4x4 Won't Engage

[monteheeren]

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

[sevenslotgrill]

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.

[rjeffery]

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.

[Evansamms]

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

[monteheeren]

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

[sevenslotgrill]

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.

[monteheeren]

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

[monteheeren]

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

[j cAT]

Originally Posted by MONTEHEEREN

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.

[monteheeren]

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

[MT-2500]

Originally Posted by MONTEHEEREN

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

[j cAT]

Originally Posted by MONTEHEEREN

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.

[monteheeren]

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

[16th hippy]

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.

[monteheeren]

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.