same here..i know its not broke i use it all the time lol..cant turn it at all..did they change the transfer case at all through the years?

 

The times i've ever had trouble with the encoder system there wasn't a code. Only transfer case related.

If you have the stubby "little round tube" with electrical wires running to it hanging off the passenger side of your front differential, you should ALWAYS be able to turn the front driveshaft by hand in 2wd.

When the encoder slides the locking collar/sleeve away from the carrier, it unlocks the stub shaft from the passenger side spider gear in the differential carrier. Meaning, the pinion and carrier/ring gear are no longer locked to the CVs. The spider gears always turn since they are connected to the driver's side CV, but the pinion and carrier, and hence, the front driveshaft (not the CV/half shafts!) shouldn't be locked in so you can turn them by hand in 2wd.

Not all 99-02 can be true live axle, my 01 yukon XL had the encoder and the front driveshaft would freewheel in 2wd. AFAIK, GM used the encoder system on EVERY IFS half ton since it went into production in the late 80s and should work like i've stated. If the 99s are truly different, or if ANY non-AWD (or full time 4WD) IFS 1/2 ton truck or SUV uses a true live axle, i would love to know this information.

 

idk, but i have the tube on the front diff and the encoder motor on the tcase because i replaced it last year..there is no way in hell i can turn my driveshaft by hand..it spins all of the time because it used to rub on my headers when i first put them on, and it annoyed me for 3 weeks until it cleared itself...

 

I'm thinking the t-case is not disengaging the front prop, then. I had mine on a lift and did a driveline slop test and the rear axle makes the front prop shaft spin. The front tires, however, do not engage the front prop shaft.

Of course it could be something similar to the Rover t-case where the front viscous coupling gets fried, but I don't think our NP t-cases get such fancy equipment.

 

There is a clutch pack in the transfer case that keeps some friction against the front output shaft. The only reason that front propeller shaft should spin freely, is if that clutch pack is smoked. Clutch pack is similar to what you see inside an automatic transmission.

I'll say it again, everything that the OP described in his original post is normal for that model.

 

I'm not going to argue. There's some piece of information missing. The early autotracs might work different, i don't know... that's why i am asking if and how they are different. I for sure know how my 05 works. There are multiple posts on the forums documenting the 07+ autotrac trucks having freewheeling front driveshafts in 2wd also.

I just went outside, again, and turned the front driveshaft of my 05 yukon and it turns easily. We just had a big storm go over two hours ago so i went and tried the auto4wd, 4hi, and 4lo in the back yard and all worked fine (all four tires were digging in the grass when i punched the gas.... stabilitrak was turned off to keep the computer from killing power when the wheels started spinning). After spraying the truck off and rolling back into the garage, the front shaft still turns by hand. It has worked this way for the 6 years and 112k miles i've had the truck and used the 4wd hundreds of times. The clutch pack isn't smoked.

Let's figure this out for future reference. I'll concede that maybe the 99-02 (or thereabouts) autotracs are different. I remember my front shaft spinning freely on my 01 XL, but i could be mistaken.

 

You really don't like to be wrong, do you..... lol. Have a nice night Sintered.

 

I don't know if it helps anything but I can turn mine by hand easy when its in 2wd..


I had some encoder motor issues too mine would shift like it was in 4lo but it would be in high so by time you reached 20mph it was in o/d trying to lock the converter and would bog down and almost go dead.. New encoder fixed that right up..

 

Shut up Bumpers!!

 

The Stabilitrak T-case is different from your normal NP243 in that it has a hydraulic/viscous clutch for the forward output shaft. I had an 05 Suburban with Stabilitrak 4x4 that could unlock the front prop. Of course, it would also go stupid and lock up brakes when I hit the gas, must've had something to do with not being calibrated for 4' extra wheelbase.