4 wheel drive question

Motodox · May 4, 2015

Hello have a question on the 4x4 on my truck. When I push 4 wheel low or high I can hear the transfer case switch but I can't tell if the front wheels are engaged. I can feel the truck is in a low gear being that it's real torquey and slow, does this mean my transfer case locks in correctly?

When I turn the truck I don't feel anything different, you know that grabbing feel you get in the wheel when u turn sharp in 4 from the front tires being locked in. I don't get that. Does this mean something in the transfer case or something with the front differential?

Motodox · May 4, 2015

I also took off on gravel with it in 4 lo and 4 hi only the rear tires are spinning. Light on the 4wd switch shows that it's in 4wd . Light flashes when switching then stays on like normal.

CapitalTruck · May 5, 2015

Could be that the transfer case is working right but the front differential isn't hooking up. Does the 4wd light on the dash come on? (Do trucks of your year have a 4wd light on the dash?) I ask because with the GMT-900's the dash light coming on corresponds with the actuator in the front differential doing its thing. It closes the circuit for the light.

gmtech4 · May 5, 2015

Do the above and then scan it for codes

If you're getting low range the tcase IS in low range ., front diff engaging is another story hence the scan required if the feeling of front axle not gripping

Motodox · May 5, 2015

Alright, when I push the 4wd button the light near the button flashes then stays on like the tcase has locked in 4wd but I don't have any lights on in the dash. My truck has that little square lcd screen on the left of dash but it doesn't show anything just flashes security when I have the door open. No check engine lights and no 4wd light in the dash. Do I have to drive the truck for a little to get that actuator on the front diff to lock in?

And if I don't have any lights on can I still scan it?

Motodox · May 5, 2015

I'll check after work if my truck has a dash light. I should be able to just turn the key and see it light up before I start the truck correct? And if I do have a 4wd light in the dash and it's not coming on then maybe it's that's front actuator is bad maybe.

CapitalTruck · May 7, 2015

What's the verdict?

Motodox · May 8, 2015

What's the verdict?

Thanks for staying interested capital, unfortunately I have not been able to test much cause the tranny is out and battery cables are undone. So I can't check for dash lights but I've done a little research and I believe I only have the light next to 4wd button, not positive yet. Stay tuned because I just got the call today the tranny is done so I'm picking it up tomorrow and putting it in on Saturday. So I should have more answers. I really hope the transfer case is good and it's just something minor with the front diff locking in. Like a bad actuator.

Motodox · May 10, 2015

*update*

Alright I got the fresh tranny in, everything on the motor has been gone through with all new gaskets fresh intake new sending unit all wiring harnesses and clips are together as they should be. Fresh fluids valvoline max life 5w-30 in motor, all new dex VI in the auto trans, auto trAk II in the transfer case, 80-90 valvoline front diff 75-90 syn. rear diff.

Truck is still up in the air, fired up and is runnin great oil pressure is right at 45 at idle and comes up to 60 when on the throttle. All gears go in smooth. And No LEAKS !!! I'm so happy after all the hard work of cleanin and replacing gaskets on this nasty 215k miles Silverado. Now looks great and runs great.

Now back to the 4 wheel drive. I believe I have just the light by the button that comes on when selected in to 2wd-4hi-4lo. I hear the transfer case switch and light flashes then stays on as it should. I put into drive (remember truck is still in air tires off the ground. I look down the front drive shaft is spinning and one front wheel is . I can hold one still and vise versa.

My question is, is this front diff supposed to be locked in direct wheel to wheel? Like I shouldn't be able to hold one wheel still. Like I said a few post ago when I drove the truck and took a sharp turn I can't feel any grab in the front wheels. I'm still unsure if my 4wd actually works. Or if I should have a 4wd indicator on the dash lcd display.

WilliamBos · May 10, 2015

These trucks are really only 3 wheel drive, only one front wheel actually spins.

A locker would be nice.

intheburbs · May 10, 2015

Front axle is an open diff, so yes, you'll be able to hold one wheel while the other spins.

Yes, a locker would be nice, but a 3-wheel truck is more than sufficient for 99% of drivers out there. The hardcore offroaders are likely going to upgrade the axles anyways.

Personally, I've never gotten mine stuck, and I've had it in some pretty silly places. Took a pass on Metal Masher, though...

BlackZ71Silverado · May 11, 2015

Front axle is an open diff, so yes, you'll be able to hold one wheel while the other spins.

Yes, a locker would be nice, but a 3-wheel truck is more than sufficient for 99% of drivers out there. The hardcore offroaders are likely going to upgrade the axles anyways.

Personally, I've never gotten mine stuck, and I've had it in some pretty silly places. Took a pass on Metal Masher, though...

A 3 wheel drive?? That's not right. If your 4x4 truck is "3 wheel" as you claim, something is broken.

You obviously don't know how the four wheel drive system, transfer case, or differential work. The open diff. allows both of your tires to spin at different rate, independent of each other.

Both of your front tires should spin when four wheel drive is engaged, mine always have, on all of my GM trucks/SUV's.

Most likely not at the exact same rate but they should both turn in four wheel drive.

MikeNH · May 11, 2015

This whole three wheel drive is the biggest pile of BS on forums from people who don't understand how differentials work.

OP, trying to test it by putting the truck in the air will give the stability or traction control fits so disable that prior to doing this again. Power will go the path of least resistance so to try and get power to transfer to the other tire you need to *carefully* put a load on the front tire that is spinning. I usually did this by holding a breaker bar or long ratchet extension sideways and gently applying it against the spinning tire. This won't work if you have real aggressive tires as it'll just rip the tool out of your hands.

Motodox · May 11, 2015

Ok sounds like everythin is workin as it should, I guess I'll really find out if I ever use or need the 4wd.

intheburbs · May 11, 2015

A 3 wheel drive?? That's not right. If your 4x4 truck is "3 wheel" as you claim, something is broken.

You obviously don't know how the four wheel drive system, transfer case, or differential work. The open diff. allows both of your tires to spin at different rate, independent of each other.

Both of your front tires should spin when four wheel drive is engaged, mine always have, on all of my GM trucks/SUV's.

Most likely not at the exact same rate but they should both turn in four wheel drive.

Yeah, I've only owned five different 4WD vehicles, and have been offroading for over 20 years, but sure, I have no idea how they work.

The differential allows the two wheels to spin at different speeds. Hence the name. But in a low-traction situation, an open differential will send all the engine's power to the wheel that's slipping, leaving the wheel with traction motionless. I like the way Marisa Tomei explains it in "My Cousin Vinnie."

So, since I have no center differential on my trucks, the front and rear driveshafts are linked together and spin at the same speed. My trucks also have the G80 locker in the rear, so if one rear wheel slips, the locker engages. So, therefore, I have a 3 wheel drive truck because of the open differential in the front.

If only one of my front wheels has traction (meaning both rears and one front wheel are slipping), I'm stuck. A 4wd vehicle with two open diffs can get stuck if one of each front and rear have no traction, and a rwd or fwd vehicle with an open diff will get stuck if one drive wheel loses traction.

I like this video, because it shows how a typical 4wd vehicle is really 2 wheel drive: