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Need Help With Engine RPM Signal For TCM

M

mynewtoy

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Barrman said:
I forgot about the oil pump drive way. I had one of those and tried it first. It leaked oil out of the plug housing when I test ran the engine. Then my serpentine belt drive vacuum pump froze up soon after. I went with a CUCV vacuum pump and promptly forgot all about the speed sensor back there. The Dakota Digital converter box for the alternator signal was a lot cheaper than a replacement cam drive tach signal generator and I haven't looked back.
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Barman Thanks! I never thought about the sensor leaking oil. I'm glad you mentioned it. I can get one from AutoZone my cost is 235.00 and then I have to worry about future failure and oil leak I'm going to look into the alternator tach signal and convertor box. I suck at electrical but I'll have to learn my way through it.
Thanks Everyone For Your Input
Barman Do you have a 4L80E in a CUCV ?
 
M

mynewtoy

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Kiethj
I looked at my truck my alternator has that exact wire that your pointing to in your picture. Do I just cut the wire at the harness? That won’t affect anything to do with the way the truck charges?
 
Keith_J

Keith_J

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mynewtoy said:
Kiethj
I looked at my truck my alternator has that exact wire that your pointing to in your picture. Do I just cut the wire at the harness? That won’t affect anything to do with the way the truck charges?
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No need to cut it off, just unplug and tie off. This terminal is provides an alternating current signal for the test port under the dash by where the civi radio would be. As Barrman stated, for the STE-ICE diagnostic tool. The only wires necessary for charge are the two wire plug and the positive and negative fat wires.
How the tach terminal works is it supplies alternating current at varying frequency which is proportional to engine speed.
 
M

mynewtoy

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West Pittson Pa.
Keith_J said:
No need to cut it off, just unplug and tie off. This terminal is provides an alternating current signal for the test port under the dash by where the civi radio would be. As Barrman stated, for the STE-ICE diagnostic tool. The only wires necessary for charge are the two wire plug and the positive and negative fat wires.
How the tach terminal works is it supplies alternating current at varying frequency which is proportional to engine speed.
Click to expand...
Forgive me for sounding stupid but wouldn’t I need the terminal end that attaches to the alternator to run the wire to the Dakota digital converter box? I didn’t take the tach wire off the back of the alternator yet but it looks like a special type of connector. That’s why I asked if I could cut it so I could extend it to feed the Dakota digital converter. Or is there a terminal end that will fit on the back of the alternator if so I won’t cut the harness.
 
Keith_J

Keith_J

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mynewtoy said:
Forgive me for sounding stupid but wouldn’t I need the terminal end that attaches to the alternator to run the wire to the Dakota digital converter box? I didn’t take the tach wire off the back of the alternator yet but it looks like a special type of connector. That’s why I asked if I could cut it so I could extend it to feed the Dakota digital converter. Or is there a terminal end that will fit on the back of the alternator if so I won’t cut the harness.
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I traced this wire to inside the cab, branching off to connect to the Dakota Digital module for the tach signal. I forget where under the dash..
 
Barrman

Barrman

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I have a 4L80E in a 1987 Suburban that looks like a CUCV. I can’t think of anything different between them concerning 4L80E installation.
 
Keith_J

Keith_J

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The stock 4L80 transmission has the input speed sensor on the forward clutch. I have heard of some transmission where it is moved to the pump. The pump is driven off the torque converter shell so it is the same as the engine speed.

I know TCI controllers need engine speed sensor.
 
M

mynewtoy

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West Pittson Pa.
Keith_J said:
The stock 4L80 transmission has the input speed sensor on the forward clutch. I have heard of some transmission where it is moved to the pump. The pump is driven off the torque converter shell so it is the same as the engine speed.

I know TCI controllers need engine speed sensor.
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Mine is actually a 4L85E pulled from a 2007 2WD bus behind the Duromax. It has two sensors on the side of the case. Is one the input speed sensor and the other the output speed? sensor
 
Keith_J

Keith_J

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mynewtoy said:
Mine is actually a 4L85E pulled from a 2007 2WD bus behind the Duromax. It has two sensors on the side of the case. Is one the input speed sensor and the other the output speed? sensor
Click to expand...
Front is TISS, rear is TOSS. That may or may not work as post 1998 models use integration between the engine and transmission via controller area network bus (CAN buss). Beyond my pay grade to know specifics.
 
Barrman

Barrman

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I have the Compushift controller. It doesn't need a tach input to work but it does need one to show rpm on its display. I also have a Dakota Digital gauge cluster which does need a tach input. So, I have the TCM and the gauge cluster both getting the signal from the Dakota Digital converter box which gets it from the alternator.

I did have a problem with that a year or so ago. I was driving along nice and happy and noticed my rpm was 2500 but my road speed was 60 and I was in 4th with the converter locked. 2000 rpm is normally 70 mph. I was 30 miles from home on a cold dark night. I kept slowing down and slowing down with visions of a burned up transmission in my head. Turns out my alternator pulley had broken at the bolt. The inside of the pulley was gone and the outside of the pulley just happened to not fly off. The reduced diameter caused a faster spinning alternator and therefore a higher rpm read out.
 
M

mynewtoy

Member
65
2
8
Location
West Pittson Pa.
W
Barrman said:
I have the Compushift controller. It doesn't need a tach input to work but it does need one to show rpm on its display. I also have a Dakota Digital gauge cluster which does need a tach input. So, I have the TCM and the gauge cluster both getting the signal from the Dakota Digital converter box which gets it from the alternator.

I did have a problem with that a year or so ago. I was driving along nice and happy and noticed my rpm was 2500 but my road speed was 60 and I was in 4th with the converter locked. 2000 rpm is normally 70 mph. I was 30 miles from home on a cold dark night. I kept slowing down and slowing down with visions of a burned up transmission in my head. Turns out my alternator pulley had broken at the bolt. The inside of the pulley was gone and the outside of the pulley just happened to not fly off. The reduced diameter caused a faster spinning alternator and therefore a higher rpm read out.
Click to expand...
Wow that’s crazy! I wish I was better at understanding wiring so I could figure this out I’m hoping once I get the Dakota Digital rpm box the instructions will clear things up.
 
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