Smoked something nasty while in 4-wheel drive

[MacLaddy]

Hi Folks,

I have a '99 Limited with about 200,000 miles. It has the locker package and the two four wheel drive options (multi-mode transfer case?). I either lock it in 4 hi/lo or I can push the button for a part time effect.

We had an ice storm a few days ago. I started off locked in 4-hi, as the road condition was treacherous. I drove on the freeway for a while in this mode until the roads started drying out a little. I could feel it binding up, so I got off the freeway, shifted out of 4-hi and backed up to disengage. I pushed the button for the part time mode and got back on the freeway.

It drove fine for a while, as it always has in this mode. A few miles later, it felt like it was starting to bind up again (which it shouldn't do). Unfortunately, I wasn't in a place to get off the freeway for a few miles to disengage entirely. When I finally did, I noticed an awful, natural gas burning smell coming from the vehicle. I pulled over, shut it down, and watched with dismay as smoke emerged from under the hood.

I can't tell where it was coming from. The drivers side near the frame had clearly been sprayed with some type of fluid and was smoking like crazy. No obvious fluids were low, so I'm assuming some kind of transfer case event? I let it cool off, and finished my drive in 2wd. No more issues or smoke.

4wd still works, but now it stinks like a skunk. Even walking around it after its been shut down for two days. Any ideas? Did I smoke the transfer case?

 

[Malcolm99]

The Tcase only holds about a litre of oil so I would check the fill plug to see what level it's at and do a drain and fill, maybe the front driveshaft to tcase seal failed, if it's been leaking awhile one might not notice, but it's sounds like you lost a lot of fluid quickly. It should have 75w90 in it but it usually smells similar to your discription.

 

[Kanoe]

If it is around and on the drivers front inner fender area it is likely the front diff breather tube.

There have been periodic threads about this over the years, one being mine. It seems sometimes when operating for an extended period in 4x4 the front diff pukes gear oil out of its breather tube which makes a mess.

Consensus seems to be that after a person does a drain and fill on the front diff, an extended 4x4 rip causes it. Mine did it once the first time I used 4x4 for more than an hour. Some have said the diff is overfull but that's pretty hard to do.

Just check your level and see its still in the good range.

 

[JohnMc]

When I drained and refilled my front diff (routine maintenance) I did the usual (correct???) method of refilling to the fill-hole level, same as on pretty much every other gearbox type gizmo. And it puked a bit of oil out of the breather the next few times I sued 4WD for any extended amount of time. And yes, it pukes out on the drivers side of the engine - the breather's end is clipped to a holder underneath the fuse block.

Maybe oil jsut gets slung on it when being operated at speed, so when it warms up and tries to breathe out, it pushes some oil with it? Dunno. Mine did the puke thing a couple of times, then stopped.

 

[T4R2014]

What is part time mode? You are either referring to 2WD or 4HI unlocked, neither of which should bind even on dry pavement.

 

[phattyduck]

Also, you can shift *out* of 4WD or unlock the center diff at any speed - no need to stop. Shifting into 4WD and/or locking the center diff have speed limitations (different depending on transfer case versions).

-Charlie

 

[MacLaddy]

If it is around and on the drivers front inner fender area it is likely the front diff breather tube.

There have been periodic threads about this over the years, one being mine. It seems sometimes when operating for an extended period in 4x4 the front diff pukes gear oil out of its breather tube which makes a mess.

Consensus seems to be that after a person does a drain and fill on the front diff, an extended 4x4 rip causes it. Mine did it once the first time I used 4x4 for more than an hour. Some have said the diff is overfull but that's pretty hard to do.

Just check your level and see its still in the good range.

Thank you. I searched for the breather tube issue and confirmed the location. It looks like it pops up right in the area that is now covered in oil. I haven't gone back out to check to see if it came from the tubes, but this now seems to be the clear solution. I'm still not sure about the smell though. I am guessing I smoked the oil.

When I drained and refilled my front diff (routine maintenance) I did the usual (correct???) method of refilling to the fill-hole level, same as on pretty much every other gearbox type gizmo. And it puked a bit of oil out of the breather the next few times I sued 4WD for any extended amount of time. And yes, it pukes out on the drivers side of the engine - the breather's end is clipped to a holder underneath the fuse block.

Maybe oil jsut gets slung on it when being operated at speed, so when it warms up and tries to breathe out, it pushes some oil with it? Dunno. Mine did the puke thing a couple of times, then stopped.

How does it smell when that happens? Mine stinks now, even after sitting for a couple of days. I know some fluid burned on the exhaust, but the smell seems excessive.

 

[MacLaddy]

What is part time mode? You are either referring to 2WD or 4HI unlocked, neither of which should bind even on dry pavement.

I had an old '75 Dodge PowerWagon with a limited slip transfer case. I believe they called it part time 4wd, so that adage has stayed with me. I'm guessing my 4Runner is essentially doing the same thing when I push the button but don't shift the transfer case?

Also, you can shift *out* of 4WD or unlock the center diff at any speed - no need to stop. Shifting into 4WD and/or locking the center diff have speed limitations (different depending on transfer case versions).
-Charlie

Not mine. It will bind up something bad when I lock in the shifter. So much that it will occasionally unbind in a rapid jerk/slip, especially when I go from dry to ice. Maybe this is pointing to an underlying condition? Over the last few years it has gotten bad about disengaging. It won't come out unless I back up.

 

[FD7683]

I would start with the basic drain and fill service if the transfer case stinks. I also shifted the 4WD knob to other functions and also got a small grind. My locker didn't even turn on and kept blinking.......

 

[twitchee2]

if its binding and jerking on dry pavement but not on something "slippery" you mights have different ratios in your diffs. How long have you had the rig? Do you know what ratios you have?

 

[cas5259]

Why would extended periods of 4WD cause gear oil to shoot out the front diff breather? Unless it’s very overfilled, I don’t get it. You’d think the rear would be prone to this too, given they’re similar parts, and the rear is always in use.

The only thing I can think of are sporadic clogs, just enough to build up a little pressure, and then boom it shoots oil all over. Does anyone have some more specific info?

 

[gamefreakgc]

It's possible your e-locker was added later by someone. If that's the case, you might have 4.30 gears in the rear and 4.10 in the front.

 

[Malcolm99]

It does seem strange.

 

[T4R2014]

I had an old '75 Dodge PowerWagon with a limited slip transfer case. I believe they called it part time 4wd, so that adage has stayed with me. I'm guessing my 4Runner is essentially doing the same thing when I push the button but don't shift the transfer case?

You are more than likely confusing it with a full time transfer case. Pressing the button is 4HI unlocked. Moving the lever locks it. Unlocked still provides a viscous coupling to make up for the open center diff.

 

[MacLaddy]

I would start with the basic drain and fill service if the transfer case stinks. I also shifted the 4WD knob to other functions and also got a small grind. My locker didn't even turn on and kept blinking.......

Agreed. The more I read up on this, the more I am convinced I didn't cause any permanent damage. I'll have the transfer case and front diff oil changed.

 

[MacLaddy]

if its binding and jerking on dry pavement but not on something "slippery" you mights have different ratios in your diffs. How long have you had the rig? Do you know what ratios you have?

It's possible your e-locker was added later by someone. If that's the case, you might have 4.30 gears in the rear and 4.10 in the front.

The rear locker is standard equipment for this year. It's one of the reasons I chose this model. I'm fairly certain the ratios are correct, as this is a new issue for me. It has never done this binding up before when I push the button.

I see today that one of my front tires is pretty low. I don't think that would cause it, as the front diff obviously isn't locked, but I'm otherwise out of ideas.

 

[MacLaddy]

You are more than likely confusing it with a full time transfer case. Pressing the button is 4HI unlocked. Moving the lever locks it. Unlocked still provides a viscous coupling to make up for the open center diff.

Interesting. I hadn't heard of a viscous coupling before. So this coupling transmits the torque but allows for some slip if it's needed? Is this coupling only for the front axle, or does it apply to both? Does moving the lever engage a non-slip gearset or chain?

I need to read up on this.

Edit to add: Thanks for the introduction. I found this link that provides a good explanation. Viscous Coupling | awd cars, 4x4 vehicles, 4wd trucks, 4motion, quattro, xDrive, SH-AWD, Haldex, Torsen, wiki - How it works

 

[Bad Luck]

The rear locker is standard equipment for this year. It's one of the reasons I chose this model. I'm fairly certain the ratios are correct, as this is a new issue for me. It has never done this binding up before when I push the button.

I see today that one of my front tires is pretty low. I don't think that would cause it, as the front diff obviously isn't locked, but I'm otherwise out of ideas.

The rear diff locker was never standard equipment on any 4Runner. It was always an additional option from the factory. Airbags are standard (they came in every trim of 4Runner) but rear diff locker was not standard (not every 4Runner received one).

 

[MacLaddy]

The rear diff locker was never standard equipment on any 4Runner. It was always an additional option from the factory. Airbags are standard (they came in every trim of 4Runner) but rear diff locker was not standard (not every 4Runner received one).

Semantics. It was a standard option. Not really important to the conversation.

 

[phattyduck]

Semantics. It was a standard option. Not really important to the conversation.

The question is whether your truck was equipped with it from the factory or not and if a diff was replaced at some point to the wrong ratio.

Most/all of the rear locker 4Runners are 4.3 ratio front/rear and most of the rest are 4.1 front/rear - so if either the front or the rear was replaced on its own, there could be problems.

There is no viscous coupler in the 3rd gen multi-mode transfer case. Later transfer cases did have a viscous coupler in some configurations. If you are feeling any binding in "AWD" mode (four green wheels lit, no center orange light), there is a problem with your 4WD system. Even on dry straight roads, you should feel no binding or odd behaviors in locked 4WD (orange light - you would feel it when turning and that should be avoided).

-Charlie