AM gauge cluster install NOW- no Speed Sensor Signal to ECM

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Jwernatl

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Senoia, GA
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Truck Year
1987
Truck Model
V10
Engine Size
5.7ltr
Guys and Gals - thanks to Turbo Dog and Edward Koleman and a few others - I've got the cluster installed. It's not as user friendly as they market and advertise. but I've learned a lot - some of which was 20/20 hindsight.

Yes, I've had some trials and tribulations.

And still, actually have a few. the main issue I have right now has to do with the TCC lock up.

When following the install directions for the speedometer it's very cut and dry -

In the kit (with the GUAGE CLUSTER) they give us a 'pulse signal generator' that connects direct to transmission speedometer gear housing, which directly wires directly back to the speedometer -

I'm now realizing that I've 100% bypassed the original speed sensor, which sends a signal to the ECM -and that mainly controls the operation of the TCC system, shift light, and cruise control.

Im going to call tech support on Monday BUT I've got ALL day tomorrow to work on this - anyone know what I need to do?

I've been reading lots in the drivability manual below -

http://www.mediafire.com/download/i...Fuel_and_Emissions_Including_Driveability.pdf

AUTOMATIC TRANSMISSION TCC System The Transmission Converter Clutch (TCC) System, used on a 7004R transmission, uses a solenoid operated valve, in the automatic transmission, to couple the engine flywheel to the output shaft of the transmission through the torque converter. This reduces the slippage losses in the converter, which increases fuel economy.

If the converter clutch is applied at all times, the engine will stall immediately, just as in a manual transmission with the clutch applied. If the converter clutch does not apply, fuel economy may be lower than expected. If the Vehicle Speed Sensor fails, the TCC will not apply
.

The ECM completes a ground circuit to energize a TCC apply solenoid in the transmission which moves a check ball in a fluid line (Figure 10-1).
This allows the converter clutch to apply, if the hydraulic pressure is correct, as described above.

The ECM controls the TCC apply solenoid by looking at several sensors:

• Coolant Temperature Sensor. Engine must be warmed up, before clutch can apply.
• Throttle Position Sensor (TPS). After the converter clutch applies, the ECM uses the information from the TPS to release the clutch, when the vehicle is accelerating, or decelerating at a certain rate.

• Brake Switch. This switch in the TCC circuit opens, when the brake pedal is depressed. This degenergizes the TCC solenoid.


• Pulse switch. This is a downshift 4-3 pulse switch, which opens the TCC solenoid c irc u it, momentarily, during a downshift.


Again, everyone - has anyone installed this? or maybe an aftermarket speedo?? - what did you do about sending a Speed sensor signal to the ECM?

I've got ALL day tomorrow to work on this - anyone know what I need to do?

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Jwernatl

Full Access Member
Joined
Oct 5, 2020
Posts
190
Reaction score
127
Location
Senoia, GA
First Name
John
Truck Year
1987
Truck Model
V10
Engine Size
5.7ltr
Well look what I found!

I think this is what I need.... Sorry for the long read above....
 

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  • SN74 Speedometer Calibration Module_RevD.pdf
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