PDA

View Full Version : 96 GM Pickup 4WD Problems



Alfons
11-29-2009, 06:04 PM
I have a stock 96 GM K1500 that stopped operating in 4wd. The transfer case works - both drive shafts work with 4 Hi selected, rear wheels turn but not the front (I have the truck lifted). I see that the 4wd light doesn't come on when the t-case is selected to run both drive shafts, so I thought it might be something electrical, unfortunately all I have is a Haynes manual that makes no reference to the front axle, electrically or mechanically (another good book for the outhouse).

I see a unit of some type (looks like a large solenoid/actuator) that's attached to the front diff and has wires going to it - can anyone tell me what this is? Does the front axle need a coupling actuator similar to a YJ vacuum motor?

Does anyone have full wiring diagram for this model truck?

Some info would be greatly appreciated.

mud bros.1
11-29-2009, 06:10 PM
its the exact same junk the yj has

posi lock makes a cable for that too here is a link so you can make your own:beerchug:
http://www.4x4posi-lok.com/app_chevy-k.html

Alfons
11-29-2009, 07:06 PM
Thanks Andy, I'll have a look at that whole assembly tomorrow & see what's failed. I did a bit of research this evening & see a part called a part called a "thermal actuator" that's connected to the electrical harness - any idea how this works?

markr1001
11-29-2009, 07:13 PM
it heats up and when its warm it pops out and engauges, if you get them too cold they have a tendency to disengauge and its usually at the worst time like a water crossing with ice cold water, they are junk, you can swap out one from i think it is 99 and up as they are just electric and stay in when its suposed too. but i think it requires a wireing pigtail or something, my dads truck has the same one and its definatly not a great setup

markr1001
11-29-2009, 07:18 PM
i just did a quick search on dormanproducts.com and both the upgraded actuator and wireharness are listed there, i know ctc and partsource can get dorman parts as well as i know napa can cross reference there numbers

Alfons
11-29-2009, 07:24 PM
it heats up and when its warm it pops out and engauges, if you get them too cold they have a tendency to disengauge and its usually at the worst time like a water crossing with ice cold water, they are junk, you can swap out one from i think it is 99 and up as they are just electric and stay in when its suposed too. but i think it requires a wireing pigtail or something, my dads truck has the same one and its definatly not a great setup

Thanks, I thought that's what I was reading, but couldn't believe that for a simple function, anyone would be dumb enough to design an actuator that could decide on it's own when it wanted to disengage. The YJ vacuum motor approach was thought out better than this.

Alfons
11-29-2009, 07:26 PM
i just did a quick search on dormanproducts.com and both the upgraded actuator and wireharness are listed there, i know ctc and partsource can get dorman parts as well as i know napa can cross reference there numbers
Thanks, I'll have a look at that tomorrow.

mud bros.1
11-29-2009, 08:09 PM
same thermal idea and set up as the crapy ford auto locing hubs.

avoid the stock setup like the plague

Alfons
12-06-2009, 05:11 PM
I decided to use the new style electric actuator - it's fairly easy to install, but I had some problems with the electrics so it took me somewhat longer than I figured. Dorman has all the components that theoretically work together to replace the original thermal actuator - here's what's needed to make the "upgrade" and some comments of where I found my problems:


Electric 4x4 actuator - Dorman PN 600-101: This unit has three wires - one for power, one for ground, and one to actuate the forward motor rotation. Also, this unit's internal part is about an inch shorter than the thermal unit & requites a "plug" of that length to be shoved into the hole to make up the length difference and allow it to engage the axle.
Wiring Harness - Dorman PN 600-600: This harness package includes the steel plug (it's about 1" round by 1" long - it needs to be large enough in diameter so it won't slop around & long enough to make up the difference in length between the two actuators & the ends need to be rounded so the plug won't catch on anything in it's back & forth travel). The wiring harness actually isn't much - it has two plugs on it and a bit of wire. The plug for the new actuator is actually useful, the other plug was a different style & I needed to cut off the one from the old actuator to replace that. The one long wire on this harness is supposed to splice into the circuit that supplies the power to the t-case switch & this is where I ran into my problems.

The installation instructions come with the wiring harness package - nothing is included with the actuator even though it's listed as an upgrade for the 96 K1500. These instructions include a number of schematics that tell you where you to make the splice - I couldn't get to that part of the harness as it was sitting on top of my transmission instead of on the side where they indicated it should be. I figured that as long as I got the splice somewhere along the power feed wire, I should be OK & so I made the splice hear the t-case switch - initially, it all looked good, I had 12 volts on the power line & 12 volts on the trigger line. The problem was, I needed to use a ground external to the circuit to read the 12 volts on the power line, but using the only circuit ground that was available, I had no 12 volts for the power - this told me that either the wire I splice to or the wire for the common ground weren't in the same circuit. After screwing around for a lot longer than I should have, I finally decided that all my short cuts were a waste of time (a couple of cold days on my back under the truck searching for wires seems to give me a reality check), so I made myself a new harness that uses 2 relays to create the two 12 volt inputs needed with a common ground - this all works great - I should have done this when I couldn't get to the connector Dorman specified. If anyone needs to do something similar, all they need to buy is the Dorman actuator & get a connector for it from a dealership & the rest is easy to fabricate. I'll be glad to post the sketches for the schematics of my harness & a few simple instructions for anyone interested.

markr1001
12-06-2009, 06:36 PM
awesome! i would love to see it, as i might be doing this in the winter to dads truck, also if you dont mind me asking, about how much did it cost?

Alfons
12-06-2009, 08:03 PM
awesome! i would love to see it, as i might be doing this in the winter to dads truck, also if you dont mind me asking, about how much did it cost?

I'll make up a sketch over the next couple of days & post it. The parts I got were discounted, otherwise, I would have reconsidered my approach if I had to pay full retail prices. My alternative options would have been using a Posi-Lok as suggested by Andy (close to the price I put out for all my parts) or getting a used actuator & connector from junk yard. I'll need to look at my invoice, but I believe the retail cost of the actuator was over $200 and the harness was listed close to that. I'll post a material cost to the parts of the harness I made - dirt cheap compared to the dorman harness.

If you have the time, you might want to check the dealership price for that 1 connector for a 99 K1500 4x4 Actuator or you might check at an auto salvage yard for both the actuator and connector - that'll give you the majority of the setup pretty cheap. The actuator is pretty easy to check out, connect the black to the negative side of a battery & the other 2 wires together to the positive & the motor will wind the activator to full length. Remove the trigger voltage (light blue in my case) and the motor will reverse and wind it back in. It's a simple unit, and will stay in either position with power removed, so you can "lock" the split shaft and leave it there if that suits you (not as easy to lock the shaft as it is on the YJ D30).

Alfons
12-08-2009, 11:53 AM
Here's what I did. If you need any details or additional explanations,let me know.

This is a picture of the schematic that I made my harness from:

http://www.jeepkings.ca/forums/images/imported/2009/12/69.jpg

This is my sketch of where the actuator sits, the new harness plugged in, and the attachment to the old harness - please take note of my comments on the sketch:

http://www.jeepkings.ca/forums/images/imported/2009/12/70.jpg

With reference to the schematic, here's a picture of the fuse panel in the truck showing the Add-a-Circuit that I used to power the electromagnet for Relay 1 (Pin 85 or 86 - one is for power and the other for ground, doesn't matter which way you attach them). This spot I used was for the 4WD circuit with a 25 amp circuit - this power was needed to heat up the gas in the thermal actuator. Since I don't need that anymore, I used an overkill of 10 amps for the relay (could probably get away with 2 amps or less) and 15 amps for the rest of the old circuit (not much of it left, could use 10 amps or less easily)

http://www.jeepkings.ca/forums/images/imported/2009/12/71.jpg

Here's the ground connection for Relay 1 - what you're looking at is a tube that goes under the steering column (the plastic cover is removed from the bottom of the dash) - sorry the pic is poor quality, but the rust should make up for it:

http://www.jeepkings.ca/forums/images/imported/2009/12/72.jpg

This picture shows where I mounted the relays:

http://www.jeepkings.ca/forums/images/imported/2009/12/73.jpg

These next two pictures show the fused output power connections for both relays. Relay 1 output doesn't need much, this is the power for the trigger to switch the actuator motor to extend & when it's shut off, it retracts (as long as Relay 2 output is live) - I used a 10 amp fuse. For Relay 2, I used a 15amp fuse - again you can get away with less. This power is to drive the actuator motor & the way I've got it attached, that line is hot as long as the key is in run - it's off when the key is off:

http://www.jeepkings.ca/forums/images/imported/2009/12/74.jpg

http://www.jeepkings.ca/forums/images/imported/2009/12/75.jpg

This picture just shows where I hooked up the output power ground - this ground wire goes from the black wire on the C2 connector to this point:

http://www.jeepkings.ca/forums/images/imported/2009/12/76.jpg

To measure the wire lengths you'll need, use a piece of household electrical wire and bend it to shape along where you want to route the whole harness - this gives you a dry-run for the fitment & you end up with the whole thing fitting like you knew what you were doing :beerchug:

Alfons
12-08-2009, 12:02 PM
I guess the IMG tags don't work here anymore, here are the pictures in the order I talked about them

My sketches:

Alfons
12-08-2009, 12:05 PM
Fuse Panel & Under Dash GND connection:

Alfons
12-08-2009, 12:07 PM
Relays & Output Power Connection:

Alfons
12-08-2009, 12:08 PM
Output Power GND to Actuator:

markr1001
12-08-2009, 10:06 PM
Awesome!! gonna copy it all down and save it to reference later