4x4 Won't Engage

[MT-2500]

The front axel actuator motor is on right side of front axel.
A black plastic part that screws in and out.
It has a wiring plug in and the inside end of it has a plunger that pushes the front axel shift fork that locks the front axels together.

First check is the see if the front drive shaft is locking in in 4W drive.
In 4W it it should be locked in and you can not rotate by hand.

[monteheeren]

Bought a new front axle actuator motor and still don't have a 4x4. Same problem. Push 4 HI, can hear t-case move into 4x4, reached under the truck to see if the front drive shaft was in gear and it was, couldn't turn it. The 4 Hi push button just blinks. It will not go solid. This truck is driving me nuts!

Monte

[j cAT]

Originally Posted by MONTEHEEREN

Bought a new front axle actuator motor and still don't have a 4x4. Same problem. Push 4 HI, can hear t-case move into 4x4, reached under the truck to see if the front drive shaft was in gear and it was, couldn't turn it. The 4 Hi push button just blinks. It will not go solid. This truck is driving me nuts!

Monte

if you read my posting 01-10-08 8:37pm it explains what you descibed earlier about how you were told that the encoder transfer case motor was bad and i gave some instuctions as to replace this . now you changed the front dif motor. this does not engage 4x4.......

[MT-2500]

Also did you check to see if the front drive shaft is locking in.
It has to lock in for front axel to pull.
MT

[monteheeren]

J cat, How can the encoder motor be bad, if I can hear it engage, and the front drive shaft is engaging? With the truck in 4 HI, I crawled underneath and tried to turn the front drive shaft. It is INGAGED already.
Unless it has an electrical contact that is not talking to the front axle actuator. I have a hand held code scanner, and did not find any codes. Took the switch out of the dash to look for bad solders. Everything looks great.
The owners manual has a sequence to put the transfer case into neutral mode. Push 2 HI and 4LO at same time for 10 seconds, the hit Reverse and then Drive, then turn off key. The red light will come on and stay on on the switch. I do not have the auto 4x4 option, only 2Hi, 4HI, and 4LO. To get transfer case out of neutral, turn on key, and hit 2HI. Can't see how the encode motor can be bad if all this works.
Monte

[monteheeren]

Found out I have an NP263XHD transfer case.

[MT-2500]

Originally Posted by MONTEHEEREN

Found out I have an NP263XHD transfer case.

On that one I do not have much info on it and my electrical diagram posted is down.

If front drive shaft is lockng in.
Your problem is in front actuator motor or wiring or switching circuit to it.

Older ones you could ground pin 13 on diagnostic connector and get codes but not sure it will work for the 263 transfer case.

When shifted to 4W the transfe case switch should switch and engauge the front axuator motor and extend the motor plunger to lock front axel in.

Make sure it is getting all power to it.

For wiring and more info on it the All data sub or a factory repair manual would be your best bet.
All data sub is 24.95 USA $ plastic and about 5 minutes setup for a one year on line sub.
Lot of repair info and repair flow charts and wiring diagrams.
http://www.alldata.com/products/diy/index.html

Good Luck MT

[777stickman]

IMHO! The blinking push button lights are telling you that the encoder-motor is not going to the selected position. The motor sends a feed-back signal to the TCCM (Transfer Case Control Module) and then to the switch panel. Even though you can hear the motor working I don't think is getting to the position it needs to be in.

Another possibility is that the motor is going to the selected position but the internal switches are not sensing that position to send the feed-back signal to the TCCM. If that's the case the TCCM will not send the signal to engage the front axle.

A hand held scanner will not get into the t-case control module system.

[monteheeren]

Thank you for all the information. I'm kind of in a bind. Can't get the truck out of the garage unless I have 4x4. All I have is a hand held scanner, and I guess it will not scan for the transfer case codes. Did a lot of research last night and it sounds like I need a new encoder motor. Found a Technical Service Bulletin about the 2002 year had problems and they suggest replaceing the encoder motor and have a new program installed. Should I bite the bullet and put a new encoder motor in? I found one for $254. If I get the 4x4 to work, I can drive it to get a new program loaded into it. I do have one live wire at the front axle actuator. It must need more than one wire hot to move the actuator.
Monte.

[777stickman]

I cannot suggest you change the encoder-motor. All I can do is provide you with my opinion of what may be the cause of your trouble. The TCCM and the wiring between the TCCM and encoder-motor could also be suspect.

The electronics in todays vehicles allow technicians to actually see what's happening in circuits with the high end scanners.

I replaced the encoder-motor and the TCCM on my '98 Sub only to find out I had a bare wire shorting out the T-CASE fuse.

I guess if I was in your position and had the money to burn for a "shotgun" try, I would start with the encoder-motor. If it doesn't fix it you'll always have a good spare like I do.

As far as the one hot wire at the front actuator the TCCM may provide the ground to complete the circuit. (just a guess).

Let us know.

[16th hippy]

sorry been away for a few days....a buddy got locked up and i was trying to get him out. with all fuses good, and hearing the encoder trying to work, would say it's the sensors in it. there are no sensors in the x-fer case itself, all that is in the motor, and those signals are sent to the TCCM. as i said before, i prefer to replace entire assembly instead of replacing just the sensors in there.

if you can get x-fer case into neutral with switches, do that(SET PARKING BRAKE). lift truck if needed. remove the small splash gaurd with the 4 bolts that is under the x-fer case. remove the 4 bolts holding front driveshaft to front axle. use flat bladed screwdriver to gently pry rubber boot with metal ring(rotate shaft snd pry on other side). keep that going until boot is all the way back, and then remove front driveshaft. encoder motor is on side of xfer case, now very visible. unplug electrical connector. remove the bolts holding it onto the xfer case. encoder will now come off.(save the gasket). put gasket on new encoder, and intstall.(if you couldn't get the xfer case into neutral, then you will have to put it into nuetral by hand) use pliers(GENTLY). the shaft end is tough, but you don't want to mess it up. you will have to align it by eyeball, but it's not that difficult. once that is done, install new encoder on xfer case. tighten bolts, and install rest of stuff in reverse order of removal. start truck, engage into 2WD. you may hear some unpleasant sounds come from xfer case, scares the shit out of me everytime, but it's just the gears engaging. done it this way many times, and NEVER had a single problem. let us know how it goes.

[MT-2500]

Originally Posted by MONTEHEEREN

Thank you for all the information. I'm kind of in a bind. Can't get the truck out of the garage unless I have 4x4. All I have is a hand held scanner, and I guess it will not scan for the transfer case codes. Did a lot of research last night and it sounds like I need a new encoder motor. Found a Technical Service Bulletin about the 2002 year had problems and they suggest replaceing the encoder motor and have a new program installed. Should I bite the bullet and put a new encoder motor in? I found one for $254. If I get the 4x4 to work, I can drive it to get a new program loaded into it. I do have one live wire at the front axle actuator. It must need more than one wire hot to move the actuator.
Monte.

I would go for the All Data sub first and get the wiring diagrams and shifting test or repair flow charts first.
24.95 $ is a lot cheaper than 254$ plus.

If the front actuator is in instead of out or extended.
You could take a stack of flat washers about 5/8 thick or a big nut and put them in the housing where the actuator screws in and get the front axel fork locked in.

For a test to lock in front axel and to get it out of garage.
But remember 4W is not for driving on a dry payment.
Good luck MT.

[monteheeren]

A lot of great information. Think I'm going to try the washer trick, just to get the truck out of the garage. I'm going to take it to someone that has a scanner that can check the codes. I'll repost when I find out more.
Monte

[monteheeren]

Finally found the problem. I took the truck in to a shop that had a scanner and found out it was a bad encoder motor on the transfer case. The old encoder motor was locking in the front drive shaft, but it was not sending the right signal to engage the front axle. To get the truck out of the back yard, I took out the front actuator on the front axle, and put in a large nut about 1/2 inch thick, and then installed the actuator. That way, I could force the front wheels to engage. Truck came out of the yard with no problems. The shop installed a new GM encoder motor for the low low price of $971.00. OUUUUUUCH! Sure wish I had a Tech2 scanner but those darn things cost $5000.00. Anyway, I'm back on the road! Yea!
Thank you for all your posts!
Monte Heeren

[j cAT]

Originally Posted by j cAT

if you read my posting 01-10-08 8:37pm it explains what you descibed earlier about how you were told that the encoder transfer case motor was bad and i gave some instuctions as to replace this . now you changed the front dif motor. this does not engage 4x4.......

that was expensive fix . but at least you got in to the repair shop . now just keep that transfer case fluid maintained properly........