I think this is the right forum, if not ... I am sorry and can someone tell me where to place it.

I have an 03 FX4. How fast can you drive in 4wd low? Question is based on driving in the heavy rain.

Thanks!
Anthony

 

why do u need 4wd low for rain?

 

Do not use 4wd on pavement, even in rain. to much traction and will cause problems in your transfer case. The system is designed to have a bit of slip when you are off road.

If you are off road in 4wd low, just be careful of blowing an engine. It's not the speed, it's the rpms you have to be careful of.

 

The answer to the question is roughly 55-60 mph depending on the options and tire sizes your truck has. However, as mentioned above, completely unnecessary for rain.

-Joe

 

There's almost no reason for the normal person to use 4 low anyway. It's for pulling something hard, not for mud bogging.

Unless you have really big tires, and a wimpy engine.

If you're driving down a muddy dirt road, just leave it in 4 high, and drive like normal. You can go 80 mph and it won't hurt it.

 

I have occasion for using 4 low at least once a month if not more often. Backing a trailer into a tight corner or up-hill, almost got stuck numerous times in my front lawn last weekend backing a heavy trailer through the mud, running in sand or deep snow, DEFINATELY in the mud as long as I can generate the wheel spin needed to clean the tire lugs (and to reduce the strain on the trans)....

And I consider myself 'normal'..... but then again, I live next to a nuclear power plant, so maybe my perception is skewed?

-Joe

 

That was true for the 4x4's of the last couple of generation of 4x4 trucks, but you can run 4hi on pavement and not damage it with the 'new' ones... You don't what to be making lock to lock turns and such obviously, but going straight the TC does not know if you are on pavement or gravel...

I 'exercise' my 4x4 quite often when I'm stuck in bumper to bumper traffic on the hwy... Hell, in Seattle, that's EVERY FREAKING DAY!! So you are only going 25 mph anyway at best!

I don't use 4lo on the hwy obviously, but I'll switch to 4hi just to get the fluid moving in the diff and to keep the solenoid's and vacuum things freed up...

158,000 miles and it's all working fine!

I use 4lo when backing my trailer into tight spots. Especially at home, because it's a tight spot and it's uphill! My trans temp will soar in 2hi and backing the trailer. Tried 4lo and it was so much easier to maneuver and the trans temp doesn't rise at all....

Anyway, my owners manual says not to exceed 45mph in 4lo. I put it in 4lo just to see what it would be like. Going up my steep driveway, it actually shifted into second gear and I was only going 5 mph or less! I drove it down the street once and it was in OD going 25 mph!

Your front diff is an OPEN diff, so one wheel will spin free if it needs to spin faster then the other (ie, turning). If you have an LS rear end, you might get a wheel that 'chirps' in a turn, but the rear axle is a lot stronger then the front, so you should be fine...

Just use common sense and if you hear or feel any kind of binding, then back off and adjust what you are doing....

Mitch

 

In rain put in in 2wd and do a donut But you really shouldn't need 4wd in the rain, just mud, tight spots, snow... weather conditions like that.

 

The only reason you haven't broken anything yet is because it's a ford. Regardless, this is a BAD idea. Your front axle doesn't spin the same speed as your rear axle. That's why your owner's manual says not to operate it on a hard surface. It's because the front set of tires spins faster than the back set. The reason for this is simple. When you make a turn, your front tires have a larger turning radius than your back tires, so they need to be turning faster than the back set. If they were the same, your truck would make very, very wide turns. A CJ-5 is the only vehicle that I know of that the front axle spins at the same rate as the rear axle. And it can get away with it because it's so short.

I would highly recommend that you quit doing that.

It's a good idea to use it regularly. Just be sure that you're on grass, or at least dirt when you do it.

 

No way, Jose. A locked transfer case on pavement will cause driveline bind-up. Sure, the forces won't be as great when driving in a straight line, but the front and rear wheels do not turn exactly the same distances thanks to tire wear, inflation differences, and and simple variations in the rolling circumferences of the tires.

The fluid is moving in the diff and transfer case anytime the truck is moving. In 2wd, the spider gears are turning which will stir up the fluid, and in the t-case, the input shaft turns the positive displacement pump that lubes everything inside it. Good point about exercising the vacuum actuation system for the front axle. The solenoids and Center-Axle disconnect are the components that tend to stick due to lack of use.


JMC and I did the calculation once.... stock 265/70-17 tires, stock gearing, stock red-line for the 5.4 put the vehicle right around 60 mph IIRC. I wouldn't recommend it for highway use, but for short durations (climbing a sand dune for instance) it's not going to hurt anything.


While you are correct about it being an open diff, when you lock the transfer case, the front and rear DRIVESHAFTS cannot turn at different speeds, and that's what causes the driveline bind-up. When cornering, the total distance traveled by the front wheels is greater than the total distance traveled by the rear wheels, and if the transfer case locks the driveshafts together, one cannot turn farther than the other.

-Joe

 

You are right about pulling a trailer, or backing one up a hill. 4low is definately the way to go, but if you're risking bogging down, you need to be in 4 high. You need the extra spinning speed to clean the lugs out.

 

Dito. Except that the front drive shaft is turned faster than the rear axle. It is forced to turn faster by the transfer case.

 

Actually, it's not.... it's a 1:1 ratio front to rear. Assuming the same final drive ratio and tire sizes front and rear, the driveshaft would, in theory, turn the exact same speeds when traveling straight ahead. Lock the t-case, and BOTH shafts spin at EXACTLY the same rate.

But it's a moot point.... 4x4 on dry pavement is a bad idea. 4x4 on wet pavement is questionable at best, but not a good idea in most situations.

-Joe

 

Well if that's the case then the f-150 is different from every truck ever built up to now. I'd check into that, cause i'm almost positive that's wrong. You wouldn't be able to make a turn in 4wd if that was true. The truck would just slide sideways.

Front axles on 4wd always spin faster.

 

That was true for the 97-03, but models prior to 97 and 04 up have nothing turning in front except the wheels. Prior years had the manual or vacuum operated hubs and 04 up has the vacuum operated IWE.