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Transmission Tachometer Transducer
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Supporting Member of Barthmobile.com 1/21
Picture of Pirate19
posted
Trying to locate the tachometer transducer, "sending unit", on my 5.9 Cummins, Allison AT542, 4 speed tranny. Might the indicated, mounted in the forward/input end of the housing, be the piece. Thanks.


'92 Breakaway
Cummins 190hp, No Modifications
Allison AT542
Floor Plan 30-BS-11B
9205-3798-30BS11B


 
Posts: 297 | Location: USA | Member Since: 11-07-2014Reply With QuoteReport This Post
Supporting Member of Barthmobile.com 10/08
Picture of MWrench
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That is where mine is located (looks the same also) but I have a MD3060 6 speed trans.

Don't think that make a difference


Ed
94 30' Breakaway #3864
30-BS-6B side entry
230 Cummins, Allison 6 speed
Spartan chassis
K9DVC
 
Posts: 2210 | Location: Los Gatos, CA | Member Since: 12-08-2005Reply With QuoteReport This Post
Supporting Member of Barthmobile.com 4/08
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Same here. It's on the engine not the transmission.


'92 Barth Breakaway - 30'
5.9 Cummins (6B) 300+ HP
2000 Allison
Front entrance
 
Posts: 1104 | Location: Minneapolis/Yuma | Member Since: 08-17-2006Reply With QuoteReport This Post
Supporting Member of Barthmobile.com 1/21
Picture of Pirate19
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Thank you gentlemen. And I imagine it functions by sending an electrical pulse from a magnetic origin, similar to the old style cruise control sending unit.


'92 Breakaway
Cummins 190hp, No Modifications
Allison AT542
Floor Plan 30-BS-11B
9205-3798-30BS11B
 
Posts: 297 | Location: USA | Member Since: 11-07-2014Reply With QuoteReport This Post
Supporting Member of Barthmobile.com 1/21
Picture of Steve VW
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Most of the older style sensors consist of an inductive coil which indeed generates a pulse of current when a magnet passes by. These are usually simple to troubleshoot, as the sensor is a sealed coil with two leads. The coil resistance can be measured with an ohmmeter and will have a specific resistance. Open or shorted coils will show higher or lower resistance respectively.

Newer designs are often based on Hall effect sensors. Hall effect sensors are semiconductors of the FET (field effect transistor) type. They usually have three leads, or two leads plus ground. The sensors respond to a magnetic field by changing their conductivity. An applied voltage allows current to flow through the sensor when in the presence of a magnetic field. They usually have a power lead, ground lead and a sense output lead. These are more difficult to diagnose since they consist of semiconductor diodes, not easy to check with standard meters. Common applications include crankshaft sensors and keyboard sensors.

I am fairly certain the Allison transmission sensors are of the older inductive coil type.


9708-M0037-37MM-01
"98" Monarch 37
Spartan MM, 6 spd Allison
Cummins 8.3 300 hp
 
Posts: 4373 | Location: Kalkaska, MI | Member Since: 02-04-2011Reply With QuoteReport This Post
Supporting Member of Barthmobile.com 1/21
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I think it is the inductive coil type with the two leads. I understand fully open reads 1, and shorted very close to 0 resistance. Would it be unusual to be partially open or partially shorted? Meaning if not 1 or near 0 then probably a good sensor. I have no idea what the proper resistance is for a good sensor.


'92 Breakaway
Cummins 190hp, No Modifications
Allison AT542
Floor Plan 30-BS-11B
9205-3798-30BS11B
 
Posts: 297 | Location: USA | Member Since: 11-07-2014Reply With QuoteReport This Post
Supporting Member of Barthmobile.com 1/21
Picture of Steve VW
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Correct. Prob a couple hundred ohms normally. Sometimes they are intermittent when they heat up.... Thumbs Up


9708-M0037-37MM-01
"98" Monarch 37
Spartan MM, 6 spd Allison
Cummins 8.3 300 hp
 
Posts: 4373 | Location: Kalkaska, MI | Member Since: 02-04-2011Reply With QuoteReport This Post
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what we are talking about here is a "hall effect sensor" You can google it or go here---https://www.electronics-tutorials.ws/electromagnetism/hall-effect.html They are quite commonly used to sense proximity of ferromagnetic objects. and have been around for years (nearly back to the vacuum tube days. By nature they are extremely reliable, the unreliable part comes in when the cheapest offshore source is used to reduce cost and to enhance the dealer repair income. Because of this they are quite overpriced to the consumer. john
 
Posts: 76 | Location: golden valley, az | Member Since: 02-05-2009Reply With QuoteReport This Post
Supporting Member of Barthmobile.com 1/21
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Why don't we have a saluting emoji? My point made... and with no drift intended.


'92 Breakaway
Cummins 190hp, No Modifications
Allison AT542
Floor Plan 30-BS-11B
9205-3798-30BS11B
 
Posts: 297 | Location: USA | Member Since: 11-07-2014Reply With QuoteReport This Post
Supporting Member of Barthmobile.com 1/21
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Salute


#1 29' 1977parted out and still alive in Barths all over the USA

later: 25' '82 Euro 70% ready for the road (if I can find the fountain of
youth) it is somewhere here in central
FLA



 
Posts: 1083 | Location: Floral City FL | Member Since: 04-25-2008Reply With QuoteReport This Post
Supporting Member of Barthmobile.com 1/21
Picture of Pirate19
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Like looking for something in the fridge. My wife's selfi - Mad


'92 Breakaway
Cummins 190hp, No Modifications
Allison AT542
Floor Plan 30-BS-11B
9205-3798-30BS11B
 
Posts: 297 | Location: USA | Member Since: 11-07-2014Reply With QuoteReport This Post
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