Aftermarket trans. cooler install

[a bear]

On edit: I had originally started this thread when I needed help from the Helms Manual. Since this led to a mod I'm trying with the tranny cooler I went ahead and changed the subject title to relate better to where the thread went. (my fault)
It may die anyway but at least the title now fits.

Thanks Bill!


Can someone with a 2002 or equal Helms manual help me locate the tranny temp gauge input wire which is in the 24 wire plug behind the gauge cluster. There are 24 wires in the plug. (Two rows of 12)
Guess nows a good time to quit putting off the inevitable and invest in the manuals.

[ 08-23-2005, 04:15 AM: Message edited by: a bear ]

[DmaxMaverick]

It doesn't appear there it a temp signal wire. The diagram I have shows the signal coming from the logic circuit. This means it is through the serial bus, which also controls the tach and speedo. The connector does not show a wire specific to the tranny temp. The volt meter and oil pressure are the only traditional gages, that receive an actual signal from the senders.

The tranny sends the temp signal to the TCM, and the TCM sends it to the PCM/ECM, where it is part of the logic circuit, which is decoded by the logic board in the I/P.

What's the reason for needing it? If you need to access the senders signal, you'll have to do it at the tranny.

[a bear]

Thanks Dmax Maverick,
You just confirmed my suspicion. I was lookimg for an input to send a signal to a Spal PWM fan controller to switch on/off and variably operate fan speed for my tranny cooler and was getting a bunch of squirrely readings at the gauge harness. I can get good readings at the Allison input wire, but this input also controls shift solenoids in the tranny via the TCM to disable some shift functions on a cold tranny. (Below 120 degrees) I was afraid this was a logic controlled gauge. The Spal controller would work above 120 degrees, but between anbient temp and 120 where the OD shift function is disabled the fan will run constant at 100 percent due to low sender voltage and may not allow the tranny to warm up. Once past 120 degrees everything can be cycled trouble free at selected temps. I guess now I will need to purchase a temp switch that will disable the Spal fan controller below say 150-160 degree.

Thanks again,
Tommy smile.gif

[DmaxMaverick]

Even if it were an analog gauge, it would be a bad idea. Adding load onto a linear circuit will either overload it, or make both ends inaccurate. What you need is a switch. Shouldn't be too hard or expensive to do.

[a bear]

According to the schematic the fan controller is only reading the temp sensor voltage. The load is coming from a separate control circuit with its own 12V supply/relay. Per the wiring diagram 12v is sent from the battery to the fan via the power supply relay. There is also a wire from the ignition that powers the controller.
I know enough about electrical components to get me into trouble so if you see something that I'm missing please set me straight. Thanks for the input.

On edit: Here's some of the information on the controller.

Specific Product Info...
Fans (Pull) - Spal Fan Controller - Pulse Width Modulation Control Module
Vehicle Performance > Engine Performance > High-Performance Fans > Fans (Pull)
By: SPAL
MSRP: $93.00
Just: $60.00 Each
Description:
Controls Up To 2 SPAL Fans

[a bear]

Ok I think I see where I caused a misunderstanding. Hope this explains things better. What is happening with the system is that the OEM tranny temp sensor runs on a 0-5 volts DC signal. Untill the tranny is warmed up to 120 degrees the signal is running at <1.6 volts. I expect the PCM/ECM is taking into account what the tranny is doing and makes the corrections for the factory temp gauge to read correctly below 120 degrees. Once the tranny reaches 120 degrees and the solenoids normalize the readout will immediately jump up from 1.6 to 3.70 volts and afterwards the voltage will begin to drop according to temp as follows. About .25 volts for every 10 degrees.
3.70 @ 120 degrees
3.45 @ 130 degrees
3.21 @ 140 degrees
2.96 @ 150 degrees
2.71 @ 160 degrees
2.47 @ 170 degrees and so on
For example: If I set the controller to start the fan at 150 degrees or 2.96 volts. This would start the fan at 50 % speed. Then if I set the high limit at 170 degrees or 2.47 volts this would run the fan at 100 % speed. Anything in between would increase the fan speed variably according to the higher temp/voltage drop. The higher the temp the lower the voltage and the higher the fan speed which is good.
Where the problem occurs is when the tranny is lower than 120 degrees and voltage is <1.6 volts due to the sensor concurrently controlling the tranny functions. This would cause the fan to run at 100% and lengthen/prevent tranny warm up because the controller sees the lower voltage as higher temps. This is why I was hoping to capturing a more linear signal below 120 degrees at the factory gauge. Unfortunately the signal here is dictated by the PCM and is not a usable signal. A temp switch to disable the fan controller below 140 to 150 degrees should do the trick.

[ 08-21-2005, 05:42 AM: Message edited by: a bear ]

[a bear]

Well after lengthy thought, considering information provided by the tranny documentation and the input from DmaxMaverick I've decided to get away from the OEM temp sensor all together. The temperature values are simply used too much by the TCM to make it a good choice for another function. I've now decided to go with the recommended Spal sensor. Once this project is complete I will post a follow up for those few that are interested in installing their cooler below the stack to help out with temps and fan clutch activity. Hopefully while the weather is still hot.

Tommy

[jbplock]

Originally posted by a bear:
... Once this project is complete I will post a follow up for those few that are interested in installing their cooler below the stack to help out with temps and fan clutch activity... Tommy,

Sounds like another first class set-up http://forum.thedieselpage.com/ubb/icons/icon14.gif ... looking forward to hear the details ...

smile.gif

[a bear]

Thanks Bill,
I will post the results.(Good or bad) Since I've already experimented with removing the cooler from the stack in a less elaborate experimental setup I can say that very positive results were realized. GM may have realized this also because as I understand it the 06 models have their coolers relocated. It's also worth noting that this mod may not be for most out there but for those that generate a lot of heat from trans mods,heavy towing and/or stop and go city driving there will be a measurable benefit.

Maybe this needs to be in a new thread. It now has nothing to do with the Helms Manual so I guess it's way off topic. Is there any way to change the title?

[ 08-22-2005, 01:36 PM: Message edited by: a bear ]

[jbplock]

Originally posted by a bear:
Maybe this needs to be in a new thread. It now has nothing to do with the Helms Manual so I guess it's way off topic. Is there any way to change the title? Tommy,

A new topic would probably be best but you could also try editing the title in your first post. I opened it and the title didn't seem to be locked from editing.

smile.gif