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Explorer 8.8 VSS to 240 Speedo

volvowagoon

Active member
Joined
Jul 19, 2012
Location
Franklin, IN
I'm sure that there aren't many if any people on here who have thought about this, but I'm determined to keep the factory gauges in my '89 240. I think the speedometer is going to be the biggest pain in that though.

If I am not mistaking, the original gear ratio in my car was 3.31:1. I have an automatic wagon if that helps. The new Ford unit I'm guessing is a 3.73:1 because the VSS only comes on the differential if the Explorer is 2WD. A rough estimate by look spinning the rotor once and counting the pinion rotations indicate closer to this than the 3.27:1 ratio from a 5-speed.

Weren't there 240s with factory 3.73s? If so, does anybody know what speedometer was used with it and if it was electric?

Of course, there are other factors. I don't know how the Ford sensor operates other than that it's a VR. I haven't counted the reluctor wheel teeth or measured distance between wheel/sensor on either of the rear ends yet to see, but I'm hoping somebody knows enough to say "yeah it's easy" or "not worth your time" before popping the new dif cover off again.

I know that I didn't offer a lot of solid information, but I was mostly hoping to find somebody who has been through this already. Otherwise, I will attempt to be a pioneer! Thanks everybody.
 
Dakota Digital offers an electric speedometer adapter/controller/signal manipulator thingie. Sounds like it's what you want to use.
 
The gear ratio doesn't matter. The sensor reads the rotations of the diff carrier/axles directly. Gearing only matters when you're 'upstream'. At the diff, all the gearing is already done.

What really matters is how many triggers per rotation. If you can get the same number as the Volvo axle uses, you're good.
 
^ Before you buy anything, pull the cover on the Ford diff and count the teeth. I seem to remember them being 40+ teeth.
 
Ahh yeah... brain fart. The ring gear is going to spin at the same speed regardless of ratio. I didn't bring wheel size into play though. My new ones will be bigger and there is no use going through too much trouble for a wrong signal. The Dakota Digital universal signal interface is probably my best bet if I want to do it right.

How many teeth are there on the Volvo?
 
12, what ever ABS is (24 or 48?), and I think another one. Definitely significantly less than what the Ford 8.8 used (at least the truck ones that I have been into).
 
I found 49 and 50 tooth wheels on Summit. I guess that's the job for the signal interface. I'm reading the manual for that controller you talked about, and it seems like a really helpful piece!
 
You could also just get a GPS speedometer. That might fit into a gauge cluster, maybe.
 
If you can get the speedo to read the signal coming from the diff, even if it's WAY off you could just replace the resistor that calibrates the speedo with a pot and adjust as needed. I have a 0-100 ohm installed and it is enough to wildly change the speedometer calibration.
 
lol maybe if 130, 50, 49 or whatever it is was divisible by 12 that would work. Otherwise, the needle will bounce, and that would annoy the **** out of me.
 
http://forums.turbobricks.com/showthread.php?t=239021
https://www.brickboard.com/RWD/volvo/853622/740/760/780/ringlee_calibrate_speedometer.html

Is there I got my info to swap out the resistor for a pot. You could also temp install the pot and tweek it until your speedo is dead on with a GPS or something and then remove the pot at it's current setting and replace it with an equal value resistor.

I don't think you need to mess with the ring at all if you can bring the speedo into calibration by adjusting the value of the resistor.

Photos here also of how somebody ran the wires for the pot.
http://forums.turbobricks.com/showpost.php?p=4213487&postcount=23
 
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Just remember, I don't think this will keep your trip/odometer in check. They will continue to be off by the % that you deviated from the original resistor value. If you want the trip/odometer AND speedo to be dead on you need to fabricate a new ring like Lord_Athlon said. I have also read about cutting the ring off of a Volvo diff and welding it onto the ford 8.8" unit and then slightly adjusting with a pot. Let me see if I can find that.

This isn't about a ford unit but you may be able to do something like this.
http://www.davebarton.com/volvorearends.html

Some more info about the tone ring and peoples fixes
http://forums.turbobricks.com/showthread.php?t=204882
http://forums.turbobricks.com/showthread.php?t=280512

Here is a 108 tooth tone ring for the ford 8.8" axle. You could cut the teeth again like Lord_Athlon said to bring you down to an even 12
http://www.yukongear.com/ProductDetails.aspx?ProdID=1889
 
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Ahh well that changes everything. I want the odometer to work too. I should have remembered that those two work semi independently. I guess I will look into tone ring mods.
 
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