'97 K2500 front 4x4 differential engagement options?

[schiker]

Dang just when I really want my 4x4 to work the front differential did not engage. Like there is a good time for your 4x4 not to engage at least I was being proactive and tried it before I was stuck. I haven't investigated it yet except that transfer case operates in 4LO and 4Hi just doesn't engage front end. I assume its the electric heated gas operated pull mechanism is bad.

Isn't there a later updated servo mechanism and the manual pull cable system as options for differential lock. What are your opinions of these?

How hard is it to change out any special tools?

 

[THEFERMANATOR]

GM only carries the updated 98+ style electric motor actuator. They are very reliable, and you rarely hear of them failing. You have to run 1 wire to a keyed on positive feed for the power feed to the motor, but other than that it is a drop in install that takes less than an hour to do including running the power wire to it. The manual cable is another option for close to the same money that many have used. Another option is if your in 4X4 alot, you can buy the auto 4X4 plug that goes in and locks the front end in all the time. I don't reccomend this for vehicles that don't run in 4 wheel drive alot.

 

[ak diesel driver]

I bought mine along with a wiring harness off rockauto

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[schiker]

Can you explain that wiring a little. I see the actuators that have 5 pins and a separate harness and connector 5? wires. Do you use the existing wiring to some of the pins and then add 12V power line. How many amps can it draw and suggested fuse if needed? What is the typical power source for keyed power for it?

With the updated actuator the transfer case still activates when it engages or do you add a switch? Can you add a 3? position switch for cab control? So it could be disengage/ off / engage? or maybe it just needs engaged/disengaged 2 position switch?

 

[ak diesel driver]

IIRC the harness was plug and play with the exception of a brown wire tied into the transfer case wiring. I thought it was a ground tho...

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[625fireman]

I would opt for the manual setup. I will be going this route when gives up..

 

[THEFERMANATOR]

IIRC the harness was plug and play with the exception of a brown wire tied into the transfer case wiring. I thought it was a ground tho...

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It's al plug and play except for the brown wire that is tied into a keyed on 12 volt power source. The old style 97- actuators only got power when on which caused a piston to run out because of the thermal setup. The 98+ style uses an electric motor that runs a piston in and out. So it needs 12 volts to be able to retract the piston when it is not needed. I've wired a few of these up now. GM reccomends running it back down the engine to the transfer case wiring, but I normally extend it out and run it with the other wires rather tahn having one stray wire run.

 

[schiker]

Thanks, its starting to make sense. I saw a picture of the GM wire harness and it does look much more plug and play. The generic pictures on a few parts house websites just showed one end with the harness connector and had some white wires for splicing. That left a whole lot of questions for me. The GM harness has ends for connecting to existing wiring and a long brown wire to attach back to transfer case wiring or other source.

Decisions decisions. I like the clean look of the GM fix but its a nice feature to have 4lo and not engage front with posi lok (especially when I want to creep backwards in reverse backing a trailer with the 5 speed). I am worried about corrosion and mud on the posi lok over time if it will get harder to engage or stick and any sealing issues with mechanical actuation rod/mechanism?????

I guess I will google for some more stories and testimonials. If you see any or have long term install story post it.

 

[schiker]

I have been thinking about this and seems it should be easy to make an interrupt switch for the new style servo motor.

What about this I assume it works like the reverse lights..... There is a power wire (key on) that goes to the transfer case that when you shift to 4x4 it closes a limit switch and sends power to the front thermal linear actuator to engage differential. Once the actuator fully strokes it closes another limit switch to send power to light the front differential is engaged indicator.

The new one has same 4 wires plus a new 5th wire to disengage the front differential. Which is probably has a normally closed switch inline that opens when the stroke to engage wire has power. Or it works something like a garage door opener circuit anyway some type of internal switching.

So I could find the supply line splice into it for the keyed on power signal to disengage the front differential couple both wires to a hot side of a switch and take the switch leg back to the transfer case.

It would then operate normally shift to 4x4 still get the lighted engaged indicator on the shift trim AND if I want to go 4lo and not engage the front differential I could open the switch killing power to the transfer case leg but still powering the retract function.

What say ya'll. Do you think that would work?

I saw where some people had intermittent operation splicing into the brown wire for retract function. Think there is too much current draw to disengage or engage the servo that tying into the same line sends some weird voltage drop or race scenario of the switching mechanisms???

Might could still do the interrupt switch but do a different power source for retract?????

 

[THEFERMANATOR]

To keep the front axle from locking, you could put a toggle switch inline with the power output from the transfer case mounted switch. It has 3 wires to it, 1 is a keyed on power source, another is to lock the front axle(powered anytime it is in 4 wheel drive), and the last one is to tell the ECM when you are in 4 low. If you interrupt the one to lock the front axle, it would keep it from locking. You just have to make sure the front axle actuator has a keyed on power source to the brown wire you have to add in. Many have just hooked it to the wire that commands 4X4 which will engage it, but without power it can never dis-engage. There is a seperate switch in the front axle to turn the 4X4 indicator on. The new style electric actuator has internal limit switches that turn it off when it extends or retracts.

 

[schiker]

Ok it does appear more complicated than my previous post but maybe still work like I think depending.....

To keep the front axle from locking, you could put a toggle switch inline with the power output from the transfer case mounted switch. It has 3 wires to it, 1 is a keyed on power source, [1st wire is brown keyed on power which is recommended as power source to new servo motor right ] { put switch here new harness wire to hot side switched side to continue to transfer case}


another is to lock the front axle(powered anytime it is in 4 wheel drive), [ LT blue wire to actuator AND thru front axle switch if it engages to Electronic brake control BUT there are a couple of nodes and paths ...... ] and the last one is to tell the ECM when you are in 4 low. [ 3rd wire Gry/Blk appears to ground the ECM if the transfer case is in 4wd] If you interrupt the one to lock the front axle, it would keep it from locking. You just have to make sure the front axle actuator has a keyed on power source to the brown wire you have to add in. Many have just hooked it to the wire that commands 4X4 which will engage it, but without power it can never dis-engage. There is a seperate switch in the front axle to turn the 4X4 indicator on. The new style electric actuator has internal limit switches that turn it off when it extends or retracts.

The wiring diagram is a bit confusing with notes for models with K only and maybe for Auto transmission only plus gas vs diesel etc.

Alas its getting pretty complicated there are several nodes after the transfer case switch that the lt blue wire powers some depend on the axle actually engaging But see you are right and think it would be safest to break the lt blue wire front actuator wire right before the actuator if I wanted to make a 4lo 2 wd option with the servo mechanism.

 

[THEFERMANATOR]

Put your switch inline with the light blue wire anywhere between the transfer case switch and the actuator. The splice in it supplies power to the switch that turns the light on for when it is in 4X4.

 

[Big T]

Don't over think this. Here's a link to a photo of where I spliced the brown wire to a brown wire below a plug on the firewall behind the fuel filter manager:

http://www.thetruckstop.us/forum/album.php?albumid=530&attachmentid=40815

Ignore the GM instructions, as I had nothing but problems. I traced this brown wire back to the transfer case. Worked great and the job takes about 15 minutes max. I had purchased the cable pull actuator, but ended up selling it. The electric actuators are good. The thermo ones suck.

 

[Diesel Nut]

I have the 4x4 posi loc, both the cable driven which is nice, but also have the pin set up where the front end is locked in all the time. I have the pin set up in my 94 chevy 3500 which I plow with, works great. I also drive this truck in the summer time and have not seen any unusual tire wear or problems in my front end. The cable also works nice because you have the option of 2H, 4H, 2L, 4L. Which 2L is nice on a boat ramp when you need the extra torque to pull a heavy boat out, but dont want the wheel hoop when turning. The pin set up from 4x4 posi loc is about 80 dollars and takes about .5 hrs. The cable set up from 4x4 posi loc takes about 2 hrs the first time.

 

[schiker]

Missed the bullet this time. I did not seat the electrical plug into the transfercase switch past the little catch and it must have vibrated loose. Found it easy enough plugged it in fully and have 4x4 again.

When I do the servo update I might try the 2LO electrical mod then or go with Posi-lok but not going to try and fix something that isn't broken for now.

 

[Big T]

On Sunday I installed the electrical actuator from the wrecked '95 into my son's '94. Never could find the plug with the brown wire at the firewall, so I tapped into it at the transfer case switch.

When first installed, we could hear the actuator working, but it was not engaging 4wd. Pulled the actuator and observed it working, then remembered that there was a spacer that goes in before the actuator is installed. Fished the spacer out of the '95 with a magnet. Reinstalled and all was good on the '94. Now there isn't the 5 to 10 second delay that we were seeing with the thermo actuator, it's pretty instant.

 

[dag]

i got a 96 burb. i have the updated wiring for the electric switch. the brown is ran to a key on power source, then there's the other 2 wires that run to a 2 pin connector. if i can recall correctly, the 2 pin connector is suppose to have a mating connector. but i believe someone messed with this burb before i got it cause that mating connector is missing and there is no 4wd relay on the firewall. my question is, does anyone know what color wire and where it can be located in order to run a new command wire from the push button switch to the front actuator in order for it to engage? the ground is easy i can ground that anywhere.

 

[Big T]

i got a 96 burb. i have the updated wiring for the electric switch. the brown is ran to a key on power source, then there's the other 2 wires that run to a 2 pin connector. if i can recall correctly, the 2 pin connector is suppose to have a mating connector. but i believe someone messed with this burb before i got it cause that mating connector is missing and there is no 4wd relay on the firewall. my question is, does anyone know what color wire and where it can be located in order to run a new command wire from the push button switch to the front actuator in order for it to engage? the ground is easy i can ground that anywhere.

I spliced it to a keyed on wire in the harness behind the fuel filter manager. There’s a plug there with like 4 to 6 wires and I spliced in before the plug.

My ‘99 is up at our place in Montana and I’m down in SoCal working, so I don’t have it readily available to inspect.

 

[dag]

I spliced it to a keyed on wire in the harness behind the fuel filter manager. There’s a plug there with like 4 to 6 wires and I spliced in before the plug.

My ‘99 is up at our place in Montana and I’m down in SoCal working, so I don’t have it readily available to inspect.

yea i have the 12v on BRN spliced in but theres no 2 pin plug to connect to the new wire harness for the electrical actuator. does that plug get power or command from the Tcase switch?

 

[Big T]

yea i have the 12v on BRN spliced in but theres no 2 pin plug to connect to the new wire harness for the electrical actuator. does that plug get power or command from the Tcase switch?

IIRC that plug is before (just behind the differential axle) the plug to the actuator. The plug itself slides into a fitting behind the axle.