Weird rubbing noise in 4wd mode?

SouthernSilveradoGuy85 · May 3, 2016

No it's not.

In 2wd the front diff and the transfer case are not turning.

I believe if you have an electronic transfer case where the knob as an auto function then the front driveshaft is always spinning even in 2wd, at least in auto. Also since the front driveshaft is spinning the front diff will also be spinning just like the rear, but the hubs won't be locked. This is at least how I understand an auto 4x4 system is like.

redwngr · May 3, 2016

I believe if you have an electronic transfer case where the knob as an auto function then the front driveshaft is always spinning even in 2wd, at least in auto. Also since the front driveshaft is spinning the front diff will also be spinning just like the rear, but the hubs won't be locked. This is at least how I understand an auto 4x4 system is like.I thi

My understanding is/was that it's the other way around - with the auto system in 2wd mode, the front axles are engaged and the front wheels are driving the diff, but the front driveline is disconnected at the transfer case.

When 'auto' kicks into 4wd it engages at the transfer case to complete the driveline power flow.

SouthernSilveradoGuy85 · May 3, 2016

My understanding is/was that it's the other way around - with the auto system in 2wd mode, the front axles are engaged and the front wheels are driving the diff, but the front driveline is disconnected at the transfer case.

When 'auto' kicks into 4wd it engages at the transfer case to complete the driveline power flow.

Think about it though. It would be a lot less stress on the whole drivetrain if the front driveshaft spun all the time and when 4hi comes on in auto it's less stress and just need to lock the hubs. With an auto 4x4 system it needs to be able to go into and out of 4hi very quick so the driveshaft needs to already be spinning. If it took as long for it to be put into 4hi in auto than it takes if you turn the dial or shift in the floor to 4hi yourself then there would be advantage to auto 4x4. And if it has to get the driveshaft to start spinning then it would take as long as manually putting it in 4hi. In regular 2wd it may not spin, but in auto the driveshaft will spin. It may even spin either way. One day I might look at the driveshaft in 2wd and auto 4 to see for myself, that is if it's not raining.

redwngr · May 5, 2016

With the front shafts already engaged, the drive shaft would be spinning, since the front diff would be driving it.

With it connected at the transfer case and the 1/2 shafts disconnected, the drive shaft would be turning, driven by the transfer case.

Either way the front drive shaft and front diff will be turning, hence the auto mode parasitic loss referred to in the OM.

FL335i · May 5, 2016

isn't the front diff spinning even in 2wd? It's CV's hooked to the diff. the auto mode clutches are in the transfer case. That I do know.

SouthernSilveradoGuy85 · May 6, 2016

isn't the front diff spinning even in 2wd? It's CV's hooked to the diff. the auto mode clutches are in the transfer case. That I do know.

I still have yet been able to look at mine in 2wd and auto since it's been raining all week. But, and I know they're different TCs, the front drive shaft didn't spin in 2wd on my old '98. I'm just assuming that the front driveshaft in my '14 spins all the time in auto, but not sure about in 2wd so it may or may not in regular 2wd. Plus I'm pretty sure they still use locking hubs which means the half shafts shouldn't spin unless it's in 4x4. Unless they've changed and they have something different in the front diff itself that does the same thing.

FL335i · May 8, 2016

With no manual hubs the CV's are spinning all the time, no matter what the Tcase is in. Hence the front diff must be spinning all the time also. I think on my '94 4Runner there was a vacuum hose that ran down the diff, which engaged the spider gears or something like that.. I don't know. I know I saw what looks like a electric motor on the passenger side of our diffs. That might be something that disengages the the pinion so the front drive shaft does not spin in 2wd.

SouthernSilveradoGuy85 · May 8, 2016

With no manual hubs the CV's are spinning all the time, no matter what the Tcase is in. Hence the front diff must be spinning all the time also. I think on my '94 4Runner there was a vacuum hose that ran down the diff, which engaged the spider gears or something like that.. I don't know. I know I saw what looks like a electric motor on the passenger side of our diffs. That might be something that disengages the the pinion so the front drive shaft does not spin in 2wd.

The electric motor you saw was probably for the steering since these 1500s have electronic rack and pinion. Tomorrow I'll be able to look under my truck while a buddy is in the driver seat letting it roll forward so I'll see what all spins in 2wd and auto 4. I'm just curious by now lol.

FL335i · May 8, 2016

Yes, you are probably correct! Forgot about elec ps. Let us know man.

SouthernSilveradoGuy85 · May 8, 2016

Yes, you are probably correct! Forgot about elec ps. Let us know man.

Neither the front driveshaft or the half shafts on the front axle moved while in both 2wd or auto. I was expecting one or both to turn at least in auto, but maybe he let the truck roll forward before it finished the switch to auto. So I guess neither moves unless it's in full time 4x4 or in auto when the ECU tells it to put it in 4. So seems like everything is done in the transfer case and they still have auto locking hubs, at least from what I can tell.

As for the OP, I've never had an issue when not using 4x4 for an extended period of time. When I had my '98 the only thing I would do is go to the boat landing near my house since it was gravel at the time and just tested to make sure 4x4 engaged in late Fall for the Winter. For the 10 years I had that truck ('04-'14) I never had a problem with the 4x4 other than 1 time and that was just the switch in the dash that went bad. So never had any of the actual mechanicals not work. And I did put that through hell which included mudding at least 1 or twice a month. As long as you abuse the truck too much and change the gear oil in the axles along with fluid in the transfer case then it should last the life of the truck without any problems. For sure now adays since GM seems to have beefed up the drivetrain in the past few years.

Edited May 8, 2016 by SouthernSilveradoGuy85

J-Doc · May 9, 2016

I can't believe this thread is still going.

kstruckcountry · May 9, 2016

The axle is engaged by an actuator on the right hand side. The CV's always spin.

SouthernSilveradoGuy85 · May 9, 2016

The axle is engaged by an actuator on the right hand side. The CV's always spin.

It must be a lot of slack then cause I only had my buddy let the truck roll for a couple inches and neither the half shafts or front driveshaft moved while in 2wd or auto 4. At least that's how it is on my '14.

Edited May 10, 2016 by SouthernSilveradoGuy85

redwngr · May 10, 2016

isn't the front diff spinning even in 2wd? It's CV's hooked to the diff. the auto mode clutches are in the transfer case. That I do know.

No. it doesn't spin in 2wd.

The front axles each have disconnect and there is a disconnect at the transfer case.

In 'auto', it will be spinning.

And of course, it turns in 4wd.

jaydomazz · January 30, 2022

On 5/2/2016 at 7:32 PM, FL335i said:

J-Doc. This is my first 1/2 ton 4WD. I've had a lot of toyotas and even a F250. None made the "rubbing" noise you described. But yes, if you are on dry pack, pavement etc in 4wd it will make the "rub" noise. I work in construction, large sites. I use Auto 4wd more than anything. I get the rubbing noise even on some good dirt roads when in 4 hi. But the more you use it the less noise it makes. I'll admit, I'm a experienced rock crawler, SAS'd 4runner, run Detroit lockers and it alarmed even me. Just the way these more modern systems operate. Everything is tighter. I have 44k on my truck and the noise is about half what it was when new. I changed my diff oils this past weekend and tried 4wd today on the job. even more quite. In short... NORMAL. Do not drive on good traction surfaces with any 4wd. Use the Auto 4wd. 4WD is for real-deal sand, mud etc; Loose surfaces.