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four wheel drive won't stay engaged

Discussion in 'Chevy Trucks' started by mcwlandscaping, Feb 28, 2008.

  1. mcwlandscaping

    mcwlandscaping 2000 Club Member
    Messages: 2,557

    Got the old style thermal solenoid thingy up front. Earlier in the middle of plowing the truck just went out of 4hi on its own, luckily was on last place. Well, then it worked again and i was plowing this past evening, then right on cue getting to the hilly accounts, the truck just goes out of 4hi into 2wd and i can't get it back in. I still have a bunch of accounts to do and a big storm coming on friday...help please

    -mike-
     
  2. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Was you able to determine if it was the actuator kicking out, or the T-case itself kicking out Mike?

    Guess you didn't get the Posi-Loc on it yet?
     
  3. mcwlandscaping

    mcwlandscaping 2000 Club Member
    Messages: 2,557

    the t-case is shifting in and out like it should...luckily my posi decided to work this evening or else i wouldn't have gotten home!
     
  4. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    So your relatively sure it's the actuator still giving you the fits?

    I know you fooled with the actuator itself before so I'd first see if you have 12V getting to the actuator when the T-case is engaged.

    Only way to know for sure that the signal is first getting to the actuator is to get under it with a test light and start checking wires. Should have a brown wire that starts at the switch on the dr side top of the T-case and heads forward to the connector plug on the axle tube. Should have power in that brown wire when in 4WD. If it doesnt see if you have it going in the switch. If you do, then the switch is failing.

    If you not familiar with the switch, it's threaded into the top of the T-case just above and behind the encoder motor. This is the switch that sends the signal to the actuator to engage. It's tripped internally by the internal T-case linkage.
     
  5. mcwlandscaping

    mcwlandscaping 2000 Club Member
    Messages: 2,557

    Thank B&B, you're just the guy i was hoping would be on here! :) I'll check it out, i'm hoping it'll work for a bit longer now so i can finish what i need to get done....this truck is turning into a royal PITA.

    thank you!!!

    -mike-
     
  6. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    If you get into a jamb and really need the 4WD before you get it resolved here's a little tip I learned a long time ago...

    Look around for some type of spacer, it needs to be exactly 7/8" long. Some lug nuts are the perfect size/length for example. Maybe even the ones on your truck. ;)

    1) Jack the truck up until the right front wheel is off the ground.

    2) Unscrew the actuator out of the diff.

    3) Insert your "spacer" into the hole.

    4) Gently thread the actuator into the hole while slowly turning the right front tire.

    5) You should be able to "feel" the axle engage while threading the actuator in and turning the tire. Dont force it, if it wont go unscrew it and reposition the spacer just a bit.

    6) The spacer simply holds the engagement collar in on the axle shaft, thus replacing the job of the actuator and locking the inner and outer axles together.

    7) The axle will now be engaged for as long as you need it. You can leave it in as long as you want without hurting a thing. It's just like running an older truck equipped with manual locking hubs in the "engaged, or lock" position.

    If your going on a road trip though, I'd take it out. Still wouldn't hurt anything if you left it in, but it's a bit hard of fuel mileage with it engaged all the time.
     
  7. Spitz

    Spitz Senior Member
    Messages: 192

    They make an updated part for your old "donkey dick" actuator. Some axles wont accept it but it worth a shot to check it out.. Like said you'll have to check for power and the actuator itself.. 9 out of 10 times its the actuator failing.. The new actuator doesnt disengage when the ignition power is off like the older style.. The updated part comes with a new harness to install it, but its only one wire.
     
  8. mcwlandscaping

    mcwlandscaping 2000 Club Member
    Messages: 2,557

    Well, we got through the last few accounts and will be taking the truck to the shop where the front end was fixed the first time either a little later today or tomorrow morning...i should be fixed by tonight...i really don't want to use my spacer again, that was such a pita! :) This summer it will be converted to the cable manual engagement kit, i'm sick of this electric crap! lol, thanks for the help guys

    -mike-
     
  9. BlueLine Ent

    BlueLine Ent Senior Member
    Messages: 570

    Im beginning to think that after seeing all your threads about all the different grief this truck is giving you, it may be time to trade up. Seems for all the time and money you've probably put into it, you could have grabbed yourself a decently new rig. Just my $.02.
     
  10. mcwlandscaping

    mcwlandscaping 2000 Club Member
    Messages: 2,557

    Totally agree, but, it's just not in the cards right now, come mid to end of spring i'll be doing that. But to get another truck AND set it up to plow is just too risky now money wise...ide like to keep this truck as well considering how much ive put into it and that i'm going to need a backup/second truck this year for landscaping/lawn care operations
     
  11. mcwlandscaping

    mcwlandscaping 2000 Club Member
    Messages: 2,557

    Update for you, truck is in the shop now, guy ive known forever and trust. He says that a module (i'm guessing the one in/on the T-case) is starting to fail causing this problem...does that make any sense?
     
  12. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    The term "module" is a bit of a generic term Mike. Could be referring to the T-case encoder motor on the side of the T-case or the actual TCCM module which is the "brain" to control the encoder motor/4WD operation. The TCCM is located under the left side of the dash. Either one could cause a failure of the 4X4 operation. Both can, and do go bad.
     
  13. mcwlandscaping

    mcwlandscaping 2000 Club Member
    Messages: 2,557

    ok...i'm not sure which one it is. Is the motor what engages the T-case? If so, i doubt that's it because that always worked even when the front wasn't getting engaged. I just know it's getting fixed now so i'll have it for tonights storm...probably will be paying it off as i plow tonight :( lets see if i can go tonight without breaking anything!!

    Thanks B&B, i'll let you know what happens later on when i get the truck back!
     
  14. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    The motor is what shifts the T-case.

    If your positive the T-case was actually engaging correctly when you were pressing the 4X4buttons, then you don't have an encoder motor or TCCM problem as they're the components that are used to shift the T-case.

    Sounds to me like you still have a front diff actuator or wiring problem.
     
  15. mcwlandscaping

    mcwlandscaping 2000 Club Member
    Messages: 2,557

    Ide go through and change out the wiring harness but i have every intention in the spring of getting the manual cable engagement for the front diff . I just need this electric crap to last me til the end of the winter! B&B, i really want to fly you up here this year to have you go through my truck!!! lol I trust you with my truck more than anyone i actually know in person!
     
    Last edited: Feb 29, 2008
  16. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Might be cheaper to haul your truck down here Mike.

    Have a close friend who drives truck (flat bed) that travel up your way every week.
    Could get ya a good shipping rate.


    Got a loading dock nearby? :D
     
  17. mcwlandscaping

    mcwlandscaping 2000 Club Member
    Messages: 2,557

    Actually several!! :) That would be so cool if that could happen, after i get a new(er) truck we could have my truck brought down there, i would love that though! We'll see as better weather approaches :-D

    Anyway, i got the truck back, not entirely sure but something with the sending unit for that front actuator. The actuator is now on a seperate switch to power it, a lot more stright forward operation! :)

    Thanks guys for the information! B&B, we'll be in touch soon i'm sure with the next truck problem next time plowing!!
     
  18. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    That "sending unit" is the switch I was describing in my original post Mike. They basically just bypassed it with a toggle. So your problem is in the switch or the hanrness that engages the actuator. And I'm sure is the very parts/parts that have been giving you all these problems for a long time. Nothing wrong wit bypassing it with the toggle. But you can still fix it corecctly at a later time if you want. Or of course you can always install the Posi-Lock as well at a later date. :)
     
  19. mkwl

    mkwl 2000 Club Member
    Messages: 2,361

    I know this is an old thread, but I'm wondering- will this work on the newer ('01 and up) 2500HD's? My 4x4 is working okay (knock on wood)- but just in case...
     
  20. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    You remembered this one Matt. Good for you and yes it works on the later trucks too you just have to remember to disconnect the actuators electrical connector while you're using the spacer trick. It's located right on the axle tube toward the passenger side. No tools are needed to disconnect it.

    Although the newer ones seldom need the trick as they're of a much better design so they're actually reliable. So if you lose your 4WD someday it's normally the switch panel or T-case encoder motor that causes it rather than the axle actuator. But a good tip to know regardless.