4wd Problem Shifts But Won't Engage.

adbaker · December 12, 2009

2004 Silverado ext Z71 5.3l autotrac 4wd

Hey Everyone! Hope you can help me out. My front axles won't engage. This is what i've done/noticed so far...

1. I have no "service 4wd" on the dic

2. My dash switch is working. I can here the transfer case switching between 4hi, 4low, auto and 2wd. When in 4lo its definitely geared down, but still nothing up front

3. When in 4hi my front driveshaft is locked, but the axles/tires/diff are not.

4. Unhooked the wiring harness from the differential actuator. Brown wire has power, nothing else. Is the blue a signal wire or should it have power all the time when i'm in 4hi (thought i'd read that somewhere?

So does this mean my actuator is cooked. I haven't pulled it yet, ran out of time tonight, but i'll be back at it in the morning. I just wanted to see if the voltage reading of the brown only was proper.

If anyone can confirm or give me some other troubleshooting tips, i'd appreciate it.

Thanks

Adam

Nytemare · December 21, 2009

I'll see if i can grab one. Thanks again. Just out of curiosit, should i be able to lock the axles manually? I tried pushing into the actuator hole with the blunt end of a ratchet. I could move something about 1/4 inch and it would bounce right back. Didn't want to push too hard though.

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Yeah you were pushing on part 17...thats the plunger that the actuator pushes to engage the passenger axle.

If you push it while spinning the passenger tire slowly it should engage and start spinning the drivers side too. It should move more than 1/4", but the front end has to be moving for it to slip in.

Not the actuator! Threw one in to see. Guess its a problem somewhere in the shift tube. I'll have a look and update when i get a chance.

BTW Nytemare, i'm pretty sure you're exploded view isn't quite right for my truck. It looks like the old thermal actuator hook-up. Things are similar but if you have one for the '04 with autotrac, you might want to edit your post for future reference.

Thanks again for the help, i'll fill ya in later.

Ad

No man...that's a front diff explode right out of a service manual for 02+ The parts may not look exactly the same on yours...But its generally the same.

The thermal actuator is a totally different diff all together.

Pull the passanger side off and see if there's a broken part in there. If not...I'm sorry to say...you may have a nuked carrier (spider gears).

adbaker · December 12, 2009

It does look like its spring returned so I would say...that one wire is the signal...the other is the ground. The 12V signal shifts the pin when you shift to 4wd...and the signal should go away when you shift to 2wd, and the pin gets shuffled to the unlock position by the spring.

So i pulled the actuator. It moves properly but i don't know if it moves enough. It extends about 3/4 of an inch. It looks like it can only extend another 1/8 to a 1/4 of an inch because of some plastic stops. Anyone know if this is enough movement. If its moving properly then my probs in the diff (no thanks). Here's a few pics of the distance it moves...

Nytemare · December 12, 2009

That's about right man.

You may have to go inside and see if part number 15 is damaged.

adbaker · December 12, 2009

Thanks...i should've said "only reply if i don't have to break open the diff"

Crap

adbaker · December 12, 2009

Thanks for all the help nytemare. I'll post again when i get a chance to open up the diff.

Ad

Nytemare · December 12, 2009

Thanks...i should've said "only reply if i don't have to break open the diff"

Crap

LOL....you don't have to brake open the diff. you just have to pull the passenger side shaft off and the housing there....your not actually going into the diff its self.

I would however give another actuator a try...that one may be working when taken out and no load...but when pushing on the plunger it may not have enough power.

adbaker · December 12, 2009

Thanks...i should've said "only reply if i don't have to break open the diff"

Crap

LOL....you don't have to brake open the diff. you just have to pull the passenger side shaft off and the housing there....your not actually going into the diff its self.

Thats right...wallowing in self pity, wasn't thinking right. Thanks for the refresher.

Nytemare · December 12, 2009

Thanks...i should've said "only reply if i don't have to break open the diff"

Crap

LOL....you don't have to brake open the diff. you just have to pull the passenger side shaft off and the housing there....your not actually going into the diff its self.

Thats right...wallowing in self pity, wasn't thinking right. Thanks for the refresher.

Sorry I edited that while you were replying.

I would however give another actuator a try...that one may be working when taken out and no load...but when pushing on the plunger it may not have enough power.

adbaker · December 12, 2009

I'll see if i can grab one. Thanks again. Just out of curiosit, should i be able to lock the axles manually? I tried pushing into the actuator hole with the blunt end of a ratchet. I could move something about 1/4 inch and it would bounce right back. Didn't want to push too hard though.

Ad

Nytemare · December 12, 2009

IIRC...the front diff actuator moves...you could pull it out and see if the piston is moving, or if something is broken off.

Other than that I could post an exploded view of your front diff if that will help you

Nytemare · December 12, 2009

I'll see if i can grab one. Thanks again. Just out of curiosit, should i be able to lock the axles manually? I tried pushing into the actuator hole with the blunt end of a ratchet. I could move something about 1/4 inch and it would bounce right back. Didn't want to push too hard though.

Ad

Yeah you were pushing on part 17...thats the plunger that the actuator pushes to engage the passenger axle.

If you push it while spinning the passenger tire slowly it should engage and start spinning the drivers side too. It should move more than 1/4", but the front end has to be moving for it to slip in.

adbaker · December 12, 2009

IIRC...the front diff actuator moves...you could pull it out and see if the piston is moving, or if something is broken off.

Other than that I could post an exploded view of your front diff if that will help you

You remember correctly!

I just haven't had a chance to pull it out yet, that'll be in the morning. I believe it should move about 1.5 inches. I guess i was wondering whether the voltage reading i got was correct, or whether there should be other hot wires.

Thanks for the reply

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Nytemare · December 12, 2009

IIRC...the front diff actuator moves...you could pull it out and see if the piston is moving, or if something is broken off.

Other than that I could post an exploded view of your front diff if that will help you

You remember correctly!

I just haven't had a chance to pull it out yet, that'll be in the morning. I believe it should move about 1.5 inches. I guess i was wondering whether the voltage reading i got was correct, or whether there should be other hot wires.

Thanks for the reply

Ad

I would think that one would be hot when in 4(hi or lo) and one hot when in 2wd. Basically one to pust the piston...and one to retract....ofcourse it could be spring returned.

I'll have to look at the exploded diagram

Here you go....looks like its spring returned.

adbaker · December 21, 2009

Pull the passanger side off and see if there's a broken part in there. If not...I'm sorry to say...you may have a nuked carrier (spider gears).

That'll be this week some time

Thanks again

Ad

adbaker · December 15, 2009

I'll see if i can grab one. Thanks again. Just out of curiosit, should i be able to lock the axles manually? I tried pushing into the actuator hole with the blunt end of a ratchet. I could move something about 1/4 inch and it would bounce right back. Didn't want to push too hard though.

Ad

Yeah you were pushing on part 17...thats the plunger that the actuator pushes to engage the passenger axle.

If you push it while spinning the passenger tire slowly it should engage and start spinning the drivers side too. It should move more than 1/4", but the front end has to be moving for it to slip in.

Not the actuator! Threw one in to see. Guess its a problem somewhere in the shift tube. I'll have a look and update when i get a chance.

BTW Nytemare, i'm pretty sure you're exploded view isn't quite right for my truck. It looks like the old thermal actuator hook-up. Things are similar but if you have one for the '04 with autotrac, you might want to edit your post for future reference.

Thanks again for the help, i'll fill ya in later.

Ad