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Old 05-08-2012, 07:33 PM   #1
icwbmx
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Default Modifying speedo for use with t5

So as i understand it i can "calibrate" a stock 240 speedo by changing the resistance between pin 4 and 13.

My question is will the speedo work off an 8 pulse or a 16 pulse sender unit? Would one be better than the other?

And how would the speedo gears come into play?

Thanks
IAn
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Old 05-08-2012, 07:37 PM   #2
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You've got an electronic speedo in your '83?

I've heard of people using a T5 speedo cable and changing the fitting at the speedometer end.
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Old 05-08-2012, 08:18 PM   #3
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Well i have a cable driven (85mph) speedo in there now, but i have an electronic (120mph) one laying around.
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Old 05-08-2012, 08:21 PM   #4
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There is a VSS available for the T5 that will generate an electronic signal proportional to speed. With that in the speedo cable hole you should be able to fashion a circuit that will let the speedo talk to the VSS.
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Old 05-08-2012, 09:13 PM   #5
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Didn't Sean (hackster) just do this by putting a electronic speedo from a later car in and using the 2.4 speedo pickup/diff cover? I remember just seeing the thread.

I suppose this would require the tone ring but if you were swapping to a g80 anyway...
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Old 05-08-2012, 09:23 PM   #6
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Is the VSS much different from the pulse generator such as this one http://www.ebay.com/itm/Ford-speedom...r#ht_596wt_954 ??

I was thinking of just using the stuff out of a late 240 but it would just be too much work. especially since I just swapped in an axle with a welded diff custom solid bushings.
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Old 05-09-2012, 07:59 AM   #7
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Not sure -- the one I'm referring to is designed to go into the opening in the T5 manual tranny where the speedo cable would normally go. On the Mustangs the VSS sent a signal to the ecu that was used for various things and also used for cruise control function. The VSS had the plastic gear that went into the tailshaft housing on the T5 and then the speedo cable plugged into the VSS. Of course, if you're using an electric speedo then there's no need for the cable... Looks like this....scroll down when you get to the page. http://www.partstrain.com/store/?N=0...Speed%20Sensor)
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Old 05-09-2012, 08:54 PM   #8
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Yah I think we are talking about the same thing.

I called a local transmission/driveshaft shop today. The owner said if he has any in laying around in the back I can have one. Ill try it out and see if I can get it all sorted out. It's a pretty simple/cheap solution if it works.
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Old 06-11-2012, 03:32 PM   #9
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Works like a charm.

So what i did was:
1. Install a mustang speedo sender (one with an electric cruise output) into the tranny with a gear set that was somewhat close.

2. Wire up the cruise control output to the volvo speedometer the same way the stock volvo speed sensor would be wired. (Diagram can be found in the back of any haynes manual.)

3. Then calibrate by way of a potentiometer. See thread below. http://forums.turbobricks.com/showthread.php?t=239021


I havnt had a chance to drive the car and fully calibrated it yet but with the rear jacked up it was giving me rock solid readings. Much nicer than the jumpy cable driven m46 speedo.

Thanks
Ian

Last edited by icwbmx; 06-17-2012 at 05:02 PM..
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Old 06-11-2012, 06:06 PM   #10
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Can I swap a 120 mph electric speedo from a later model Volvo into my 82 cluster - and then make the switch? I already have magnets/pickup on the driveshaft for a cruise control - wonder if I can use that output to make the electronic speedo work.

I have questions about calibration -- I'll ask them in the other thread; it's an old one - I wonder if JW240 is still subscribed? Hmmm....

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Old 06-11-2012, 06:11 PM   #11
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Yah, that's pretty much wat I did. Swapped a late model 120mph speedo into my '83 cluster.
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Old 06-11-2012, 06:20 PM   #12
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Ah - we'll need to talk. Would you mind taking a look at the thread you linked -- you may be able to help answer my questions.
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Old 06-11-2012, 07:02 PM   #13
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Hmm-I have to hack up my early cluster to fit an electronic speedo in the back anyhow, and I've got a later T5 with the electronic speedo out already. I wonder if wiring up that speed sensor would be any easier or harder than using the one in the 3.73 axle that'll be going in soon...
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Old 06-11-2012, 07:05 PM   #14
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Seems to me the biggest difference is this -- if using the 3.73/tone ring/sensor will allow the speedo to work accurately without calibration -- that's easier than using the T5 hardware and having to recalibrate.

My speedo is off with my new tires -- and I was going to use a simple speedo gear change to fix it -- but there may be a better mousetrap available.
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Old 06-11-2012, 07:07 PM   #15
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I'll be putting in a G80 from a car that I forgot the axle ratio of, and in order to use the 240 speed pickup, I'll have to mod the tone ring on the G80 by grinding off a bunch of teeth. I'll have to see whats up with the tone ring in the axle when I pick it up, and see if the tone ring on the G80 can be converted.
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Old 06-11-2012, 07:31 PM   #16
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Ah - well, this may be the situation dreamed of when the phrase '6 of one, half dozen of another' was coined...
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Old 06-11-2012, 07:51 PM   #17
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Check out http://cleanflametrap.com/speedo.html for some more info about the electronic speedo.
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Old 06-11-2012, 08:14 PM   #18
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Really struggling here - at that link I see the same discrepancy between units. There are 2 that both have what appears to be a metal cylinder of some sort -- is that behind and above the actual gauge? I think I can see the needle on the top pic. Where is all that relative to the white plastic thingy where JW240 shows the resistor(s) going in?
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Old 06-11-2012, 08:55 PM   #19
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What you see in the pics is the back of the actual gauge. the white plastic thing is part of the cluster board. remove the screws from the back of the cluster and the whole back "board" will separate from the black housing. then the gauge will come out of that if you remove the small screws located on the white plastic piece. I will take pictures in the next day or two and better illustrate the process.
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Old 06-11-2012, 09:47 PM   #20
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'Preciate it....
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Old 06-11-2012, 10:44 PM   #21
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otherwise if you go full custom. and autometer speedo can be wired right into the electric mustang sender as well!
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Old 06-11-2012, 11:07 PM   #22
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Perhaps at some point - but I have a full compliment of Volvo/VDO gauges that all work properly with the Ford engine. Like to stick with that.
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Old 06-17-2012, 01:48 PM   #23
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ok from the top...

Picture of the back of a 240 cluster removed from car. Remove the 7 screws along the outter perimeter.

Remove the brown board from the plastic housing.


To access the back of the speedometer remove the 4 screws from the plastic casing.



From here you will be able to see the calibration resister. I just cut the resistor off and soldered in thin gauge wire with a variable resistor on the end for easy calibrating.
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Old 06-17-2012, 02:02 PM   #24
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smmmarrtttyy pants! thats clever!
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