Need schooling: Full Time 4WD 101

[JpAdct]

Sorry for the extended post, but I'm partially blowing off steam here too. :rant:

I finally got my 2006 4Runner home Friday night after days and days of research and decision making. Thanks for all of the advice and encouragement on this site by the way. Saturday morning, we called one of the local dealerships to see if they had any service appointments available for the timing belt service. I didn't think $800 for the timing belt, water pump, two camshaft seals, a crankshaft seal, and drive belt was too bad. This has 101k on the odometer and I didn't want to take chances if it had never been done. I just sucked it up and accepted that I'd have to buy the belt (V8) as soon as I bought the truck. So the dealership has it, I tell them I just bought it and I want to check on any major services it might need, plugs/diff fluids/tranny fluid/Xfer case fluid/etc, but if they tried selling me any air freshener or blinker fluid, I was DONE.

So the service adviser calls me a little later in the day and said all my fluids look good and they're not going to change them, other than the rear differential fluid, it needs to be changed. I asked the million dollar question, "well if it's a full time 4wd, then why wouldn't both differentials need changing at the same time? And why wouldn't we change them at the same time regardless of how the front looked, just so I know they are on the same interval? He asked the "lead tech" who said "that thing's not full time 4wd." I responded by saying, "well whatever Toyota calls it, but it's a different drive train system than the V6 because it has a 2WD option on the transfer case shift selector and my V8 does not. I was told I was wrong which I clearly knew was BS. I have seen my switch and I have seen the switch of the V6 models which can be manually put into 2WD. Not to mention the excellent education I get from this site! I told them to proceed and I would call them back.

I called another local dealer and told them I was worried about where my truck was currently because they didn't agree my V8 was a full time 4WD design. I was told by them, (after they had to ask others in their shop), "No, it's not full time 4WD." Now I'm baffled and burning up the iPhone trying to find an answer quick since I wasn't near my home computer. Most of what I read called it a full time 4WD with the center differential lock option button. Only a couple of websites called it a smart system that engaged itself when it needed traction. SOOOO, I'm thinking maybe this makes sense, yeah, it's a smart system. OK I can buy that.

So I go back to the dealership to get some belongings out of my truck since they didn't bother to check for parts before they tore it down (another nightmare that lead to me getting a free rental car for a few days and another ulcer). I told the service adviser that I needed somebody to explain this system to me since I cannot not stand owning a vehicle that I don't understand the basic components of. He says, "well you stirred up quite the friendly debate between our service manager and our lead tech about whether this is full time 4WD or not." I responded with some smart @$$ comment about the service department should know better than anybody else. Sorry, couldn't help myself. Bear in mind, I am in Florida where 4WD's are not as common, but they are still here and I would expect the techs to understand this system!

So I spoke with the "lead tech" who was working on my truck, and I explained to him about the V6 model having the 2WD option on the selector switch. He responded by saying, when he had my truck in the air, pushed the gas, only the rear wheel was spinning, that is NOT indicative of full time 4WD. So I suggested that maybe it was the smart system and since there was no resistance on the front or rear wheels, the 4WD system did not engage itself. This might be the dumbest thing I ever said, since zero friction would be the same as slippage in the rain or snow, I don't know. So we all agreed to do more research on this. I can't believe I am the first person to raise this question at this very well known dealership since these things came out in 2003. Unfrigginbelievable!!!

I get home later that night and I'm reading over the VIN decoder paper work the service desk gave me. You know, the sheet that tells me the options and equipment of my vehicle based on the VIN information. Right there it is, black and white, under MECHANICAL & PERFORMANCE: Full Time 4WD. This is listed right under Torsen(TM) Locking Center Differential and Down-Hill Assist Control/Tow Package.

So, do I make them change both differential fluids, or do I rest easy knowing they checked them, and the front looks good along with the transfer case and transmission??? Can any of you fine people explain this system to me in a manner that my pea brain can identify with? I might need small words and pictures too just in case I have to go back to the service department where I live and explain this to these well trained technicians.

As always, thanks and GOD Bless.

 

[chaz]

its refferred to as FT4WD to set it apart, since, as far as i know, no AWD vec. have a 2 speed transfer case.this may help, should tell ya what u want. http://www.toyota-4runner.org/4th-gen-t4rs/68991-how-does-all-time-4x4-work-v8.html http://en.wikipedia.org/wiki/Four-wheel_drive http://www.toyota-4runner.org/off-roading-home-monst4rs/7583-awd-vs-full-time-4wd.html

 

[DC Dude]

Gosh, all this pain just to figure out whether to change the front differential fluid? I had all 3 fluids changed for $120, and that means $40 for your stress.

Just get'er done so that you won't have to come back.

 

[scottm]

I changed my diffs and T-case fluids last night at 71k, bought this truck a year ago. The diffs were both black and runny, the magnetic drain plugs had a thick coating of metallic sludge. The T-case fluid was honey amber and no magnet on the drain plug.

I run in rear-wheel-drive all summer, don't know what the previous owners did. The front should be changed when the rear is changed, always, regardless of AWD or part-time 4WD.

 

[M1911]

The V8 is full time 4WD.

 

[jwyshrek]

4wd, 2wd, AWD is irrelevant. If you want something done to YOUR vehicle and are willing to pay for it, then it should be done. End of story.

Just make sure they do it...I'd watch them like a hawk. Not necessarily at Toyota dealerships, but I've heard stories of place charging for work that wasn't done.

If it were me...I'd put some markers on the drain and fill plug before taking it in...

Actually, if it were me, I'd just do it myself...

 

[scottm]

Actually, if it were me, I'd just do it myself...

I still haven't decided if it's really worth it to do everything myself. If I didn't enjoy it, I might have better use for all that time, and the garage space and money my tools take up.

 

[jwyshrek]

Know what you mean...but it is the only way to make sure it is done right.

However, changing gear oil might be the exception. I haven't done it yet on my 4Runner, but have done it on my Jeep XJ.

Thanks God, Toyota has drain plugs...should make it easier and less messy. Ugh, that gear oil smell!...smells like puke.

 

[scottm]

Ugh, that gear oil smell!...smells like puke.

What? I like the smell of an opened engine or gear box, my brother was over and said the same thing. I guess I associate it with doing something I like to do.

Last night it took me a couple hours to drain and fill my gearboxes, lots of setup and cleanup involved. On a lift with a pump this might have taken 15 minutes. Probably a lot less if I did it regularly. So it's hard to justify doing it myself from a time standpoint. I still have to do my Land Cruiser, that will probably take half the time now that I've just done my 4R, plus it sits up a lot higher.

 

[G.I.G.]

As I understand it, most of the power goes to the rear wheels under dry/normal operating conditions with the full-time 4wd. I know Jeep sometimes refers to it as "on-demand" 4wd but it's basically the same principal.

I agree that you should just have all 3 boxes done. When I changed mine at 30k, the rear was the dirtiest, but the front was pretty cloudy as well. The center didn't look as bad. For the money, it's cheap insurance just to have all of them done, even though the rear probably needs it the most.

 

[FourEyedWilly]

I still haven't decided if it's really worth it to do everything myself. If I didn't enjoy it, I might have better use for all that time, and the garage space and money my tools take up.

I have to agree. One smell in this world that I CANNOT stand is gear oil. Having over $2k in tools saves me $300-400 bucks each time I guess but I wonder the same.

To add to that, my father was killed by a car falling off of jack stands. Doing something he loved but it makes it hard climbing under the car. I do in fact love working on my rigs, but every now and then I have to take some pretty deep breaths...and multiple jack stands, blocks, e brake, floor jack, tires. :wink2:

Sometimes, I think it's best to have someone else do it. Trust is hard to come by though, especially when we all have a VERY good understanding of our toys sometimes better than even the dealer.

 

[scottm]

I've always easily slid under my Land Cruisers for most work, just did my 4R diffs and T-case without jacking it, just sucked it in and slid under. Even my daughter's quattro and my son's Impreza I can do oil changes without jacking them up. Laziness is keeping me safe!

 

[FourEyedWilly]

I've always easily slid under my Land Cruisers for most work, just did my 4R diffs and T-case without jacking it, just sucked it in and slid under. Even my daughter's quattro and my son's Impreza I can do oil changes without jacking them up. Laziness is keeping me safe!

Ha ha I agree. It's why I buy 4 wheel drives, so I can fit under them. Ha! He was under a 32 Coupe, at least it was a pretty car. (of course it's probably haunted now)

To the OPs point though, it is very frustrating when a dealer can't catch a clue.

 

[G.I.G.]

I've done all the work on my 4Runner (oil changes, changing gear oil, lube driveshafts, installed rear diff breather, etc.) without jacking it. That is one of the nice things about an SUV. Now that I have a lift, it's even easier :biggrin2:

The thing that I do not like about changing gear oil is the huge mess. I've done it twice now (once on my 4Runner, and once on Leftyguns21's 4Runner) and no matter how careful I am trying to line up the pan, pump in the new oil (which they need to make better pumps for, BTW) and fill it up with out loosing too much, it always gets everywhere. It's an easy job for the most part, but a messy one. Where is Mike Rowe when you need him!

 

[scottm]

I have one of those giant cookie-pans from Autozone under my oil drain pan, caught all the drips, minimal mess. Used a lot of blue paper towels though.

 

[M1911]

I've done all the work on my 4Runner (oil changes, changing gear oil, lube driveshafts, installed rear diff breather, etc.) without jacking it. That is one of the nice things about an SUV.

Mine isn't high enough for me to get under it easily, so I use ramps.

 

[JpAdct]

So I got both differentials done for the obvious reasons. I was just confused (the original reason for this post) why I was being told only one needed it and just exactly HOW this full time 4wd system works. I got my OEM owners manual from eBay in the mail yesterday and according to the maintenance schedule in that, they are only to "inspect" the differential fluids every 15,000 and to change as needed. I have that now so I will be able to keep a better eye on what needs to be done. Thanks for all the thoughts and input. If anybody feels like chiming in with some more details on the full time 4WD, I would appreciate it.

HAPPY THANKSGIVING

 

[scottm]

There are lots of debates about full-time 4WD vs AWD vs 4X4, Google it and you'll have plenty to read. Essentially, if you have high and low-range, it's 4WD. If this system is intended to be driven on pavement with all wheels powered, it's full-time 4WD. Plenty of AWD vehicles out there, some are essentially 2WD with the ability to briefly power the other two wheels when the normally powered wheels slip. That's barely AWD, but qualifies. My old VW Quantum synchros and Audi quattros had pneumatic locking center and rear diffs, pretty rugged, but still AWD.

I suspect your mechanics got caught up in the confusing semantics caused by overly zealous marketing at the car companies.

 

[JB.]

If anybody feels like chiming in with some more details on the full time 4WD, I would appreciate it.

Basic 4WD first, then we'll get to the 4runner. Differentials front and rear but runs in 2WD most of the time. A transfer case in between can connect the front and rear differentials by locking the drive shafts coming from each together. Transfer case can also engage some reduction gears for lower gearing. This is called part-time 4WD because it's not meant for full-time use on pavement.

Put a differential in the transfer case so the front and rear drive shafts can rotate at different speeds when the vehicle is turning, and it's now full-time 4WD. Lock the center differential and the vehicle is operating just as the part-time system above.

Your 4runner is like the second system but with a fancy center differential that's more capable than a regular one. This Torsen differential can maintain the full-time operation while utilizing a bit of locking type behaviour for better traction in slippery conditions. It's a purely mechanical, geared differential which means it's very strong and reacts instantly. The one in your 4runner is set up to provide 60 percent torque to the rear, 40 to the front in normal traction conditions, but if one end starts to slip, it can change that 60/40 torque split within a range of 71/29 to 47/53.

When the tech had all the wheels in the air, the Torsen center differential was acting like a regular open differential. The power flowed to the path of least resistance which was, apparently, that one rear wheel. If he would lightly touch the one wheel that had spun, the spin would show up somewhere else, I'm guessing at the other rear wheel but if both were touched then it should go to the front.