Since my swap from automatic to standard I have not had 4 low.
Shifts fine into 4 high but wont go into 4 low.
I'm watching signals going to the ECM and FCM to see what its seeing and not seeing.
Need to know what you have to do to get the truck to shift into 4 low when you have a standard trans.
Clutch in?
Zero truck speed??
Idle speed?
Trans in neutral?
If I know what the modules are looking for them hopefully I can fool them.

 

Owners manual says transmission must be in neutral, vehicle stopped, clutch depressed, rotate switch to desired position.

 

Owners manual, brilliant. ;>)
So trans must have a neutral sensor. I should be able to fake that one.

Thanks

 

I'm wondering why you wouldn't bypass the computer and wire the transfer case functions directly. The switching sequence on OEM vehicles was designed-in deliberately to "idiot proof" the drive train and the easiest way for them to do this is through the computer with a few lines of code since the signals are already there for the most part. The easiest way to "clone" the intent of this design would be to use a couple of micro-switches to depict the neutral & stopped condition and to wire these up in conjunction with the HI/LO/NEUTRAL multifunction switch. Just off-the-cuff, I'd consider using a normally-on microswitch with the clutch pedal to provide the neutral condition and the same with the brake pedal to provide the stopped condition. If I was doing this, I'd want to lay out the schematic and make a list of all the driving conditions to ensure I didn't get into a condition where the t-case would switch when I didn't really want it to.

You could always consider making a small t-case controller of your own using a PIC or Arduino chip and use the speed signal to make a more bullet-proof switch condition selector.

 

That is an option and fairly simple to pull off but I'm so close to having it work like a stock system that I would like to try.
I found the clutch switch wire at the ECM and grounding it is recognized by the ECM as the clutch depresses. Stock speedo signal is working so all I should have left is the neutral sensor to fool.
Since I'm not the only person to drive this truck I like the idea of it being idiot proof, we are all idiots at some time. ;>)

 

Good quest EVguy, looks like you're almost there. There's a sticky on this forum pertaining to downloadable service manuals - if you don't already have a copy, you might want to get one and have a look through the wiring sections relating to the transmission and shifter harness

 

my 06 manual will shift in and out of 4lo while in gear. I like to shift it while barely rolling, clutch disengaged but in gear; I get a more positive shift that way.

 

That is very good news. Not having to deal with a neutral SW is a bonus.
I have the service manual that is online but its only up to 07 and the 08 truck is quite different. Fly by wire throttle is one of the differences and some wire colors are different.
The manual has been a huge help and most of the pin-outs on the plugs are correct, just different wire colors.
I'm heading to Portland in a couple of weeks to a shop that can reflash my ECM and FCM and hopefully make most of my problems go away.

 

On the downloadable parts list, I see that there's a neutral safety switch on the manual transmission - it's under Drivetrain Switches, fig 8-810. The name and description for that part don't make it very clear as to whether this is what you might want or if it's just the backup light switch.

 

In the service manual under transmission rebuilding it just shows the back up lamp switch so I would say its the only one.