4HI Speed

[neversummer]

Hey guys did a search but didnt find what im lookin for.

As the manual reads 4HI can be disengaged at any speed. My question is what is the top speed that you can run in 4HI? Now before everyone gets their panties in a twist...To get around that line of 9 cars going 35 on a little snow in the only passing lane in twenty miles...you may hit 75-80 for a sprint. Should not have any ill affects? Correct me if im wrong.

THX

Mike

 

[jreiter]

Technically speaking, 4HI and 2HI probably have the same speed limit. The only thing that happens to the drivetrain when you switch into 4HI is that the front half-shafts engage, allowing the front wheels to be driven. (That's how it was on the Tacomas, at least, and is probably the same on the 4runner and other Toyotas for the last decade or so.) Toyota probably lists a lower speed limit for 4HI purely on the basis that any situation that needs 4wd is probably not a situation in which you should be going too fast!
:lookout:

When you shift out of 4wd into 2wd, you are simply disconnecting those front half shafts. The front differential is actually still being driven, so no gearing is being engaged or disengaged. That's why you can shift between 2wd and 4wd while moving at a decent speed.

Shifting between 4HI and 4LO, though, requires you to stop since you are shifting the actual transfer case into a different gear. The transfer case has no clutch like a normal transmission, so it needs to be stopped before you can shift it. Just think of it like a 2 speed manual transmission with no clutch. Shifting it while moving will just cause a lot of grinding.

Definitely be careful out there! Try no to go too fast on those snowy roads!

 

[Snooperstyle]

I just went 75 in mine on a packed sand road in 4H. Had the center diff locked because I was in 4H (not FTFWD...mine is a LTD) because I was trying to turn off the TRAC so I could get a little sideways (not at 75) to get more familiar with the tires and the mannerisms of the truck. I didn't want the center diff to put too much power to the front end. Anyways, I was wondering the same thing about higher speeds in 4H, but I always heard it doesn't matter as long as you are on surfaces that are somewhat slippery.

 

[jreiter]

Anyways, I was wondering the same thing about higher speeds in 4H, but I always heard it doesn't matter as long as you are on surfaces that are somewhat slippery.

Yeah, as long as the front and rear differentials can have a bit of slip between them, you're fine. In your case, though, the Limited's all-wheel-drive is fine on dry pavement as long as you don't lock the center diff. If you do lock it, then the same issue applies where you need a bit of a slippery surface, just like with the part-time 4wd vehicles.

 

[1000MPH]

IMO, if you can go 30 on a snowy road you should be in 2wd...unless you're trying to 4 wheel drift in the corners. 4wd is to get you out of trouble not into it.

 

[ct221933]

Hey guys did a search but didnt find what im lookin for.

As the manual reads 4HI can be disengaged at any speed. My question is what is the top speed that you can run in 4HI? Now before everyone gets their panties in a twist...To get around that line of 9 cars going 35 on a little snow in the only passing lane in twenty miles...you may hit 75-80 for a sprint. Should not have any ill affects? Correct me if im wrong.

THX

Mike

Having read the manual from cover to cover and not finding the answers regarding 4HI driving, I decided to call Toyota customer service this morning to clarify. Here are the answers I got from Toyota:

(1) What is the maximum speed to drive in 4HI?
It is ok to drive at the posted speed limit in 4HI (including highway speeds).

(2) Is it ok to steer the vehicle while in 4HI?
It is ok to steer the vehicle.

(3) Is it ok to drive the in 4HI in dry concrete/asphalt?
It is ok, but it is advised to drive in 4Hi in wet or snowy conditions on concrete

I asked if I can be referred to a manual or document, or even emailed the answers. Toyota said no, but the details of my call are logged.

 

[jreiter]

IMO, if you can go 30 on a snowy road you should be in 2wd...unless you're trying to 4 wheel drift in the corners. 4wd is to get you out of trouble not into it.

I think I might disagree with that. I like to use 4wd to keep myself out of trouble in the first place. I could certainly slowly and carefully drive along a snowy road in 2wd and only shift into 4wd when I start slipping and need the front wheels engaged. However, I'd much rather just leave it in 4wd the entire time, just to make it less stressful. I guess I'd rather avoid getting into trouble at all, rather than only relying on 4wd to get me out once I'm in it. The way I see it, 4wd is a great tool for control and safety on roads with bad traction, and it can work very well at preventing trouble in the first place. Why not use it the whole time?

As an example, there have been plenty of times in my home town in the mountains where there was light snow on the highway (prior to it being plowed). I'd shift into 4wd and leave it there while happily driving 30 mph, and I felt I had sufficient traction. The brakes worked, acceleration worked, turning worked. I'd see no reason to drive in 2wd in that circumstance just because I was doing 30 mph. (Unless I intentionally want to slide around a bit!) Granted, I'd never drive 75 mph along a snowy road.

 

[M1911]

IMO, if you can go 30 on a snowy road you should be in 2wd...unless you're trying to 4 wheel drift in the corners. 4wd is to get you out of trouble not into it.

It is best to be in 4WD before you think that you'll need it. Once you need it, if you're not in 4WD you might be stuck too much to get it into 4WD.

 

[neversummer]

I dont know, I have been in WYO for most of my life, and with the traction aids available in the 4runner i feel MUCH safer on an icy snowy highway (at highway speeds) in 2WD. Just for the simple fact that the nannies are toned down a bit in 4WD. Other than needing 4WD traction to pass or accelerate, 2HI is best for icy highway cruising. But just my opinion.

 

[neversummer]

Also thanks for the info guys. Makes me sleep better at night.