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Old 06-11-2017, 08:47 PM   #1
ZVOLV
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Default G80 speedo issues.

I installed a G80 into my 1990 240 without ABS. I trimmed the ring down from 48 window to 12 window as members here suggested. I used the original differential cover and I got NO Speedo operation. Just a little flicker here and there.




TODAY, I installed an aluminum G80 diff cover. Now my speedometer reads 60mph by the end of first gear!!!

What are my options here?









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Old 06-11-2017, 09:23 PM   #2
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What does the PROFESSIONAL LABSCOPE tell you?
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Old 06-11-2017, 09:32 PM   #3
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It said you are ugly.
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Old 06-11-2017, 09:35 PM   #4
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Maybe your car is just really fast.
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Old 06-11-2017, 09:37 PM   #5
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Nah, that's just pointing out the obvious.

Seriously though, you're always coming on here as the prophecy of expert advanced electrical engineering diagnostics with professional tools and what not. This one single issue you're having is a place where a scope would come in handy to see what's going on.

What am I missing here?
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Old 06-11-2017, 09:58 PM   #6
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There's a speedo calibrations thread floating around here, use a potentiometer to replace a single resistor on the speedo motor board and you can adjust the speed up and down.
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Old 06-11-2017, 10:12 PM   #7
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My guess would be that it's reading the G80 body as extra pulses. Try shimming the sensor further out?

If you can look at the signal in the scope and you have clean, evenly spaced pulses - you can get gadgets to resample those pulses at a fixed ratio and make the speedo read whatever you need it to.
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Old 06-11-2017, 11:01 PM   #8
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Subbed. Would like to see the solution for this.
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Old 06-11-2017, 11:21 PM   #9
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There are a different sensors. I had to space mine out with a washer as it was too close, hitting the trigger wheel even. Then it worked.
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Old 06-11-2017, 11:25 PM   #10
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Quote:
Originally Posted by Uncleknucklez View Post
There's a speedo calibrations thread floating around here, use a potentiometer to replace a single resistor on the speedo motor board and you can adjust the speed up and down.


This should be that thread: http://www.forums.turbobricks.com/sh...42#post5624342

I actually did connect a portable snap on labscope to it after the G80 install on the stock 1990 240 non ABS diff cover and got NOTHING! I was hoping the airgap was wrong and the aluminum diff cover would space it out properly, but it reads wayyy too fast.

Solutions that have been suggested to me have been to play with the gap, reverse polarity or the wires, try a different sensor, to possibly messing with calibration of the gauge.
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Old 06-11-2017, 11:35 PM   #11
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The earlier 90-91 type sensor that's a single blade instead of 2 works with 12teeth and and the aluminum cover. They used a similar, but slightly different aluminum cover 90-91. Sensor (different) mounts the same in either cover, 92+ cover has the magnet and oil filter built into it....


...




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Old 06-12-2017, 11:09 AM   #12
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When I installed a g80 in my 91 240 without abs, did exactly as you did and cut the teeth down to 12 but I had to space my sensor out with a washer. Everything has been working flawlessly since.
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Old 06-12-2017, 11:11 AM   #13
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I noticed this sensor had two blades. Year/model is unknown but it had that filter/baffle thing in it.

Which model can I get this sensor from? G80 in a 90-91 may be hard to come by....
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Old 06-12-2017, 11:40 AM   #14
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I still wonder if the G80 body is getting picked up by the sensor. I would try the spacing first, then the sensor type change. I bet if you scope it right now you'll see a very dense, very messy pulse train.
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Old 06-12-2017, 11:48 AM   #15
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I scoped the sensor before pulling it apart, just as practice, over a year ago on this car. I was able to capture a clean sine wave with increasing voltage and frequency with speed. It's the same as any ABS sensor that is NOT a hall effect.

I may just do some tests with a multimeter set to AC voltage or frequency.

I really hope I can find a sensor that will work with my new alum cover!
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Old 06-13-2017, 02:50 PM   #16
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I really hope I can find a sensor that will work with my new alum cover!
I really hope you do as well, I have an 86+ cluster in my 80, and have the 940 sensor in the aluminum cover, with a G80, and the tone ring cut the same as yours. I can't figure out why this wouldn't work, but it won't.

I still haven't tried to space it, I guess that should be my next stop. I just really need the signal for the mildly annoying high idle on occasion. I've really grown to like my digital speedo on my phone.
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Old 06-13-2017, 03:01 PM   #17
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Old 06-13-2017, 03:05 PM   #18
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Why did you grind all the teeth off the G80 and weld on a ring rather than just grind off the unnecessary teeth and use the aluminum cover and stock sensor? Seems silly.
I'm confused, there is another way to get all of these parts to work with a 240 speedo? I was firmly under the impression that a 940 sensor, on a 12 tooth ring (cut down G80 ring) and the 86+ 240 speedo would all play nice together?
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Old 06-13-2017, 03:25 PM   #19
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I removed the 48 tooth tone ring from the G80 and cut it down to 12 windows. I didn't grind the diff or weld anything. I just knocked the ring back in place.

The high idle is annoying and my MPG may be suffering too so I want to get this figured out.
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Old 06-13-2017, 03:25 PM   #20
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Originally Posted by Uncleknucklez View Post
I'm confused, there is another way to get all of these parts to work with a 240 speedo? I was firmly under the impression that a 940 sensor, on a 12 tooth ring (cut down G80 ring) and the 86+ 240 speedo would all play nice together?
I remembered incorrectly. I was thinking about the time I had to put an ABS open diff in a non-ABS 240. On that car, the tone ring is cast into the diff itself. There's not cage/ring to swap.

I thought he had ground off ALL the teeth, then welded a 12-tooth ring over top.
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Old 06-13-2017, 03:51 PM   #21
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The earlier 90-91 type sensor that's a single blade instead of 2 works with 12teeth and and the aluminum cover.


Labscobe

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So I need to find a 1990-1991 G80?!

That sounds tough. I'm gonna look around at the different setups and see what I can find, but the yards are getting pretty dry for RWD Volvo stuff. Anybody got one? Or at least a pic of what I'm chasing down here?

Thanks.
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Old 06-13-2017, 05:38 PM   #22
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I don't really get why you are jumping to needing a new G80.

Do you have a sensor which is correct for a 12 tooth ring? If not you may need to get one.

If you do have the 12 tooth sensor, is it correctly shimmed so that it is only picking up the teeth and not the G80 body?

Someone here can probably tell you what the "spec" clearance is. Your scope may actually be handy.

I think worst case is that you may need a tone ring which is different somehow - wider bars, thicker material, etc. I can't think of any reason replacing the G80 itself would be necessary.

I just hit up Google and found another thread where people have installed the tone ring the same way, and mention having to shim the sensor.

http://forums.turbobricks.com/showthread.php?t=306102
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Old 06-13-2017, 05:42 PM   #23
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No I don't think I need a new diff, I just am asking if I need to find a 1990-1991 G80 equipped vehicle to take the sensor from.

I guess I can play with the airgap, but there really should be a way to make this work.
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Old 06-13-2017, 06:31 PM   #24
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I could be wrong, but I think the important difference is whether it is a 12 tooth sender or a 48 tooth sender, and whether it has the collar style mount or the single bolt mount.

I did a lot of Googling just now and I can't find a part # for the particular combination you seem to need - 12 tooth with a single bolt mount. They are all listed as ABS/48 tooth (1398321) or have the collar mount (1308024).

KJet says that one exists, and I trust him on that. It might be NLA. I doubt that it is different for the G80 cars but they may have come with a factory shim of the correct size.

The alternative I can think of is to get a 48 tooth tone ring back on there, shim correctly, and purchase/build a "pulse divider" to cut the number of measured pulses in 1/4 between the sensor and the speedometer - effectively "translating" your signal to something the speedometer knows how to read.

It may be possible to use the 48 tooth sensor with the 12 tooth ring, but I don't know enough about how the sensors differ to tell you.
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Old 06-13-2017, 07:44 PM   #25
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The G80 cover I have is already from 1991 740 Turbo, I think....

The sensor was dual blade and mounts via one bolt.

Last edited by ZVOLV; 06-13-2017 at 09:12 PM..
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