(SOLVED) 4WD is gone but still have low range?

[Glasscaster]

The 4wd stopped working a while back. I ran through the flow chart for the 4wd. Passenger side front tire up in 4hi, tire spun freely, no driveshaft spin. Both front tires up in 4hi, passenger tire turns without turning the driver side or drive shaft. Diagnosis front disconnect, right?

I replaced the disconnect and installed a new actuator. The disconnect had no splines left on the shift collar. It was toast. While I was in there, I swapped out both cvs, and a leaking front diff seal. I got everything back together and hit a dirt road around the corner, and the front still wouldn't engage! I still have low range, but without the front axle.

I can hear both motors working. I run through the flow chart again. Right front tire up in 4hi, tire spins freely, driveshaft spins also! Both front tires up in 4hi, the passenger side tire turns freely, turns the driver side tire(opposite direction), and driveshaft. Right fornt tire up in 4lo, tire tuns with resistance. Well I fixed the disconnect.

The next day when I started the truck, the 4wd switch on the dash said the t-case was in neutral. It wasn't I could pull forward and back. I put the tranny in neutral and heard the encoder motor turn. The light over 2hi light up (it was not flashing before) and the truck drove fine. This happens every time I mess with the 4wd switch now. The day after trying the switch (not the next engine start) it either says it's in neutral and/ or trying to shift to a4wd. Sometimes all the lights on the 4wd switch flash after start up, until I shift the tranny to neutral. No matter what the dash switch says the truck will drive in 2wd.

Any idea what direction I should go? Start throwing parts at it, (4wd switch, TCCM, encoder motor) or is my t-case done?

[ErikSS]

The switches are a known problem. I would throw a New one in for diagnostics. Worse case you would have a spare. I got mine from a Carquest.

[DirtyBacon04]

4wd switch is what i was thinking, too.

[ErikSS]

My local Carquest is $26.99 and the part number is 5320726.

[bartonmd]

Likely a switch. Turn the vehicle off and turn the switch all the way back and forth about 20 times. Cleans the resistor. Mine went back to normal after I did that.

Mike

[Glasscaster]

Thanks for the input guys! I'll try to put in a new switch this weekend. I did the turn the switch trick, no luck. I'm still confused that I have 2wd low range. Have others had this same failure before? I know there are clutches in the T-case that send power to the front. Would a failing switch shift the low range collar without engaging those clutches?

[Trail X]

This issue pops up once in a while. Try the flow chart again with the truck on and the switch in the a4wd setting. There are three components to the transfer case selector motor, the motor and gearset, the encoder, and the position lock. When in 2wd, 4hi and 4lo, the tccm sets the motor position and locks the lock, then basically doesn't monitor it anymore except to monitor the encoder, and report back status through the switch lights. If the lock isn't working, the motor can easily drift out of position and the friction avaliable though the front driveshaft clutch plates gets greatly diminished. The a4wd mode is different from the other modes in-that the tccm constantly monitors the slippage and the encoder position, and constantly adjusts the motors position accordingly, never locking the transfer case motor, and in your case - keeping the tc locked up.

[Glasscaster]

Well I popped in a new switch last week and no luck. I installed the switch, turned the ignition to the on position, and heard one of the motors make a quick zip zip. Feeling brave I flipped it into 4hi, put it in reverse, and pulled back about ten feet (turning the steering wheel left to right). It felt like the front was locked up or trying to. I even felt a bit of binding in the steering.

Thinking every thing was sorted out, I took it down the dirt road, with it in in 4hi. I pulled off into some deep sand on the side of the road and stopped, and hit the gas hard enough to break traction. I went back to look at the tire marks and only the back tires spun. I tried two more times with the same result. Took her home and went through the flow chart.

With either front tire up the tire spins and spins the drive shaft. With both front tires up either tire will spin the drive shaft, but dose not always turn the opposite side tire (or the opposing tire will spin very sluggishly now). Things seem to be locking up better in 4lo (including the front diff). There is a lot more resistance when trying to turn the tires when they are in the air. It still won't work in the dirt though. I've tried the flow chart with and without the motor running in all 4wd modes.

I have a friend with a high-end scanner, maybe he can shed some light on this issue. I hope the front diff isn't going out...

Thanks again for the input every one!

[Trail X]

Did you not read my response? I'm 99% sure that the encoder motor lock is your issue. Put it in A4WD mode, keep the key in the on position, and try the flowchart again (engine may or may not have to be running, I am not sure).

[Glasscaster]

Yeah James, I did read your response. I also read through several posts, about issues similar to mine, before posting. IIRC someone stated on GMT that it is almost impossible to tell if it is the encoder lock or the clutches in the t-case without a professional grade scanner?

I tried the A4WD mode, with the key switched to on, and with the truck started. It didn't lock up. The only time it tries to lock up is in 4lo. Going through the flow chart in 4lo, the passenger side tire is much harder to turn. Once or twice the front locked up in 4lo, but then unlocked when I tried a different 4WD mode.

I'm going to lift all four tires today and see if the front has any activity at all.

Thanks again for reading and responding!

[Trail X]

That's disappointing to hear that it still isn't locking up in a4wd mode. I have yet to hear of a case among us on ortb where the transfer case clutches have worn down and are no longer providing any friction.

Before digging into or getting a new transfer case, I'd try one last test that would simulate poor traction on the rear tires. I might try lifting the rear axle up and putting it directly on some wood, rear tires in the air, and see if you can pull the truck off the wood in any of your operating modes.

The tccm needs to see slippage before it knows to engage more clutch when in a4wd mode. I'm wondering if simply turning the front wheels by hand while stopped isn't tricking the system enough to make it engage.

Based on history, it's much more likely an issue with your encoder motor, and less likely your clutches.

[tarsh]

Mine did the same. Ended up the tcase. I did actually pull my encoder off and open it up, tons of little gears in there. Just change the case. I git mine drom a salvage yard for 200$ . Worked like a charm. If thats not it then you have a spare. I too followed james flow chart. It help narrow alot but couldnt put my finger on it. So i went for it.

[Glasscaster]

Bingo James!
"The tccm needs to see slippage before it knows to engage more clutch when in a4wd mode. I'm wondering if simply turning the front wheels by hand while stopped isn't tricking the system enough to make it engage."

I had no wood to stack under the truck, but I put it on four jack stands. None of the 4WD modes sent power to the front, except A4WD. Things still were not good though. The front locked up after about five seconds of free spin, and unlocked again. The front continued to lock and unlock randomly and violently, until I hit the brakes and switched it off. The locking/unlocking was violent enough that I thought the truck was going to come off the stands.

It's good to hear that the t-case clutches are not know to fail often, gives me more confidence that a used one would be GTG(if I need one).

Thanks guys

[Trail X]

Kinda makes sense that it would be rather jumpy if the encoder motor lock didn't work. If the lock isn't working, then the system likely cannot keep any compression on the clutch plates. My guess is that as soon as the encoder motor adjusts and adds compression to the clutches, it then gets backed off by the internal clutch plate forces.

Replace the encoder motor assembly. The 4WD transfer case uses the 7 pin motor for the New Process 226 (rpo code NP8).

[Glasscaster]

I know it's been a long time since this thread has been discussed, but I thought it would help some folks to confirm this problem solved.

I replaced the encoder motor and all is well, not at first though...

I swapped out the encoder motor with a new one, and the service 4WD light came on. The 4WD switch also no longer worked at all. I sent the part back, thinking it was defective. I received a replacement and the same thing happened. With the original encoder motor reinstalled, the switch came back to life and I could hear both motors under the truck turning. I'm very frustrated at this point! I start over with the flow chart. Out of total curiosity I swapped the front axle disconnect motor for the original, and every thing worked! It was a combo of the encoder motor and the disconnect motor being bad.

Regards,
Jason

[Trail X]

Wow, double whammy eh? Its rare that two parts go bad at the same time.

[v7guy]

Very very peculiar, glad you got it figured out, you definitely got thrown a curve ball on this one!

[Glasscaster]

Yup, it was a project...
The front disconnect failed in the snow, on a 45 degree inclined switch back (going down). This is where my adventure began! When I replaced it, I put in a new dorman actuator also. That front disconnect actuator/motor must have failed pretty quickly. By the Time I put on the new t-case encoder motor, (THANKS JAMES!)it was trash. Luckily the original off of the old disconnect still worked fine. So you could call it a triple whammy. Front disconnect, t-case encoder motor, and front disconnect actuator!

Thanks for all the help! This truck never saw the inside of a mechanic's garage for this issue. I am sure it would have cost me 5 times more if it had.