4x4 Won't Engage

Bought a 2002 Silverado HD 2500 8100 allison trans last summer.
Push button 4x4 will not work. I'm corn fused! The push button worked last summer. Now its winter, and when I needed it, it would not work. The 4 Hi light blinks, but the 4x4 will not engage. Got stuck in my backyard in the snow. If I select 4 Lo, same thing. The light just flashes and won't engage.
Could it be just a fuse? The truck only has 32K on it.

Monte Heeren
(515)238-4927

Not sure what t-case is in those but what is happening is when you push the button, there is an electronic controller(not sure of the proper name) that has contacts in it and it is supposed to turn and make contact and then you are in 4wd. It is in the t-case. So, what is happening is it is not making contact and will need replacement. Sometimes they get rusty or something if they are not used much. I am not a ASE certified mechanic or anything, and it is hard to tell from here, so get a second opinion.

Try this FIRST. for 4 hi be rolling forward about 2 mph like in your driveway and push the 4wd button and see if it engagues. Also try it in 4lo but you need to be stopped and a/t in neutral and then push the 4low button and put a/t in drive. Check your owners manual if you have one as it should have instructions.

A common problem is the contacts in the switch breaking. Many people have resoldered/replaced the switch to fix. May not be your problem, but is a cheap easy place to start.

Dunno if your problem is anything like mine, but I've got a 2000 Silverado Ext Cab, Long box, with the 5.3. My 4x4 works(ed) fine all summer, spring and fall. Now, on real cold mornings, she wont shift in/out of 4. Hit the switch, blinks, then goes b ack to original setting. If i run her for about 10 min, then let her sit for a couple minutes (kinda heat soaking in my mind), she'll start to work fine again. I'm assuming theres a little water in somewhere that's freezing up an actuator or something. I did some running in about a foot of slush a week or so before this started happening (darned maritime weather). If she doesn't shift, at least I know I can wait 10 min and she will.

Evan

Thank you to all that replied.

I will try the rolling at 2 mph trick. Trouble is, I can't get the truck out of the yard! Its parked in my garage, but there is a lot of snow and ice in the yard.
I tried to get the truck out of the yard for about 45 minutes. The temp outside was about 40, so I don't think it was an ice issue.

What is a t-case?

Monte

monte.....t-case = transfer case

Your 4wd high will engague easier when you are moving forward and push the button. That is why I suggested pushing the button when you were moving forward in your driveway.

Sevenslotgrill,
I'll try it when I get the truck out of the garage.

Ready to sell the SOB. Checked the fuses and they were ok. Crawled underneath and everthing is pluged in and looks good. When I hit 4 HI, it sound like its going into 4x4, but the light keeps blinking. Backed the truck out of the garage and have it stuck in about 6 inches of mud. The dam truck won't go into 4x4. What a piece of crap. Can you tell I'm pissed off. I paid big bucks for this truck and I can't use it.
Monte

Ready to sell the SOB. Checked the fuses and they were ok. Crawled underneath and everthing is pluged in and looks good. When I hit 4 HI, it sound like its going into 4x4, but the light keeps blinking. Backed the truck out of the garage and have it stuck in about 6 inches of mud. The dam truck won't go into 4x4. What a piece of crap. Can you tell I'm pissed off. I paid big bucks for this truck and I can't use it.
Monte
replace the 4x4 switch, my switch failed at 30-40kmi. the solder joints were defective. but if the switch did have this defect should throw service 4x4 light. also make sure transfer case has oil in it up to bottom of top fill hole. fluid is blue . called tracII if no fluid get at dealer only. cost of switch is 25-30.00. transfer case can't be bad if vehicle really has 32kmi......put in auto 4x4 as this will engage as soon as slip is detected.

Was told the actuator in the trans case needs replaced. Do you have to drain the trans case to do the repair? Does anyone have a diagram of the transfer case. 2002 Silverado 2500 HD Allison trans.

Monte

Was told the actuator in the trans case needs replaced. Do you have to drain the trans case to do the repair? Does anyone have a diagram of the transfer case. 2002 Silverado 2500 HD Allison trans.

Monte

Check all fuses in both fuse boxes. There is 3-4 of them.
Your best bet is to get it on a transfer case/transmission /engine capable scanner and get the code and see where the problem is.
Lot of shifting test can be run on a good scanner
Post back any code no.
What engine size and what transfer case no?
Are you sure they were not refering to the actuator motor on front axel?
Also check wiring on front axel. Sometimes they get knocked off.
MT

Was told the actuator in the trans case needs replaced. Do you have to drain the trans case to do the repair? Does anyone have a diagram of the transfer case. 2002 Silverado 2500 HD Allison trans.

Monte
the atc fuse goes to the transfer case shift control module,this then goes to the transfer case motor encoder. if they got code that this motor is bad it could be any of these parts. did they disconnect the 4 wire connector and measure a-b 2ohms a or b to ground 10k ohms. dtc 0308,0309,0310,0315,0323,0324, if the dash mode switch were bad i don't think it would fail to attempt engagement. the encoder motor is mounted on the forward side of tranfer case drivers side this is where the 4 wire connector goes in. removal of shields,wiring connector,3 bolts,reuseable rubber gasket,when installing make sure encoder shaft lines up properly with transfer case shift shaft.align detent of case mount and encoder mating surface detent. torque to 30ft lbs. good luck....how much to replace at dealer? make sure they will guarantee that this is bad. replacement of transfer case fluid tracII is recommended every 30-40,000mi.

Thank you for the reply. Checked all fuses in cab and under hood. All ok.
Did not check the wires on the front axle. This truck has the 8100 engine. Do not know what transfer case it has. Does it have a tag on it that I can tell? There are no messages or codes that flash on the dash. I don't have access to a scanner at the moment because the truck is back in the garage. The is about 6-8 inches of mud outside the garage door. Can't get truck out unless I have 4x4. Isn't the electric motor on the transfer case called the actuator motor? I thought the electric motor on the transfer case did all the work. What is the thing on the front axle? What does it do. Do they work together? Sound like a red neck don't I. Have not checked any wires on the front axle. Will do that tomorrow night and repost.
Monte

the actuator on the front axle engages it, and only it(and the front hubs). the enconder motor on the tranfer case is what shifts it into 4WD. most times the contacts in the motor can be replaced, but if slightly higher age/mileage, or you just have the extra money, i recomend you replace the enitre encoder. is on the driver side of transfer case. if turns out to be bad encoder(actuator) motor, and if you need some tips on easier ways to replace it, just ask, i will make a small write up that will help you. no pics though..lol.

This forum is awesome! Thanks for the info.
Do you have any instructions on how to replace the front axle actuator?
Is the front actuator like the old manual locking hubs. Is it what actually locks the front wheels into 4x4?

Monte.

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.

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

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.......

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

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

Found out I have an NP263XHD transfer case.

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

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.

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 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.

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.

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.

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

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

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........

Will do!

Monte

Just a note. The code set was DTC C0327 Encoder Circuit Malfunction.

Still wish I had a scanner to pull the code myself.

Monte

Monte
You are welcome for the thank you.
And thanks for posting back how it went and the fix.
And a big ouch on the 921$ repair.
Glad you got it fixed.
The code 327 is encoder motor electrical circuit.
Sometimes it takes a encoder motor to fix it.
For future reference for anyone that has the 327 code.
A lot of dealers are repairing/replacing the encoder motor resistors to fix a lot of the code 327 problems.
Good luck
MT