weird 4x4 problem 2003 Chevy Tahoe Z71

[density]

Hi!
I have something weird going on in my 2003 Chevy Tahoe Z71. The all wheel drive works better than the 4 wheel drive. If I get it stuck in 2H: (1) I switch to 4H and I am still stuck; (2) I switch to 4L and I am still stuck; (3) I switch into auto 4wd and I roll out like I am on dry ground. How can this be?


Not to long ago I changed the encoder motor because the old one died. After finding the current problem I changed the front actuator motor and the front diff oil looked terrible (including shavings on the plug) so I also put new oil in there.


When its jacked up and I let it idle in 4 hi, 3 wheels spin at the same rate with the front left spinning weakly. But on the ground the front wheels don't spin in 4hi but they do spin in auto4wd ? I don't know what to think here.



Any guidance will be much appreciated. Thanks in advance.

[j cAT]

I find the vehicle 4wd confusing to me with your post.

your vehicle should have auto 4wd . this is activated when the vehicle PCM see a slippage.

with 4wd lo/hi you are in locked 4wd. the front axle and rear are locked as one.

when stopped and stuck you use 4wd hi/lo not auto.

when operating on slippery wet/snow roads you use auto 4wd.

with the front diff damage you may need replacement. with the encoder motor failure if that was from tranfer case fluid not replaced that could also be another repair.

the drive train fluids require replacing every 40,000miles if not used all that much . if your using it all the time hauling on dirt roads/plowing then this should be replaced every year. front/rear diff, transmission,rear diff....

operating on dry solid pavement will chew up the gears.

[density]

Originally Posted by j cAT

I find the vehicle 4wd confusing to me with your post.

your vehicle should have auto 4wd . this is activated when the vehicle PCM see a slippage.

with 4wd lo/hi you are in locked 4wd. the front axle and rear are locked as one.

when stopped and stuck you use 4wd hi/lo not auto.

I get it stuck on purpose to test the 4wd. as stated above, in 4HI the front wheels dont spin when on the ground and hence I get no traction to get out BUT when in auto 4wd the front wheels do spin and I get decent traction. I am aware that this does not make sense and that is why I am posting this question here.

Thank you for explaining to me when to use auto 4wd and 4hi and when to change the oil.

[j cAT]

Originally Posted by density

I get it stuck on purpose to test the 4wd. as stated above, in 4HI the front wheels dont spin when on the ground and hence I get no traction to get out BUT when in auto 4wd the front wheels do spin and I get decent traction. I am aware that this does not make sense and that is why I am posting this question here.

Thank you for explaining to me when to use auto 4wd and 4hi and when to change the oil.

if the 4wd does not lock in the front to rear axles then this is the encoder sticking/binding. old fluid can do this or using the wrong fluid. the tracII fluid is available at the dealer ship only last time I checked. the transfer case fluid is blue. if it is gray or worse black then change it and perhaps it will work . if not then I would expect the 4wd service light to be on if so get the GM drive train failure code and post here for some guidance.

[density]

Well it is locking. Or is it? When on the lift up in the air running in 4HI, 3 wheels spin with the front driver side spinning weakly enough to stop by hand. But on the ground the front wheels are not spinning. So maybe the center diff is unlocking under force?

I get no codes. when the encoder motor went I had c0303 and c0374. now there is no light, no code. so i cant rely on the computer to tell me what to do to fix this no traction issue.

When I looked at the fluid it didn't look awful but I will change it now just because I don't have a better idea.

[j cAT]

Originally Posted by density

Well it is locking. Or is it? When on the lift up in the air running in 4HI, 3 wheels spin with the front driver side spinning weakly enough to stop by hand. But on the ground the front wheels are not spinning. So maybe the center diff is unlocking under force?

I get no codes. when the encoder motor went I had c0303 and c0374. now there is no light, no code. so i cant rely on the computer to tell me what to do to fix this no traction issue.

When I looked at the fluid it didn't look awful but I will change it now just because I don't have a better idea.

with what your saying my guess is the encoder is working and the electrical sensors for the 4 wd are happy. the reason it is not working [traction on the front axle] is because the transfer case is in need of re-building.

normally this would be black transfer case fluid and bits of metallic material with the case drain .

you may need a front diff and a transfercase repair.

do you operate this in 4wd on solid pavement ?

[density]

use 4HI on pavement? hell no man. I changed the t-case oil and the old oil was pretty well cooked, almost black. but there was no metal on the plug. put the new oil and no luck. so ill probably have to open up the t-case and adjust something. Maybe something in there got out of whack when I changed the encoder motor? My first thought was that the t-case was blown but then how is it working for the AUTO 4WD ?

[density]

changed the fluid and no change. so tomorrow I am going to have to take the t-case apart and see whats going on in there. hopefully it just needs a little love and not a lot of money.

[j cAT]

Originally Posted by density

changed the fluid and no change. so tomorrow I am going to have to take the t-case apart and see whats going on in there. hopefully it just needs a little love and not a lot of money.

black fluid means 90% trashed.

[j cAT]

Originally Posted by density

use 4HI on pavement? hell no man. I changed the t-case oil and the old oil was pretty well cooked, almost black. but there was no metal on the plug. put the new oil and no luck. so ill probably have to open up the t-case and adjust something. Maybe something in there got out of whack when I changed the encoder motor? My first thought was that the t-case was blown but then how is it working for the AUTO 4WD ?

there are wear items in the transfer case, the black is the material that creates the friction for the axle connection front to rear. with that worn down you get this.

no codes will throw when the transfer case is worn out. these codes report the encoder/locking actuator / wiring operation.

operating in any 4wd position including auto 4wd will rapidly wear out the transfer case/ front diff. on solid dry pavement .

[density]

makes sense. but how is it that the auto4wd works if the t-case is trashed?

[777stickman]

Very strange indeed!! Check for 12v at front actuator in 4HI, 4LO & Auto.

[density]

it looks good so im pretty sure its getting 12v. when it is jacked up the front wheel spins so im pretty sure the actuator is doing its job.

at this point I am trying to figure out weather to open the transfer case or the front diff ?? its got to the seals and gears in either one of these places. I am leaning to the t-case (even though its like an effin 8 hour job) because if the carrier in the front were broken i don't think auto4wd would work.

Front diff or t-case? any thoughts?

[777stickman]

Originally Posted by density

it looks good so im pretty sure its getting 12v. when it is jacked up the front wheel spins so im pretty sure the actuator is doing its job.

Pretty Sure? Well, I'm pretty sure you're going to need some luck with this, so I'll start that ball rolling by saying--------------Good Luck to You.

[density]

above i already said i changed the actuator. so the chance that this is not working is slim. thanks for wishing me luck. Do you have any kind of mechanical advice?