What happens when you engage 4wd at speed?

[RiDE]

My neighbor has a week old 4runner and he told my dad thats what he did on the freeway. He heard a loud noise so he's going to the dealer to get it checked.

 

[desy]

A lot recommend you can do 4wd on the fly, but I've always felt why risk it esp when its usually done in the cold when things are least likely engage easily.

 

[PricklyPete]

I would think that in newer vehicles with the 4WD engage being electric..that it would be smart enough to know when it can or when it can not. I've never tried that with my Tacoma...but I'd be surprised to see that occur.

 

[angry hampster]

Toyota was fairly late to adopt shift-on-the-fly technology IIRC. He may have ground up some gears.

 

[IcePickFreak]

Ummm, do cars not come with an owner's manual anymore?

 

[DivideBYZero]

Originally posted by: IcePickFreak
Ummm, do cars not come with an owner's manual anymore?

^

 

[RKS]

I have only used Low 4WD occasionally, never above 15 MPH and never 'on the fly'. I haven't had any issues switching into High 4WD under 40-50 MPH.

 

[StageLeft]

Originally posted by: IcePickFreak
Ummm, do cars not come with an owner's manual anymore?

People read those?

 

[rh71]

1995 Isuzu Rodeo still required a full stop. 1995.5 model did not... they put in an electrical button that allowed shift-on-the-fly under something like 60mph instead of the shift lever / transfer case... I missed that by 3 months. This was 13 years ago... come on now... Toyota.

 

[RiDE]

Well it's still in his garage as I type this and I saw him driving around with it earlier so I guess nothing bad happened.

I'm pretty sure he doesn't read manuals, in fact, I probably know less than 10 people that do. But I'm probably the only one who gets excited over car owner's manuals like it was a porn magazine.

 

[Quiksilver]

My vehicle requires me to engage into park to shift into 4WD, otherwise it will not allow you to.
If your not supposed to but his vehicle doesn't have a way to keep it from happening, I can see the transfer case being messed up.

 

[vshah]

i have an 05 land cruiser prado (sameish car) the owner's manual states that one can engage "High Lock" on the fly, but must be stationary for shifting to "low lock" (which also requires you to depress the clutch pedal)

this makes sense since high lock is simply locking the differential, not switching the transfer case to low range. it does specify that you should be driving in a straight line, and that no wheel slippage should be occurring.

 

[joutlaw]

I think it would depend on the car.

I have a 04 Chevy Z71 and it has a Auto-4WD mode. If it detects slip it will engage 4WD automatically.

You can engage 4-Hi on my truck up to a certain speed... I'm not sure what it is right now... probably under 55mph. I always engage it when it stopped though.

4-Low will not engage unless the truck is stopped and in neutral and possibly in park.

I would hope a Toyota would be able to handle a 4-Hi engagement at speed or at least not allow it if the VSS was registering a speed too high.

 

[HannibalX]

My 2002 Explorer has three settings (push button).

1 - 4x4 auto = standard setting for regular driving. If the rear wheels slip the front wheels engage automatically, even at 70 mph.

2 - 4x4 high = all four wheels are driving the truck all the time with a high range gear.

3 - 4x4 low = all four wheels are driving the truck all the time with a low range gear. You have to be stopped and in neutral with your foot on the brake to engage this setting.

 

[mooseracing]

No matter the vehicle there is additional wear when shifting on the fly. I have rebuilt to many x-fer cases from the past 30yrs of vehicles, the common problem was 4wd not engaging even though it was shifted in. Nearly everyone one of them had a burr on the gear for the 4wd engagment that would allow the mechanism to shift into it. I have had the worst luck with some NP208's....

 

[getbush]

If it was just a single loud bang it's not worth going in for. Shift on the fly still usually works better when stopped, at least from my experience in our '02 Grand Cherokee with selec-trac.

 

[Bignate603]

My cherokee seems to go into 4wd better when rolling slightly but I wouldn't really try it at highway speeds.

 

[marvdmartian]

I've got a 98 Nissan Frontier 4x4, with manual hubs (the auto locking hubs either didn't get offered that year, or didn't get put on it......I bought it used in 99). If we get really bad weather in winter time, I'll drive with the hubs locked (which is a monthly maintenance item anyways) all the time, and have had to throw it into 4H when it got squirrelly in 2H on me (probably my own fault, but what the hell........it's a truck!! :laugh: ). Never had a problem with it while doing that.

I try not to drive in 4H or with the hubs locked on the highway, though, since it does put a lot of strain on the drivetrain. I also try not to drive with the hubs locked for too long, unless it's inclement weather, since it tends to drop my MPG a mile or two per gallon, due to the extra drag of turning the front drivetrain.

However, it being a lower quality Toyota........

 

[kevman]

^ so what is the difference between having hte hubs locked and 4hi ? I thought hubs locked = 4WD engaged ?

 

[Bignate603]

Originally posted by: kevman
^ so what is the difference between having hte hubs locked and 4hi ? I thought hubs locked = 4WD engaged ?

Nope, with the hubs locked it connects the front wheels in to the front differential. The transfer case may or may not actually be putting power through the front drive shaft though so until you engage 4wd the front drive train is just being forced to spin by the wheels being turned.

 

[Raduque]

Originally posted by: RiDE
What happens when you engage 4wd at speed?

You buy a new transfer case.

 

[Mister4x4]

Bignate's correct - locking manual hubs only connects the axle-end of the driveline. Shifting into 4-Hi engages the front axle at the transfer case. In fact, if you have manual locking hubs, and don't go 'wheelin' very often, it's recommended to lock your hubs and drive around for a few miles every so often (usually every 3 months or so - I used to lock 'em when I'd change my oil and unlock them the next day). This circulates the oil in the diff that otherwise might not happen unless you go 'wheelin.' I suppose popping into 4-Hi while leaving the hubs unlocked has the same effect... but I prefer just locking the hubs instead.

Most of the vehicles that have shift-on-the-fly either have live axles (always locked to the diff) or 'auto-locking hubs' (which there are a myriad of ways this is accomplished - vacuum-assist, centrifugal, et al).

I also don't recommend grabbing 4-Hi at highway speeds - the sudden extra traction could possible make things a lot worse. Especially in a higher-profile vehicle prone to roll-over. Rule of thumb: if the roads are bad enough for you to grab 4WD, then you should slow down anyway.

Just my nickel's worth.