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Transfer case Question

Discussion in 'Chevy Trucks' started by Sydenstricker Landscaping, Jul 20, 2009.

  1. Sydenstricker Landscaping

    Sydenstricker Landscaping PlowSite Veteran
    Messages: 3,882

    Okay I have the push button 4x4 on my truck. I dont know if this is normal or not but here goes. When I had my front diff and u joints serviced, when you spun the front drive shaft, it also spun the rear. The wheels are disengaged when in 2hi and it shifts into 4hi just fine. Didnt think the front shaft was supposed to spin with the back, even in 2 wheel. On my Blazer, which is floor shift, you can spin the front drive shaft freely with in park and all 4 on the ground. It shifts thru 2hi to 4low no problem. Is this something I need to address or just leave well enough alone?
     
  2. millsaps118

    millsaps118 Senior Member
    Messages: 694

    If I'm understanding your question correctly, you have something going on that shouldn't be.

    When you switch from 4hi to 2hi do you hear or feel the Tcase unlock or disengage? I would road test it at a slow speed (5-10mph) and listen and feel for it to unlock. The way you described this, sounds to me that your Tcase is still locked up partially.

    I have a 02 2500hd and when my indicator says 2hi, only my rear wheel spin when I have it up in the air on a lift. When I switch to 4, all will spin.

    BTW Chevy's do not have a front differential, they have a Transfer case. Did you get the fluid changed as you were referring to getting it serviced? If so make sure they used the recommended fluid and weight that GM calls for and also the correct amount. If these are off (either one) this could very well be your problem. GM Tcases, trannys, and rear diff's are very picky about what gets put inside them and how much, If you don't have the right fluid and amounts in them they will act up.

    Hope this helps.............
     
  3. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    Chevy's absolutely have a front differential, as well as the transfer case. Gear oil in the front and rear diffs, Synthetic manual transmission lube is your best bet for the case. Do a search for "misting"

    With the case in 2HI, you should be able to climb under the truck and spin the front shaft, not the rear shaft. In 4HI or 4LO you should not be able to spin either.
     
    Last edited: Jul 20, 2009
  4. Sydenstricker Landscaping

    Sydenstricker Landscaping PlowSite Veteran
    Messages: 3,882

    I think the Tcase still stays in 4x4. The front wheels unlock, when on the lift, the front wheels did not move, but the front drive shaft would spin if you spun the rear drive shaft, but not independently. By serviced I mean, u joints, new fluid and yes it is the proper weight and levels, greased, etc. Just basic general maintenance. Not to start or cause an argument, but yes the Chevy's do have a front differential. Even says it is a front diff in the manual. The transfer case is behind the transmission. Maybe they call it different things in different areas, but I call it the front diff. Thank you for the help

    The truck is a 2000 Chevy 2500 4x4 Silverado (NBS) 6.0 4L80E trans with push button 4x4
     
  5. Clint S

    Clint S Senior Member
    Messages: 280

    If you have the "auto" 4x4 button you must use per Chevy the SAF-T TRAC fluid. This is due to the clutches in the auto case all others is just ATF. I think the trac fluid is green
     
  6. Sydenstricker Landscaping

    Sydenstricker Landscaping PlowSite Veteran
    Messages: 3,882

    Yeah it has the auto 4x4 button. I think the fluid is the blue stuff, but I could be wrong
     
  7. millsaps118

    millsaps118 Senior Member
    Messages: 694

    My fault I had my head up my ass....so your saying that you can spin the front drive shaft coming off the tcase and your rear drive shaft will also spin but NOT your front wheels? If this is the case you could have a bad encoder motor or shift module that is not allowing the front drive shaft to completely release. This is mounted on the outside of the Tcase by the front shaft, if you take it off you can manually lock and unlock it by using a pliers.
     
  8. Sydenstricker Landscaping

    Sydenstricker Landscaping PlowSite Veteran
    Messages: 3,882

    LOL it is Monday, always a head up the ass day:D That is exactly what is going on with it. The front wheels dont move, but everything else does, even in 2 wheel.
     
  9. Clint S

    Clint S Senior Member
    Messages: 280

    Yeah come to think of it is is blue, just do not put regular ATF or gear oil in it as it will cause problems with the clutches. Not really knowing, but could this be due to it being and Auto t case
     
  10. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    If you try shifting the case manually after removing the encoder, use a wrench. Crescent wrench (metric, of course) or the proper size. My 243 uses a 14 mm. Pliers could damage the shaft making it difficult to put the encoder on. I forgot you have the Auto-Trac. Sounds like it's stuck in Auto 4Hi to me.
     
    Last edited: Jul 20, 2009
  11. millsaps118

    millsaps118 Senior Member
    Messages: 694

    OK...so it's a good chance it's one of the 2 I just mentioned. You can test this by unbolting it off the tcase and manually locking and unlocking it. Look for a black box bolted on the outside of the tcase towards the rear (by the frt drive shaft/yoke) with a wire harness plug. You might have to take the frt shaft off to get the shift module/Encoder out but once you have it off, look inside (your tcase) and you should see a lever/switch, flip it and grab the yoke and spin it. If you unlock it it will spin freely. If you lock it, you will feel it grabbing gears.

    The shift module/encoder basically replaced the "old school" shifter that use to be located in the cab on the floor. Everything is just controlled electrically now, but you can still test it easily with no special tools.

    GL
     
  12. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    There's nothing wrong with your T-case Tom. The 246's don't completely disengage from the front diff even in 2WD. It's operating as intended. wesport
     
  13. PLOWMAN45

    PLOWMAN45 2000 Club Member
    Messages: 2,832

    the fluid is blue for the t case and there are front diff i have them serviced
     
  14. Sydenstricker Landscaping

    Sydenstricker Landscaping PlowSite Veteran
    Messages: 3,882

    Ah probably due to the Auto 4x4 function. That seems like it would waste gas turning all that extra mass constantly. I think when/if I get a new truck to replace this one, it will be floor shift. Thanks B&B!!:waving:
     
  15. William B.

    William B. Senior Member
    from S.E. IA
    Messages: 978

    You know with the floor shift it is still electronically controlled right? The HDs and 1 tons do not have the auto trac transfer cases in them like the LD 2500s and the 1/2 tons do.
     
  16. PLOWMAN45

    PLOWMAN45 2000 Club Member
    Messages: 2,832

    well it 2000 they did have the badge that said hd but build sheet is 8600 gvw hd same as 01-09
     
  17. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Correct Tom, its' due to the 246 and it's "auto" position, not just because of the fact that it's push button controlled. Lots of push button equipped trucks do not use the 246 hence they have no auto position.

    So you don't have to look for the floor shift 4WD with your next truck to avoid it. Just need a truck that isn't equipped with the 246.
     
  18. Sydenstricker Landscaping

    Sydenstricker Landscaping PlowSite Veteran
    Messages: 3,882

    I thought about yanking the front drive shaft out for the summer, then put it back in towards winter. Figured that may save the extra wear on the front some. Why the heck would they put autotrack in a friggin 2500 plow prepped truck?? Oh well just something I will just have to live with, lol. Would be nice if I could relatively easily swap in a NP205 or something on the back of the 4L80E
     
  19. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    It sounds logical but it doesn't make a difference. There's no measurable MPG increase to running it with the front shaft removed. But you'll sure hate yourself for not having it the first time you get stuck in a soft spot. :realmad:


    A 205 is actually possible as guys have done it but a 241 is 10 times easier. I didn't say easy, but easier. Big difference. :D
     
  20. Sydenstricker Landscaping

    Sydenstricker Landscaping PlowSite Veteran
    Messages: 3,882

    LOL I like easier, but I bet it still would suck. I think leaving well enough alone is the most viable option now. The place I go to dump grass and get mulch, etc gets pretty muddy and nasty after some good rain. I can see myself getting stuck with my crappy Goodyear tires