What to do with VSS during axle swap

[stmitch]

So I've got an axle upgrade sitting here that would work pretty well in my truck, but the factory rear (2000 7.5inch) has the VSS located on the dif, and the new axle has no provision for this.

Looking for some general ideas on how to get around this. I'm sure others here have been in similar situations before. Let me hear your ideas!

 

[ratdude747]

So I've got an axle upgrade sitting here that would work pretty well in my truck, but the factory rear (2000 7.5inch) has the VSS located on the dif, and the new axle has no provision for this.

Looking for some general ideas on how to get around this. I'm sure others here have been in similar situations before. Let me hear your ideas!

May I ask what the new axle is off of?

I may be wrong but sometime in that period, after using the rear ABS sensor as the VSS (what you're describing) for 2 or 3 years they went back to using a dedicated VSS on the tranny.

As for what to do, I'd look for axle housing/tubes that had the provision if 2000 was before they swapped back to VSS. If not, all you're loosing is ABS, the impact of which depends on which kind you have (Rear only or four wheel).

 

[85_Ranger4x4]

What is the potential axle out of?

Later axles went to sensors on the axle ends (for roll stability control) like around 2010. Or course earlier axles have nothing.

 

[RonD]

Actually the axle VSS is for ABS and from 1998 to 2000 was also used for speedo, either thru 4WABS module or GEM.

No real way around it, 1995 - 1997 used VSS from old speedo gear setup on trans(2WD), or on transfer case(4WD), and you changed Speedo gear to adjust for changes

If swapping in a Ford axle you may be able to add the tone wheel, it just fits on behind the ring gear and then drill the cover plate and make a fitting to install VSS so it can read the tone wheel.
Tone wheel from 7.5" only fits 7.5" if going to 8.8" then you would need a tone wheel from an 8.8"

I have seen pictures of people adding a tone wheel to drive shaft, transmission end, and then mounting VSS there, but signal pulses wouldn't be the same because drive shaft rotation is 3 or 4 times more than rear axle, i.e. 3.45:1 or 4.10:1 rear axle ratio
The 4WABS module can be programmed as can the GEM so that could get pulses back for correct speed

Or you could get a count of "teeth" on the axle tone wheel you have now and then make or find a tone wheel that would match the same pulses per full rotation of rear axle but mounted on the driveshaft.
i.e. if current tone wheel had 40 teeth and rear axle ratio is 4.10 then 40/4.10= 9.75, so a 10 tooth tone wheel would do 41 pulses for each full rotation of rear axle, 10 x 4.10= 41, close enough for government work,

Found a picture of that type of setup: http://s414.photobucket.com/user/gury410/media/My Truck/IMG_1502.jpg.html

 

[85_Ranger4x4]

If swapping in a Ford axle you may be able to add the tone wheel, it just fits on behind the ring gear and then drill the cover plate and make a fitting to install VSS so it can read the tone wheel.
Tone wheel from 7.5" only fits 7.5" if going to 8.8" then you would need a tone wheel from an 8.8"

I think the carriers are different too, otherwise you would be shifting the ring gear approx 1/4" closer to the pinion... which won't work.

 

[RonD]

Sorry, it doesn't go on/behind the ring gear itself, it just slides on to the back side of what the ring gear is bolted to, can't remember what that is called, lol.
Just looked it up, I think that part the ring gear bolts to is just called the differential, so tone wheel slides onto the differential.

Picture here: http://www.supermotors.org/getfile/195598/fullsize/106_0642.JPG
It is just a press fit not bolted, it has no weight and nothing touches it so it just spins with differential

 

[stmitch]

Thanks for the advice guys! The axle in question is an 8.8 from an 04 Cobra. I found a deal on CL that was too close to me to pass up, so it's been taking up space in my garage for awhile now while I deal with other projects, and troubleshoot potential issues. I had the bed off this weekend, and realized that the VSS might pose a problem.

I figured with all of the axle swaps that off road guys do, somebody would have a simple solution for eliminating or moving the VSS.
The pic RonD posted with the tone ring on the driveshaft might be doable. I'd probably have to have a custom driveshaft made anyway.
Might be able to drill/tap the Cobra pumpkin or rear cover and locate the sensor there too. That will take a bit more thought and troubleshooting to figure out.

If anybody else has ideas/suggestions, I'm all ears.

I suppose there's always the option of eliminating the VSS from the tune and switching speedometers to a GPS based unit too right? Something like this: https://www.google.com/#q=gps+speedometer&tbm=shop&spd=2220268047681371210

 

[stmitch]

Or, there are ABS tone rings on each axle where they exit the differential housing. With some math, and proper calibration tuning, could one of those possibly be used? That would allow the sensor to read the exact wheel rpm, (assuming the sensor can be calibrated for the number of teeth on the ABS tone ring).

 

[85_Ranger4x4]

Thanks for the advice guys! The axle in question is an 8.8 from an 04 Cobra. I found a deal on CL that was too close to me to pass up, so it's been taking up space in my garage for awhile now while I deal with other projects, and troubleshoot potential issues. I had the bed off this weekend, and realized that the VSS might pose a problem.

I figured with all of the axle swaps that off road guys do, somebody would have a simple solution for eliminating or moving the VSS.
The pic RonD posted with the tone ring on the driveshaft might be doable. I'd probably have to have a custom driveshaft made anyway.
Might be able to drill/tap the Cobra pumpkin or rear cover and locate the sensor there too. That will take a bit more thought and troubleshooting to figure out.

If anybody else has ideas/suggestions, I'm all ears.

I suppose there's always the option of eliminating the VSS from the tune and switching speedometers to a GPS based unit too right? Something like this: https://www.google.com/#q=gps+speedometer&tbm=shop&spd=2220268047681371210

First thought was just get a Ranger 8.8, it is the same thing and it bolts/plugs in. Then it hit me, '04 Cobra = IRS!

If the differential case is aluminum you may not want to go drilling holes in it... or maybe they they were nice enough to put a boss there for you too.

It is new enough to probably be set up for a tone ring inside, not like a 9" or something like that.

 

[don4331]

stmitch:

8.8" vss tone ring has 130 teeth (if I remember correctly). And mine had 3.73 gears.

So, when I installed the t-bird IRS rather than messing with the side ABS tone rings, I put a ring with 35 teeth on the pinion flange. (130/3.73 = 34.88). My speedometer is off by ~.3% as a result; less than difference between the 235/60R15s stock and 245/45R17s current.

The sensor was mounted on a bracket close enough to pick up the signal.

Example: http://www.explorerforum.com/photopost/data/3500/ebrake_tonering_02.jpg

 

[stmitch]

Looks to me like the tone ring in the dif case isn't easily done. Instead, they put a much smaller diameter tone ring on each axle between the dif case and the inboard CV joint.

If it's possible to adjust the VSS calibration with a tune, then I may be able to get by with just fabbing a bracket so that the VSS reads the ABS tone ring outside of the dif case. Ford has the ABS sensors setup that way from the factory. It makes more sense to me to use what's already there if I can, to reduce the likelihood that I screw it up.

 

[stmitch]

stmitch:

8.8" vss tone ring has 130 teeth (if I remember correctly). And mine had 3.73 gears.

So, when I installed the t-bird IRS rather than messing with the side ABS tone rings, I put a ring with 35 teeth on the pinion flange. (130/3.73 = 34.88). My speedometer is off by ~.3% as a result; less than difference between the 235/60R15s stock and 245/45R17s current.

The sensor was mounted on a bracket close enough to pick up the signal.

Example: http://www.explorerforum.com/photopost/data/3500/ebrake_tonering_02.jpg

So if I understand, you had an 8.8 stock, and counted the teeth on your stock tone ring, and based your calculations on that? Did you have the new tone ring custom fabricated, or was it an "off the shelf" part?

I'd love to see some more pics of your setup if you have any! It doesn't get the attention it deserves.

 

[RonD]

stmitch:

8.8" vss tone ring has 130 teeth (if I remember correctly). And mine had 3.73 gears.

So, when I installed the t-bird IRS rather than messing with the side ABS tone rings, I put a ring with 35 teeth on the pinion flange. (130/3.73 = 34.88). My speedometer is off by ~.3% as a result; less than difference between the 235/60R15s stock and 245/45R17s current.

The sensor was mounted on a bracket close enough to pick up the signal.

Example: http://www.explorerforum.com/photopost/data/3500/ebrake_tonering_02.jpg

Very nice set up don4331


The ABS sensors on the Cobra rear axle should work fine , it is a Variable Reluctance sensor just like the VSS.
Obviously the tooth count will be different.
Dakota Digital makes an interface to adjust pulses per mile to match input signal to speedo.
Here: http://www.dakotadigital.com/index....t_id=126/category_id=287/mode=prod/prd126.htm

You may be able to do that by reprogramming 4WABS module or GEM, but for $85 the SGI-5E Universal Signal Interface unit can be programmed by you fairly easily, vs getting a computer program or someone else involved and then involve again if there is a problem or other changes.

 

[stmitch]

The ABS sensors on the Cobra rear axle should work fine , it is a Variable Reluctance sensor just like the VSS.
Obviously the tooth count will be different.
Dakota Digital makes an interface to adjust pulses per mile to match input signal to speedo.
Here: http://www.dakotadigital.com/index....t_id=126/category_id=287/mode=prod/prd126.htm

You may be able to do that by reprogramming 4WABS module or GEM, but for $85 the SGI-5E Universal Signal Interface unit can be programmed by you fairly easily, vs getting a computer program or someone else involved and then involve again if there is a problem or other changes.

That's pretty interesting! I'm still running a very conservative, preliminary tune from my engine swap. I'll need to get it fine tuned on a dyno anyway, so hopefully my tuner can correct the speedo in a future tune. It's good to know there are other options if needed though. Thanks Ron!

 

[Blown]

A tuner can adjust the speedo/odometer easily based on wheel revolutions per mile and gearing, no problem. I got my speedo spot on with a recent axle swap from 4.10 ranger to 3.73 Explorer 8.8 (yay, disk brakes and limited slip).

An independent rear would be even sweeter!