hz off the PSOM - looks like a simple 1:10 divider, and 65 hz @ 30 mph is consistent with ~8,000 pulses/mile.

I have a multimeter with a frequency setting. Not a fluke but good quality and something like $200 list - not the common chinese ones. Wasn't sure if it would work with a signal like that but it didn't seem to have any issues.

Next step is to find a t-case sensor and see if it will work off that. Will be nice if it does, saves me some effort.

Bad news is I also took a close look at the gears on the D70 and found a chipped tooth, so it woln't be a simple of a swap as I'd hoped. Had 2 of these, one low mileage and one from a beat up truck, wonder if I kept the wrong one?