is my 4wd supposed to work like this?

[jsomething]

i have an 04 envoy xuv with an l6 and do not have a g80

I recently went through my 4wd system a-z checking everything because of a problem i had with the actuator not fully engaging the disconnect.
when i was done i was confident that my 4wd was working properly
up on jackstands in 4lo if i rotated one of the front tires the other would turn in the opposite direction.
if i started it up and put it in drive i would get 2 turning (one in front, one in rear)
and if i held the tires that were turning to stop them, the opposite tires would start turning.
so i thought everything was good

however last week i got stuck in some mud and only one tire would turn (drivers side rear)
didnt seem to matter what setting it was in the front tires wouldnt turn.

if i didnt just go through the whole system i would think something was wrong.
so im thinking maybe thats how its supposed to work? maybe something about giving all the power to the wheel thats slipping..
probably has something to do with highway speeds and turning and what not.
if thats the case i need to fix it.

i figure putting in a no-slip in the rear would give me two wheel drive
but is there anything i can do to help the front tires engage?
Id really like to start delving into the offroading world with this truck soon but not if its like this.
thanks in advance.

 

[The_Roadie]

Welcome!

Front axle disconnects often wear and then they work only erratically. You might consider taking it apart and regreasing it. We have a tech article on offroadtb.com

There are few limited slip options for the rear. The factory option was a G80 automatic full locker that engages when either rear wheel slips, but you can swap in a junkyard axle with a G80 for less $$ than buying a new G80 and installing it. .

Were you in 4HI for your mud run? The fronts should have had SOME action in that case, unless you've been ignoring the vitally critical 50K fluid change interval on the transfer case. What's its history?

 

[Robbabob]

Welcome to the Nation!

The Roadie will be along shortly, he is God when it comes to this.

Edit: he's already in the house! LOL

 

[jsomething]

Front axle disconnects often wear and then they work only erratically. You might consider taking it apart and regreasing it. We have a tech article on offroadtb.com

yea I did this when i was troubleshooting the system, looked surprisingly good actually. also followed your guide for cleaning up the actuator.


There are few limited slip options for the rear. The factory option was a G80 automatic full locker that engages when either rear wheel slips, but you can swap in a junkyard axle with a G80 for less $$ than buying a new G80 and installing it. .

Were you in 4HI for your mud run? The fronts should have had SOME action in that case, unless you've been ignoring the vitally critical 50K fluid change interval on the transfer case. What's its history?

was in 4lo when i got stuck and the majoriry of trying to get out. did try 4hi at some point to see if it made a difference, but nothing
and i guess i have been ignoring the fluid change, dont know the history, have only had the truck about 6 months. but have not changed the fluid in the transfer case.

cool, well thanks for giving me a couple avenues to pursue.
im glad its not supposed to be like that. although now i have to find another problem.

 

[jsomething]

As a followup are you suggesting the g80 axle from a junkyard is a better option then one of those no-slip things that replace the gears in the open axle?

Also if my fluid wasnt changed would that alone be the problem or would that just cause more wear and i probably have something damaged in the transfer case?

 

[Bill05EnvoySLT]

My .02 Cents... If you had ZERO traction in the front axle (No drive in the front) either the front disconnect didnt engage or issue with transfer case. I would suspect starting with the disconnect first, may have broken the fork, the tires will spin just from momentum of the shaft engaging from the transfer case and would imagen it pretty simple to stop the tires manually by hand, that being said the other wheel would then take up the traction. this is the function of the carrier, however if the motor to engage the front disconnect did not engage there would be no FORCE (Torque) to the front wheels and just be moving on drive shaft motion continued to the carrier. This seems based on your information to be the best senario. Def want to investigate the disconnect first. you have to pull passenger side axle out and unbolt disconnect from oil pan and inspect.

Again I may be off but its where I would start..
Oh yea change the Transfer case fluid. 2 quarts AutoTrak II dealer item. and get a good pump to put it back in the fill hole is not user friendly.
Fill hole plugs take 10MM HEX to open. crack the top fill plug first then make sure you can remove the bottom one second. Its been known to happen (taking out the drain plug first to find the fill plug is seized up.

 

[jsomething]

Thanks bill.
I did recently disassemble and regrease the disconnect. It was in near perfect condition about a month ago. Didnt even have worn bearing races. so i dont think thats the problem.
Thanks for the tip on the fill plug. I had that exact problem with the front differential. Ended up having to weld a socket onto it as a last resort. Man was that a pain. Nice to know ill probably have the same problem on the transfer case..

 

[Bill05EnvoySLT]

No indicator lights on? No flashing of the 4X4 switch? with the truck on but not running switch to 4-hi and listen for encoder and transfer motors to engage.. do you hear seperate clicking from both front and transfer case? does it indicate engaged?

I think I remember The_Roadie stating he once destroyed the front carrier but did not immediately notice it... I could be wrong. maybe the ring gear is shaved down and its just not engaging. I would think this would sound pretty horrible if this was the case? no forgein noise?

 

[The_Roadie]

As a followup are you suggesting the g80 axle from a junkyard is a better option then one of those no-slip things that replace the gears in the open axle?

Also if my fluid wasnt changed would that alone be the problem or would that just cause more wear and i probably have something damaged in the transfer case?

You can spend $500-600 on a limited slip to put in your existing 8.6" rear end. Not too many folks selling used limited slip units. Check Randy's Ring & Pinion site for alternatives. I see four listed there now. Installing them and reshimming the gear set is going to run you another $250-300 at a driveline shop.

The G80 is a fantastic product, being a full mechanical locker. By careful feathering the throttle to avoid full-torque, high-speed engagement that tends to break them, I do a LOT of two-wheel-on-the-rocks kind of offroading. This is one my old videos from early on in my career that shows how it works. Without the G80, this hill is unclimbable.

https://www.youtube.com/watch?v=24SwmSN0-bI

I broke my 8.0" diff once in Montrose CO (an epic thread ensued), and got a replacement 8.6 with G80 (and stronger axles) that has gotten me through some world class trails like the Rubicon for the last five+ years. All for only $400.

If low or old fluid has damaged the clutch plates in your transfer case, then no torque is going to be sent forward, no matter how good your actuator is. Another $400 trip to the junkyard would be the cheapest way out of that mess. Hard to understand why you'd go to the trouble of the splined disconnect rebuilding and never check or refill the transfer case. Every 50K without fail. Check level more often than that if you're on trails where you couldn't get back to pavement in 2HI.

 

[The_Roadie]

I think I remember The_Roadie stating he once destroyed the front carrier but did not immediately notice it...

Not me. I destroyed a rear diff during an ill-advised deep snow extraction of a 2WD work van of an HVAC company who was in way over his head on a mountain trail that was absolutely impassable in the shadows. April 2009: Montrose, CO.

The epic rescue thread and how members came to get me in CO and back to San Diego was (IMHO) Trailvoy's finest hour:
http://forums.trailvoy.com/showthread.php?t=56225

 

[jsomething]

Yea no check lights
Switch does indicate engaged.
Havnt had a chance to scan for codes. I do hear both motors. No weird noises at all. And i filtered all the front differential fluid through a magnet screen thing and there was absolutely no metal shavings. When it was in the air everything seemed to work fine. Its seems maybe it works but i have no torque. How would i test this? Would putting it in the air and holding the brakes while hitting the gas be good enough? Or should i chain it to my other truck and dig holes in the backyard?

I do suspect something with the transfer case. But would ild fluid alone cause this or would something need to be damaged. Also i think i need to check out the motor on the transfer case. I didnt see any articles on rebuilding that. Or did i miss it?

 

[The_Roadie]

Low or old fluid could damage the clutches. Without clutches, no torque is sent out the front driveshaft. If you or anyone else driving the vehicle used the A4WD mode a lot, that could have worn out the clutches. It's a stupid mode to have on the NP226 TC. Also, A4WD mode carries the risk of breaking an internal bearing carrier mount. Then the TC is toast. GM beefed it up somewhere around 2005.

If the encoder motor was failing to move to its commanded position, you'd get a flashing light indication on the mode control switch. Most folks just buy a new encoder motor, but a few have disassembled them and found problems in a planetary reduction gear set or the permanent magnets mounted around the armature. Very rare to get pictures, and the site isn't very searchable at the moment. If you've ever taken apart a permanent magnet motor it will be very familiar to you inside there. No rivets need to be drilled to get inside, at least.

That said, we HAVE had a few instances on offroadtb.com recently of the system seems to be working OK, no flashing lights, but functionally it's still in 2WD operation. Those ended up being a new failure mode of the encoder motor BRAKE function. When the TCCM commands the encoder motor to go to a position, it sets a brake solenoid to hold the motor from moving around (in 4HI and 4LO modes only). You can't tell this failure mode from a bad transfer case without using a high end scan tool or a GM Tech II or my troubleshooting the encoder motor on a bench.

 

[jsomething]

Thanks roadie
That video is perfect. Exactly what my trucks not doing heh
It even looks like your not losing all your front traction to the wheel thats in the air. I was under the assumption the front didnt have a locker. And i went through all that because im very mechanically enclined but brand new to 4x4. Kinda learning as i go. Figured with the front drive shaft turning i didnt have a problem in the transfer case. I will be attacking that next. And thanks for the advice and vid. That helped me decide the g80 is exactly suitable to what i want.

 

[The_Roadie]

You're one of the 2% of people seeing that video who understands the significance of the front wheel being in the air! It illustrates how the transfer case is not slipping, but a hard lock front-to-back. The rear G80 locks up early in the hill climb, Putting all torque to the wheel with traction. This slows down the rear driveshaft. Since the TC is a front-to-back locker, the front driveshaft also slows down to match the RPM of the rear. The front diff carrier is indeed open, so the front tire that's touching the ground isn't getting any traction, but the front tire in the air *is* leaking torque and spinning twice as fast as the one on the ground. The front tires aren't contributing to the hill climb, but the G80 is the enabling technology.

Another secret I wasn't using in this video, but all serious offroaders (including me nowadays) do is to air down. Reduce the tire pressure to 16-18 PSI. It DOUBLES your traction and allows things like this hill climb to proceed successfully with slow and deliberate progress.

Many offroaders spin all four tires with high throttle action, and they manage to get up trails using momentum partially stored in the spinning tires and that's another kind of hill climbing illustrated in this video. I quit doing this because it breaks stuff I need to get home.

https://www.youtube.com/watch?v=7OkERcoN0FY

Airing down on Utah slickrock (sandstone that acts like 10 grit sandpaper) is climbable at up to 40 degrees I discovered.

https://www.youtube.com/watch?v=k-lt3sLaktk

Another one where a map flies out the window.

https://www.youtube.com/watch?v=AheKwL2AYhE

A trail in Moab, Utah called "Fins'n'Things" very near the now-closed world-famous Lion's Back.



My Fins'n'Things run:

https://www.youtube.com/watch?v=WCnRaNqIKAk

 

[IllogicTC]

Not me. I destroyed a rear diff during an ill-advised deep snow extraction of a 2WD work van of an HVAC company who was in way over his head on a mountain trail that was absolutely impassable in the shadows. April 2009: Montrose, CO.

The epic rescue thread and how members came to get me in CO and back to San Diego was (IMHO) Trailvoy's finest hour:
http://forums.trailvoy.com/showthread.php?t=56225

It's funny that today marks the 5-year anniversary of that. You can see how it reached a beautiful pinnacle at that point, and then slid down a slope of ad diarrhea.

 

[jsomething]

Thanks for the help roadie. Videos were interesting.
Followed them to your youtube Chanel to check out the rest.
I got some building to do. And a lot of learning.
Sucks about lions back. That particular obstacle was on my bucket list.
Noticed you haven't uploaded any vide in a while.
Are you not offroading anymore?

 

[The_Roadie]

Are you not offroading anymore?

Actually, I've done a LOT more offroading, but haven't had the time to:

a) Edit down the videos

and more importantly

b) Start a new Youtube account with a better name than the now-hateful "trailvoy". I'm severely embarrassed by that nowadays. I have a plan, but this site and offroading keeps getting inthe way. Check out the trip reports in my signature for more updated picture threads anyway.