Serious Question: How fast in 4 High?

Ok, I'm board... wife and kids are on vacation while I work my butt off and pay for their life of luxury. Any way, I was reading through the threads, saw a post that was locked and figured it must have gone down hill fast so I'd better check it out.

This thread http://www.tacomaworld.com/forum/2nd-gen-tacomas/101547-super-rain-tires-2.html got locked, but there must be something I'm missing. If I take the paper card insert out of my drivers side visor plastic pocket (that's the official name so back off), there is a message that says...

1. Normal driving on dry, hard-surface roads, use H2 position.
2. H2 to H4: Keep vehicle speed below 60mph

I read that clearly to state when going from H2 to H4, keep your speed below 60mph, which clearly indicates that going 65mph on a rainy highway is perfectly fine in H4.

Am I missing something? Why is this guy getting bashed for using H4 on the highway in the rain?

 

I don't think he got bashed for so much for using H4 in the rain as much as he claims it's perfectly fine to drive 80 mph in a rain storm.

 

OK, I get the hydroplaning reasoning for giving someone a hard time... but if it's raining, you're going the speed limit ~70mph and you hit some oil/water and hydroplane, wouldn't it be better to be in H4 than H2 so that when 2 of your wheels regain traction you will be better off? I mean, the odds are that your front wheels will regain traction before the rear wheels (gravity... mass...) so isn't it better to be in H4 in the rain?

 

No.

If you turn in 4wd and the front wheels have good traction, the front differential will bind up and stop you dead. I did this accidentally in a ski resort parking lot a long time ago when I left in in 4wd upon arrival on a cold, snowy, icy morning, then came back at the end of the day after it got warm, pulled out of my space, and got stuck in a turn (at very low speed). It took a lot of finessing to unbind it and get out of 4wd, even on wet pavement. That was a lesson well learned.

So if you do this at high speed when you need to make an emergency maneuver, even if the pavement is wet, you could lose control of your vehicle and get into a world of hurt pretty quickly. If you have decent tires with good wet traction, they are going to try to give you traction.

If you have to slam on your brakes and the rear end comes around (I'm just not even going to factor in ABS here) and you instinctively turn into the skid, as you should, you would also bind up the front end, and could end up immobilized and sideways in the middle of an interstate in the rain. I wouldn't want to be there...

4WD is just different from AWD, which is designed to be used at higher speeds and normal traction/steering conditions.

Count on good tires and your driving skill in the rain instead.

 

I would NEVER use 4wd on pavement no matter the speed. Only time i'd use 4wd on the road is if the tires arent even touching the asphalt, such as there being a good layer of snow on the ground. Still, 4wd doesnt make you invincible, in fact it can just get you into a more hairy and dangerous situation than proper driving practices and care while using 2wd.

As for speed, I've run 4wd off highway at speeds in excess of 65 mph, but that was on beach/dunes in fairly soft sand where starting off from a stop would just dig the 2 back tires otherwise, and I never clicked it out after getting goin.

 

OK, it's starting to make sense now. This is my first 4x4 and I've never had an AWD yet... (GTR in my future I hope), but I know RWD and rain = danger after having a 400 rwhp sports car in the summer time in FL. I always thought that "IF" I were to hydroplane and the front wheels regained traction (with the rear wheels still 100% out of control) that could spell trouble. I guess the answer is that IT COULD SPELL TROUBLE, but so could a situation as described above.

So... slow down is the best answer... cool.

 

the salesman that walk me through my tacoma when i first got it mentioned to me not to use 4x4 when driving over 15mph, even H4.. i didnt get it why he said that, but he said it would burn/wear out my front axles faster.. anyone can verify this? i know its not for highspeed driving but c'mon H4 should normally take speeds way over 15mph right? lol

 

Salesman usually are clueless in every industry, they just want to make the sale. Sorry to all you sales guys out there...

The 60-65 mph tops in 4h is a pretty good rule. I've driven 60-65 mph for 100s of miles straight on ice/snow covered roads and never had a problem other than losing a couple mpg. I've also just clicked into 4h at 60mph to pass someone or if the surface or the road looks scary and never had a problem. Just remember to click back to 2h when you can and be careful making sharp turns in 4h for the binding.

 

I've used 4H up around 65-70 mph. I agree with the other posters, you should slow down to be safe, but I've used it for reassurance in snow and a brief downpour and/or to pass someone. It's not necessary, but I like the feeling of more control...it doesnt' take much to get the back end a little loose, so being in 4-wheel provides a little more control keeping the truck straight and true.

I would argue to a brief point that 4-wheel can provide a little more safety when hydroplaning. With little to no weight in the back, it is possible that your rear wheels will hydroplane before the front. If you're in 4-wheel, the front drive wheels might continue to drive you straight through the puddle, flood, etc, keeping you in control. However, if your rear begins getting loose, this should be an indicator you're going too fast!

 

i actually drove on 4H for the first time today, turning and backing up is pretty tight and requires more gas, why is that? the wheels seems to stick to the ground causing some noise.. would that cause more wear on the front drivetrain?

 

pavement..

 

Job security for the Toyota Techs. Hopefully they read this and deny your warrenty claim when you break something......

 

Wow... first off 4WD locks the front and rear driveshafts together, so only use when the conditions will allow tires to slip (heavy rain, snow, sand, dirt, mud) and never on dry pavement (unless slowly and driving straight, for experimenting). The front tires will rotate more than the back, as they turn the vehicle. Turning the truck, on dry pavement in 4WD is not easy and that should be a sign something is wrong with what you are doing.

AWD (full time 4WD) has a third, middle differential which allows the front and rear driveshafts to rotate at different speeds, so driving on dry pavement is fine... and makes the vehicle more able to drive fast on mountain roads (see rally racers in their Subaru, Audi Quattro, and other AWD cars).

If you are able to drive over 70 mph, I seriously doubt you need the 4WD. Slower speeds, 4WD will allow you more control in turns and slowing since the tires in the front are locked to the ones in back and you don't have the free spinning like 2WD vehicles have, in front.

The newer Tacomas have VSC & TRAC, and that is great for rainy weather... no more rear end spinning out as you turn from a stop. Before, I would kick in the 4WD to prevent that from happening.

 

x2....If you're interested in some "light" reading, here's some 4-wheel 101: when in 2-wheel drive, when you turn a corner, the inner wheel travels a shorter distance than the outer wheel. This is why we have differentials, it allows each wheel to rotate a different distance or else you'd put strain on the axle. In a standard front-wheel drive vehicle, the back wheels are not connected to each other (i.e. independent rear suspension) and the front wheels are driven by the transaxle (a transaxle is essentially a transmission and a differential combined). Therefore this isn't a problem. However, in a rear-wheel drive vehicle the driveshaft comes from the transmission then goes to the rear differential which drives the wheels and also allows them to turn at different rates (this is why if one wheel is stuck in the mud, the other will continue to spin, unless you have a limited-slip differential).

In a 4-wheel drive vehicle, you also have a front differential. When you're in 2-wheel drive, the front drive shaft that goes to the transfer case is not engaged and can free-wheel. Late model tacomas don't have a locking hub, so I'm not sure if the differential and front drive shaft spin all the time, even in 2-wheel, but I won't get into all of that. When you engage 4-wheel drive, you've now forced all 4 wheels to spin at the same rate. The rear differential handles the different turning rates of the left rear and the right rear wheel, and the front differential handles the front two wheels. However, there is no "differential" that handles the difference between the rear and front wheels. Therefore, the sluggish feel when turning in 4-wheel is called "wrap"...imagine your axles and driveshafts are like rubber bands. They wind up, putting stress on the metal, until you either ease the pressure or the shaft breaks. All-wheel-drive vehicles have a "center differential" with is basically a differential for the center drive shaft allowing the front wheels from turning independently from the rear wheels, eliminating wrap. That's why an AWD vehicle is engaged all the time...kind of "4-wheel drive for idiots".

You don't get wrap on loose ground (i.e. sand, gravel, mud) because the wheels slip on the ground and eliminate any wrap. However, on dry pavement, there is no slip and the driveshaft is forced to wrap like a rubber band. Over time, you'll wear it out and it will break. This is also why you'll feel the truck hop if you try to turn...if the wrap or wind-up is tight enough, it may have enough energy to spring the truck forward and will feel like the truck is hopping.

Long story short....never drive a 4-wheel drive vehicle on hard drive pavement because you'll put strain on your drivetrain that may result in a catastrophic failure. If the truck is sluggish or hopping...stop what you're doing!

 

The Tacomas have essentially 'automatic locking hubs' but it is done by the front differential... each time you go into 4WD the front axle is engaged, when you are in 2WD it is free wheeling the same as locking hubs provide.

 

Thanks, I wasn't sure...so the front axle is spinning all the time, but the front drive shaft is not unless your in 4-wheel?

 

well here i go, bash if you would like,

when i go to the drag strip, i run in 4wd, superweerty runs well over 100 mph in 4wd, i run 96 mph with 33's at the strip, super is like 103-106 i think, he will chime in i bet