What did I do? Differential damage? 4 WH test and now yuck sound...

Is this sarcasm?

What happens when you're on rough terrain (sand/mud/snow/etc) while going up or down a mountain for example?

I'm not trying to be a d#$%. It's an honest question. I've never done any serious off roading, but from seeing others do it, are they really shifting back into 2WD every time they come up on a turn, and then switching back into 4WD until the next turn?

ETA: To put it another way - surely if you're driving down switchbacks next to a drop off then damaging your differentials probably isn't your biggest worry, but I would think 4WD Toyotas (and other brands) had to have been engineered with that in mind.

Or in other words, off road trails (whether in sand, mud, snow, gravel, etc) are most likely not going to be perfectly straight roads.

 

Pretty sure he meant on pavement you can run in 4H but should avoid sharp turns

 

Like other wise folks have said, the dealership isn’t your friend, even if ur friend works at the dealership lol. Don’t lie, but don’t tell them everything if you haven’t already over the phone, don’t give them too much info cuz they’ll stick you with it - 100% they’re already going to sell you more than you need. It’s possible it’s no as bad as you fear. I swear if you tell these people you blew your diff, they’ll quote you a diff

 

You’re correct, you can do whatever you want with it off the pavement. I’m sure the post was about street use since that is what the OP was talking about in terms of causing the issue.

I have a 4th Gen and IIRC, their system is different. I have no qualms about driving in 4HI on pavement and have done so many times in the 10 years and 170K miles I’ve had the truck. Not just to do it, but as part of the monthly 10-mile “exercise” recommended to keep the system happy.

 

Well, spoke too soon, still making a decent amount of concerning noise

 

There is a service bulletin for the front diff, you might get lucky. The humming / whirring / vibration you hear at the 35-45mph is the bearing in the drivers side of the front diff. You might get lucky, some people are getting the whole front diff replaced due to this service bulletin. Somebody post the front diff cycling humming TSB please.

 

I suspect if the dealer mechanic cross-threaded the bolts holding the skids on he/she wouldn’t say shit. Take that as you choose.

 

Hey, I think we are all guilty. Some just admit it sooner than others.

Cheers,

Sean

 

That's right, none of that woke 2WD shit

 

IGNORANCE!!!

 

When you put the vehicle in 4WD you are forcing the front wheels to rotate in sync with the rear wheels...they are locked together. When you turn the steering wheel, say in a left turn, the outside (right) wheel has to rotate faster than the inside (left) wheel because it has more ground to cover, but it can't because it is locked to the rears so you are putting binding/stress into your driveline. You must have noticed that the steering was difficult when parallel parking in 4WD on pavement because that's about the worst thing you can do (sharp corner). That's why your owner's manual tells you only to use 4WD on slick surfaces where the front wheels can slip. You still have a lot of traction on rain-covered pavement so it's not a good place to use 4WD.

But the 4Runner driveline is strong. Almost every owner has felt the binding in their steering when they use 4WD when they shouldn't, but I think it's rare for it to cause a problem. I know that even when parking on grass I feel some binding if I turn sharply, so I'll sometimes take it out of 4WD to eliminate the binding but even if I stayed in 4WD I'd be shocked if damage occurred.

So in your case there is no doubt that you did something wrong, but given that there is also a Technical Service Bulletin about defective front differentials there could be some doubt about whether your problem was caused by you or the vehicle. Google "4Runner front differential TSB" to see the TSB.

Regarding what to tell the dealer I agree about being honest. Biggest question in my mind is whether you tell them that you tried 4WD briefly in the rain (in which case most 4R owners would not expect any problem) or whether you also tell them about parallel parking on pavement in 4WD since that might be considered abuse.

 

I know people are mentioning that the front diff might be making the noise, because there is a known issue with all front diff needle bearings. Some/many can make noise in 2wd at around 30 to 45mph. The noise goes away when you shift it into 4wd, in fact, putting it in 4wd is a sure fire way of diagnosing a loud needle bearing. If it goes away, it’s your needle bearing.

That said, I don’t think there is reason to suspect differential damage over other possibilities. Turning sharply in 4wd on a paved surface is also straining the transfer case and driveshafts.

That’s worth keeping in mind when you state your problem at the mechanic. I’d take the approach of stating your problem (it’s making a noise), let them ask you questions, and let them sort through the process of diagnosis. If you give them info that makes them favor an explanation, they may not be as careful looking for the cause, which can lead to replacing expensive parts that don’t fix the problem.

 

Just to follow up, all appears to be good. Dealer saw nothing wrong, said sometimes the 4wd wont disengage all the way, or something like that. Don't necessarily trust that, but for now all seems good. Appreciate all the help.

 

i like to excerise the 4wd once a month for a couple of minutes on a nice straight away. Keep actuators freed up.

 

Wet pavement is not a “low traction” surface. Only use 4wd on snow, ice, sand, dirt, gravel, etc… never on dry pavement or wet pavement. If you need it due to not feeling safe get better tires or trade for a Limited. Look up engineering explained’s video on the different types of 4wd and why these limitations exist

 

Good deal. I assume you’ve tried to engage 4wd since the “incident”?

Regarding the comment that 4wd doesn’t disengage all the away…there is something to that. Here’s a little story…

I have an OR with the shift lever, and I find it communicates exactly what it likes and doesn’t like when being shifted. It does NOT like to be shifted out of 4wd with any tension on the system whatsoever. The lever lets you feel how bad it is because the shift feels gummy, and has way more resistance to moving. And even if you get the lever physically moved to 2wd, the 4wd light will not always turn off, usually not until the binding finds its way out of the system. Let me tell you it feels horrible to shift with any tension in the system…even if it’s just the tension from the suspension being slightly articulated.

On SR5s with the electric shift actuator, you don’t get any of the this feedback to your hand. So you might shift it into 2wd whenever you want, thinking/hoping the system will protect itself and sort itself out. However, I’m willing to bet that the electric actuator is a just a simple dumb electric motor that just throws the shift exactly when you tell it to. It will make an effort to shift, and if can’t, maybe there is a pressure mechanism or timer that will turn off the electric motor and you are simply left with the transfer case in whatever position it was able to get into.

Those bad shifts are not good and are to be avoided!!! My transfer case failed when I felt a gummy shift and the light didn’t go out. That happened going straight, slow, but on a very slightly uneven grass surface. The failure involved the synchro or synchro assembly judging from the part that came out transfer case drain hole, and the brassy sparkles in the oil.



On a more recent trail run, I’ve also been witness to a 3rd gen tacoma wrecking the transfer case on a shift that occurred right before turning right from a trail onto a highway. It lost all drive and was dead in the water on the highway. So we towed it trailside again to do some head scratching and phone-a-friending. We determined that the actuator did not complete the shift stroke, and the shift rod that goes into the TC was physically locked somewhere between 4lo and 4hi. Presumably the actuator could not overpower the binding forces on the shift rod (in the same way I can feel it hard to shift my lever when bound). The shift rod had to be literally hammered into the 4hi position so the owner could at least continue driving it with the actuator removed. The fact it didn’t move freely was later determined to mean something broke inside. Actuator itself was taken apart during trouble shooting…it’s not much to look at besides a cheap motor, plastic gears, clock springs, and contact switches.



Both of these transfer cases were replaced by salvage transfer cases, so unfortunately I can’t give a full post mortem on how they failed, but fail they did!

There is one clear lesson here…avoid shifting the transfer case whenever it might be binding in any fashion. Shift only on flat and level conditions only. So if you ever find yourself turning on dry road surfaces in 4wd…don’t panic shift into 2wd just to try and save it! It’s too late at that point…, just drive straight to get the tension off the driveline, and only then, shift into 2wd. At least that’s the advice I’m following.

 

Actually if you only go straight on dry or wet pavement you are ok. It is turning on dry or wet pavement that is the problem with part time 4WD as the wheels are locked together and can’t turn at different rates as is needed then, unlike when not in 4WD.

 

agreed, straight and no tight turns. I do it once a month for 5+ mins to keep things moving.

 

It’s pretty simple, just try to unload the drive system by letting off the gas or gently applying brake pressure before transitioning one way or the other.

 

Correct, that’s why I suggested to watch the video. Going straight is 100% fine, turning however is just a matter of time before the binding in the transfer case leads to failure. If only 4x4s had some slip in them from the factory with the option to lock it. Of course the limited does, but that would solve a lot of issues for a lot of people.

 

Same here and I do 4LO in my Apt parking lot about 0.1 mile back and forth 2X to exercise it and 4HI for about 10-15 miles as recommended by the manual, engaging and disengaging several times. Mileage lubes transfer case well I think.

 

Not so there is still a differential on the front axle. Parallel parking now, that's really pushing it.

Why in the world would you want to try parallel parking in 4H?

 

The front differential is not the problem! Any small amount of research in this topic and you will see that the binding occurs in the transfer case. When you turn the wheel at all you are changing the rate at which the left from the right wheel moves (hence the open differential in the front and rear) you also are changing the rate of the front wheels from the rear however there is no differential or slippage allowed between the front and rear.

On a low traction surface like snow, ice, sand,etc… this isn’t a problem because the wheels can slip on the surface. On dry and wet pavement however the grip is too high leading to skittering and binding. It is only a matter of time before the transfer case breaks under the strain.

 

This thread reminds me I need to head over to an unpaved area near me to put everything 4wd through the paces...after all the Mother's Day festivities, that is.

To all you 4R moms, BTW, happy Mother's Day!