After the big cummins swap into my friend's '96 Bronco, all factory gauges are working great with the 6BT except the speedo, because the new rear axle doesn't have the tone ring for the VSS.

Only option I can think of at this point is looking to run some kind of pulse generator off the NP205 speedo output. I'm trying to figure out what the speedometer expects for a signal...how many "pulses per MPH" to put it one way. The Autometer cable-to-electric sender puts out 16 pulses per cable revolution, is this comparable to the factory signal or can I get a calibration unit from somewhere to fix it?

Any other ideas for this?

you "may" be able to somehow swap the sensor from a 13-56, with the vss in the t-case into the 205. Or, I know a buddy of mine put the tone ring from the stock 8.8 around the front hub on the 44, and it worked like a charm, after a 44/9" swap.

from alldata online ( have it at work ) :flipoff2:
The Programmable Speedometer/Odometer Module includes the Speedometer, the Odometer, and the Trip Odometer, all of which are electronically controlled by a programmable integrated microprocessor. The microprocessor receives a speed signal input from the Differential Speed Sensor (DSS), and uses a programmed conversion constant to convert the signal to the standard 8000 pulses per mile speed signal output. The Programmable Speedometer/Odometer Module is serviceable only as a unit.

The speedometer is also used to provide Speed signal for correct operation of the vehicle's EEC module and speed control (if so equipped). Because of this, it is VERY IMPORTANT to change the speedometer's internal conversion constant if the size of tires on the vehicle is changed. Changing the conversion constant to the proper value when the tires are changed will also make sure that the speedometer retains the original factory-set accuracy.

the factory / dealer can reprogram speedos to some extent - superlift also makes a calibrater - don't know if this helps

So...8000 pulses per mile as a starting point. Counting the frequency from that value will give you the actual speed. Interesting.

The computer in the '96 bronco is effectively gone. No compuiter functions are needed to run the 12V Cummins motor or the 5-speed ZF trans so we pretty much just chopped it and threw it away.

I have a frequency counter, so I guess I can try swapping in some sort of electrical sender into the NP205, either from a BW case or some other source, and figure out what sort of pulse rate we can expect.

I think that number was the essential thing I was looking for, as everything else relates to that as far as the vehicle display goes. Thanks for the info.

Heres how a friend made his work on a 44/14B swap

http://www.explorerforum.com/forums/showpost.php?p=1505053&postcount=249

this is the very reason most of us go with a sterling. let us know what you come up with please, just in case i ever break the sterling.

this is the very reason most of us go with a sterling. let us know what you come up with please, just in case i ever break the sterling.

Isn't the tone ring on the 10.25" larger though (compared to the 8.8)? I'd think this would throw off the speedo reading unless you compensated for it by using appropriately larger tires.

it may be, but most are running larger tires, thus the need for the sterling.

With my 40's, everything is fine. The speedo is still about 10 percent off tho. In trying to rationalize it, why would the tooth count be off? the sterling comes on 250/350's both 2 and 4 wheel drive. the largest stock tire would be like a 265 or there abouts. I would WAG that they are the same.

here are some tone ring threads I have saved that I havent looked at for years

http://hometown.aol.com/jzettel73/Military_Axle_Swap_5.html

I thought I had more

search for LeDuc's racing shop. he has some aftermarket tone ring that allows you to swap a 9" IIRC.

Vans came with a D61 that also had the tone ring, and some people have swapped a tone ring into a D60, but i cant find that article. i think it was done by a member of 2bigbroncos.com

What axle do you have in there, a 14b?

Current axle is a 10.25 semi-float, which we used because it was the right gear ratio and had a limited-slip in good shape. That was swapped in back when it was still a 302 so a full-float is definitely something we want to put in now.

We might have a FF 10.25" laying around, haven't looked in a while, but if we do it's likely from an 80's truck or van and won't have the tone ring anyway. We've been looking for a D70u as there's rumors that certain mid-90's vans had them and also had the tone ring. Had a 9" in it before w/the 302 and blew up two gearsets so I'm not doing that again. 600+ ft-lbs of diesel torque wouldn't work out too well for that.

The larger issue is that the factory computer is pretty much gone. Nothing else on the truck needs it. I'm looking over the wiring diagrams in my spare time to find out where I can feed a pulse signal directly to the speedometer.

The reason I was thinkin the tooth count would be different is because the tone ring is the same size as the ring gear (8.8" vs. 10.25"), but I guess that doesn't mean the pitch is the same. It doesn't matter stock vs. stock because the speed computer is programmed from the factory to work with whatever configuration it came with.

This is the last stupid electronic thing on the whole build.

http://i106.photobucket.com/albums/m272/f250rollinon37s/62605120.gif

http://i106.photobucket.com/albums/m272/f250rollinon37s/62605121.gif

:smokin:

I have the opposite problem. Zf-6/np271 in a 92 dodge, which had a cable drive, and neither the tranny or the tcase has provisions for that. Anybody know if aftermarket speedo/odo would fit in the same hole as the stock unit? It's round @ least. Pry run tone ring off my dana 70u, where do I get that business?

I think 87 was the first year for vss in the sterling other than that maybe just run a gps in the truck :P more accurate anyway

Sent from my DROID2 using Tapatalk

Years ago we put a 14 bolt in my buddys 96 F150 4x4. To get the speedo to read and trans to shift we made a bracket and mounted it to the pinion support mounting bolts. The bracket supported the factory 8.8 rear axle sensor. Then we had a friend with access to a plasma cam cut us a few different tone rings from mild steel that had the ID cut to just lightly tap onto the 1350 yoke and then spot welded for temp. The main reason we did this was to keep the E4OD shifting right. We ran 5.13s with 40s and the speedo ran right (i think we might have put a superlift speedo recalibrator on the truck also) and trans shifted on time. I wish I had some pictures. That was pre digital camera or picture phone days.

I would say in your case, try to get a set up to run off the Tcase. Something to convert the mechanical speedo drive on the 205 over to the appropriate electrical pulse signal you need.

I have counted a bunch of ford tone rings. Almost always it is 108 teeth (but I have heard of a few others such as 112). So if you divide the teeth by the gear ratio (108/4.10 for example) you get roughly 26 pulses per revolution of the driveshaft.

Speedometer cables are roughly half of driveshaft speed (I can think of 8 tooth driving gear and 16 tooth driven) but they can also be asl little as a third of driveshaft speed (7 and 21 tooth gears), so the 16 pulse tone generator isn't going to cut it.

I started but never finished a project that involved taking a tone ring off a front axle (something in a junkyard on the ground) that had 44 teeth on it. I have counted some that were in the low 50 thooth count as other options. I bushing sleeve turned on a friends lather and put on the transfer case output yoke. Trouble is 44 pulses is more then the 26 mathmatical correct count. But if you remove every other tooth, 22 is close to 26. At least close enough to be in the range that you can probably dial in the speedometer. Different gear ratios, different tone ring tooth counts can very easily change the results.

Just something to think about.

I have counted a bunch of ford tone rings. Almost always it is 108 teeth (but I have heard of a few others such as 112). So if you divide the teeth by the gear ratio (108/4.10 for example) you get roughly 26 pulses per revolution of the driveshaft.

Speedometer cables are roughly half of driveshaft speed (I can think of 8 tooth driving gear and 16 tooth driven) but they can also be asl little as a third of driveshaft speed (7 and 21 tooth gears), so the 16 pulse tone generator isn't going to cut it.

I started but never finished a project that involved taking a tone ring off a front axle (something in a junkyard on the ground) that had 44 teeth on it. I have counted some that were in the low 50 thooth count as other options. I bushing sleeve turned on a friends lather and put on the transfer case output yoke. Trouble is 44 pulses is more then the 26 mathmatical correct count. But if you remove every other tooth, 22 is close to 26. At least close enough to be in the range that you can probably dial in the speedometer. Different gear ratios, different tone ring tooth counts can very easily change the results.

Just something to think about.



It is NOT always 108 teeth :shaking: The 1 ton stuff (10.25 and 10.50 I believe) have 120 teeth. If you search around, there's a pretty easy method for determining your conversion constant, and it's even easier to change the calibration once you know your constant. In this forum, I even have a post or two regarding the PSOM.

But, since our DAN decided to bump a fucking 5 year old thread to ask a not really related question, whatever