'04 Bla er won't go into 4 hi

[Monkeyman]

'04 Bla er (sorry, "last letter" key broke...new keyboard on order) w/90k miles. 2 hi is fine and it will shift well into 4lo. When I hit the button for 4 hi, the buttons flash but stays in whatever it was previously in (2 hi or 4 lo). Since it goes into 4 lo without a hitch, I'm assuming this is an electrical issue as opposed to a mechanical issue, but I'm not a mechanic and don't know for sure. With 12" of snow forcast, I could sure use 4 hi although I'm only 5 miles from work so if I absolutely have to, I can muddle through with 4 lo.

Does anyone have any experience with these trucks and/or this 4wd set up? I could try a new switch but this one is only about 3 years old and rarely gets used so I'd sort of doubt it would go bad this soon.

Any help would be appreciated. (I think my next truck will have one of those nice, mechanical levers on the floor. One less thing to go wrong.)

[cnc]

Sorry Chris the last time I had one of those trucks it was a standard with locking hubs and a separate stick for the transfer case.
Just guessing here but besides the switch it could be a solenoid or what ever shifts it into the 4H range.

[Roy1965]

Is it a S10 or a Trail Blazer?

[Sin City Stan]

I have a Yukon with sounds like the same system. The lights sometimes don't indicate the true condition. Kind of like the gear indicators on the Nomads and Vaquerro's. Are you sure it stays in Lo Lock? I realize it should be obvious but the question has to be asked.

If you're stuck in Low try this. http://www.gm-trucks.com/forums/topi...ck-in-4wd-low/

Good Luck, it sucks to work on vehicles in the Winter.

[ponch]

I have a 2009 Suburban and it has a transfer case shift motor. No lever at all. It has the dickens of a time getting into 4Lo. What I had to do is put the transmission in neutral and it will go into 4Lo, but not in Park. I hate relying on a shift motor, but I guess the lever takes up room and people are lazy and stupid, but I have heard of the motors breaking and there is a module for it too. May be you should put a scanning tool on the car and see if it throws any powertrain codes. That said, may be changing the transfer case fluid wouldn't be a bad idea. It probably could use it.

[Rasta]

Remove battery to remove battery tray to see it the mechanism is moving to shift it into 4hi. when you push 4hi. The shifter cable on these freeze up some times...some had vacuum hoses so make sure the vacuum hose is not cracked or disconnected.

[dan313]

I have the same issue. Check out this link I found on You Tube.


Lenny

[ponch]

The thing is, it goes into 4Lo, not 4Hi, so I imagine the vacuum diaphragm works.

[Rasta]

Originally Posted by dan313

I have the same issue. Check out this link I found on You Tube.


Lenny

I didn't watch the video but that's the mechanism I was talking about.

[Monkeyman]

Thanks, guys.

roy --- It's the S10 version.
Stan --- When it shows it's in 4Lo, it's definitely in 4Lo. Probably couldn't do 40 mph wound out. When it shows 2Hi, I can't get much traction in my driveway (that I haven't shoveled) so I'm sure there are only 2 wheels (actually, 1 wheel) spinning.
ponch --- The truck only shows one code (as of a couple months ago) for the purge valve solenoid (whatever that is). I don't think that has anything to do with the 4wd system although I could be wrong. You're absolutely right about changing the t-case fluid. That's on my list for the spring.
dan --- I've seen that vid. Like ponch said, since it goes into 4Lo, I think that's probably ok. I might have even changed that at one time.

One thing someone on another board thought was that it could be the encoder motor. From what I've read, either it unplugs and after removing 3 bolts, it comes right out OR you do all that then have to remove the front drive shaft. I'm not knowledgeable enough (nor do I have the right tools) to do that.

[Sin City Stan]

Originally Posted by Monkeyman

Thanks, guys.

roy --- It's the S10 version.
Stan --- When it shows it's in 4Lo, it's definitely in 4Lo. Probably couldn't do 40 mph wound out. When it shows 2Hi, I can't get much traction in my driveway (that I haven't shoveled) so I'm sure there are only 2 wheels (actually, 1 wheel) spinning.
ponch --- The truck only shows one code (as of a couple months ago) for the purge valve solenoid (whatever that is). I don't think that has anything to do with the 4wd system although I could be wrong. You're absolutely right about changing the t-case fluid. That's on my list for the spring.
dan --- I've seen that vid. Like ponch said, since it goes into 4Lo, I think that's probably ok. I might have even changed that at one time.

One thing someone on another board thought was that it could be the encoder motor. From what I've read, either it unplugs and after removing 3 bolts, it comes right out OR you do all that then have to remove the front drive shaft. I'm not knowledgeable enough (nor do I have the right tools) to do that.

Motor encoder, Shift motor or pushbutton module are all covered in YouTube. Maybe not necessarily for your exact model but Chevy / GMC trucks/SUVs are pretty much standardized for parts and functions. Just go to YouTube and start searching.

[Monkeyman]

Originally Posted by Sin City Stan

Motor encoder, Shift motor or pushbutton module are all covered in YouTube. Maybe not necessarily for your exact model but Chevy / GMC trucks/SUVs are pretty much standardized for parts and functions. Just go to YouTube and start searching.

I've searched on YouTube and found a bunch of good videos relating to "fixing" those things but I don't want to start spending money replacing parts I don't need to replace. Good to know most of the Chevy/GMC trucks are similar.

[Sin City Stan]

Originally Posted by Monkeyman

Good to know most of the Chevy/GMC trucks are similar.

They're built in the same plant. Only difference is the badging, trim and a few options & colors. But, essentially the same vehicle.

[dan313]

Did you check out the video on the on the vacuum hose valve thats on the transfer case. Could be the problem.

Lenny

[Monkeyman]

Originally Posted by dan313

Did you check out the video on the on the vacuum hose valve thats on the transfer case. Could be the problem.

Lenny

I think so. (I've watched a couple do en vids in the past day or so.) Most of the vids show HOW to fix things but not necessarily how to DIAGNOSE the issue. Like I said, I don't want (and can't afford) to spend money replacing ALL the possibly bad parts. I can see spending a grand to find that all my problems were caused by a $4 part.