G80 Tone Ring

LeedomtoFreedom · 11-11-2018, 06:45 PM

So I'm swapping diffs from both of my 240s, one with mechanical speedo, one with electronic.

The G80 I'm using into the car with electronic speedo has the 48 tooth but need the 12 tooth tone ring. Going through a couple threads and being extremely clever, I've realized that I need to cut some of those teeth out, but I was curious if there's anything to be mindful of.

If I grind down the unnecessary teeth, does the depth matter? I don't need to shim the sensor or anything.

cutting 2 out of 3 teeth. correct?

Really enjoying the electronic speedo, trying not to ruin it.

LeedomtoFreedom · 11-11-2018, 08:49 PM

Okay I took the tone ring off and manually removed the teeth using a pair of cable cutters (worked very well). I compared the diameter of the tone ring to the original and it seems to be slightly larger, which leads me to shimming the sensor slightly

Harry Tuttle · 11-11-2018, 09:54 PM

Quote:

Originally Posted by LeedomtoFreedom

cutting 2 out of 3 teeth. correct?

Is that what you did? In my universe that is not correct if you want 12. I leaves 16.

LeedomtoFreedom · 11-11-2018, 11:44 PM

After I compared the two, it's three of four teeth. Definitely throws the sensor way too close. The spec in the bentley manual is .85mm +/- .35mm for a 12 tooth sensor.

Wren · 11-12-2018, 08:30 PM

You need to use the G80-compatible differential cover and sensor to get the right clearance and location for the sensor. They are non-adjustable to my knowledge whereas the older 240 ones used shims.

LeedomtoFreedom · 11-13-2018, 12:33 AM

Yeah I realized that. I shimmed the sensor out using a washer with a 1 1/4" ID and had to grind down the outside (couldn't find one the right size) but a 1 1/2" OD. You check the clearance by shoving a feeler gauge through the oil fill hole. Haven't checked for operation but I'm guessing it will work. I also erred on the larger clearance to avoid the sensor being tripped by the diff itself, as the tone ring rides on metal.

LeedomtoFreedom · 11-14-2018, 05:42 PM

Tested and it works at about .9-1 mm clearance.

shoestring · 11-23-2018, 03:45 PM

Thanks for the update to the solution.

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11-11-2018, 08:49 PM	#2
LeedomtoFreedom Board Member Join Date: Oct 2017 Location: Chicago	Okay I took the tone ring off and manually removed the teeth using a pair of cable cutters (worked very well). I compared the diameter of the tone ring to the original and it seems to be slightly larger, which leads me to shimming the sensor slightly

11-11-2018, 11:44 PM	#4
LeedomtoFreedom Board Member Join Date: Oct 2017 Location: Chicago	After I compared the two, it's three of four teeth. Definitely throws the sensor way too close. The spec in the bentley manual is .85mm +/- .35mm for a 12 tooth sensor.

11-12-2018, 08:30 PM	#5
Wren Porkchop Sandwiches Join Date: Jun 2006 Location: Athens, GA	You need to use the G80-compatible differential cover and sensor to get the right clearance and location for the sensor. They are non-adjustable to my knowledge whereas the older 240 ones used shims.

11-13-2018, 12:33 AM	#6
LeedomtoFreedom Board Member Join Date: Oct 2017 Location: Chicago	Yeah I realized that. I shimmed the sensor out using a washer with a 1 1/4" ID and had to grind down the outside (couldn't find one the right size) but a 1 1/2" OD. You check the clearance by shoving a feeler gauge through the oil fill hole. Haven't checked for operation but I'm guessing it will work. I also erred on the larger clearance to avoid the sensor being tripped by the diff itself, as the tone ring rides on metal.

11-14-2018, 05:42 PM	#7
LeedomtoFreedom Board Member Join Date: Oct 2017 Location: Chicago	Tested and it works at about .9-1 mm clearance.

11-23-2018, 03:45 PM	#8
shoestring Board Member Join Date: Jun 2009 Location: Swampscott, 01907	Thanks for the update to the solution.