So what happens if I drive in 4wd on pavent?

[DesertFJ40]

Hi, good day/evening

As the title states. I left my transfer case in the 4wd "high" position and drove it for about a mile on pavement. Front hubs were unlocked during the drive and I realized my mistake and put my 4wd knob back into the "off" position. I didn't notice any binding. Thankfully there were only a couple of turns and the rest of the drive was straight for that mile.

Obviously running in this manner for extended periods of time will result in damage to the drivetrain, but I'm just curious to know if there's anything in the short term? Has anyone had first hand experience of something going "boom"?



Does the transfer case do much if it's thrown into 4wd and the front hubs are unlocked?

I once read someone on ih8mud say you can do this and drive in off road conditions, but only in short burst, as it can provide too much torque on the rear drive shaft and cause damage. It was labeled as "2wd low"


Thanks for the answers and your time. The Fj40 is still running fine and just shrugged off it's owners dumb mistake for the time being.

 

[Living in the Past]

Should be fine if the front hubs were unlocked.

 

[micruz60]

No harm, no foul. Front driveshaft is spinning freely after you went back to 2wd?

What year is your 40?

 

[suzuguru]

Absolutely nothing wrong with what you did. As long as you keep it under 45 or so, it's good to do that once every month or 2 just to keep everything lubed up good. (assuming you don't use the 4wd often)

 

[4x4veteran]

Running some risk of breaking the splines on the hubs.
I am sure you would have heard something.

 

[flx]

If you had the hub locked in 4wd position, don't worry you would have noticed very quickly on road x)

 

[B y r o n]

If I'm off-base I'm sure someone will correct me.

Open differential in front, hubs locked or not (think drive plates which came from the factory) is not a problem running in 4WD on pavement. No different than AWD vehicles that do it every day. Gas mileage will suffer but that is about it. If you have a locker in the front then you'll feel the problem whenever you try and go anywhere other than dead straight.

As mentioned above, if you haven't run in 4WD in a while it is good to engage and run for a few miles to circulate the fluid in the front end.

 

[flx]

AWD vehicles have a differential (or something playing this role) in the center.

A part-time 4WD vehicle like the FJ40 has no diff in the center, so when 4wd is engaged it means both the front and the rear will spin at the same speed.
When cornering, yes both front and rear differential will adapt the speed between right and left wheels, but when cornering your front and rear axle are also traveling a different distance. The rear wheels don't follow the exact path of the front ones, they tend to slightly cut the corner. So in 4WD mode it will force on the transfer box and the vehicle will tend to not want to turn (on pavement), steering wheel will feel harder to turn (particularly if no PS).

 

[bikersmurf]

It is recommended to lock in the freewheel hubs for a few miles each month to keep things lubed up.

Engagement into H4 while they are locked should only be done on slippery surfaces… but now and then you may have good traction between slippery surfaces. If you have good traction things will bind up (or get loaded up), and it won’t hurt anything if it’s relatively momentarily. You’ll find that you won’t be able to shift out of 4wd till you’ve driven straight for a while or relieved the loading some other way.

I agree with others that having the front shaft spinning H4 won’t harm anything, and should even be done regularly for a short distance to circulate the lubricants.

With the hubs engaged it will also easily shift on the fly between H4 & H2… or L4 & L2 (if you’ve done that mod.

Never shift from L to H when moving. Unless you know exactly what you’re doing it’ll harm things. If you have a tach and are an expert in driving a 15 speed non-synchronized rig then you MAY be the exception… otherwise you’ll blow up your transfer case if you shift while moving at speed.

It can be done, but my advice is don’t.

 

[POPO AGIE]

My 1978 was driven on I-80 in 4WD at the speed limit at the time by the ex wife to work about 30 miles, after I had left in 4Hi because it has snowed. She called me from work asking why it was louder than normal. It was all stock with open differentials and dealer installed Warn hubs. No damage was done.

I rebuilt the transmission and transfer case last year with 103K miles and overall everything looked good except for wear on the splines of the output shaft.
I have removed both differentials this year, they're only needed cleaning and the front was cleaned and the backlash adjusted. The gears all looked good and did not need to replace anything, other than installing lockers. When it was my daily driver from fall through spring my hubs were always locked because of the ever changing road conditions in WY. I would be on the highway watching for slick spots and shifting in and out of 4Hi and 2Hi.

I heard of an old timer that had a Willeys Jeep that was always driven in 4WD until the day he died.

 

[suzuguru]

While open-knuckle systems are arguably stronger, closed-knuckle systems are far more forgiving when it comes to driving with 4wd engaged. This is especially true when driving on dry pavement, or while turning. My Samurai's, and my Tacoma's have no trouble whatsoever driving around town on dry pavement in 4wd high. I don't do that, and I don't recommend it, but I generally drive them at least a mile with 4-high engaged about every 1-3 months. The samurai's have manual locking hubs, so I just leave them unlocked. The Tacoma's have permanently locked hubs, so the wheels are also being pulled by virtue of placing the t-case in 4-high.

All that being said, there is absolutely nothing wrong with driving on dry pavement in 4wd high or low. One must simply be mindful of what you are doing. Driving in a straight line would be a perfect world scenario. However, a few moderate turns would be fine. Even a 90 degree turn is okay, assuming you make your speed appropriate for this application. I wouldn't recommend doing this often, as stated previously, it's not meant for that, and it certainly puts more stress on all components involved. However, occasionally it is necessary to facilitate the movement of lubrication in the system. In the case of lockers, it is quite different. My Samurai's all had Lock-Right's in front and rear. They still didn't have an issue on dry pavement. However, you would certainly hear the locker 'ratcheting' when you were in a slow-speed tight turn. However, unlocking the hubs, obviously, takes the front locker out of the equation. Open-knucle front ends with lockers are absolutely horrible on hard surfaces while turning. It puts a tremendous amount of strain on the axle components. The vehicle will hesitate to move forward and actually lurch when pressure drops due to CV joint position. This is definitely not recommended. Sorry to write a book, but this is one of those things that easiest said in person, rather than typing.

 

[POPO AGIE]

While open-knuckle systems are arguably stronger, closed-knuckle systems are far more forgiving when it comes to driving with 4wd engaged. This is especially true when driving on dry pavement, or while turning. My Samurai's, and my Tacoma's have no trouble whatsoever driving around town on dry pavement in 4wd high. I don't do that, and I don't recommend it, but I generally drive them at least a mile with 4-high engaged about every 1-3 months. The samurai's have manual locking hubs, so I just leave them unlocked. The Tacoma's have permanently locked hubs, so the wheels are also being pulled by virtue of placing the t-case in 4-high.

All that being said, there is absolutely nothing wrong with driving on dry pavement in 4wd high or low. One must simply be mindful of what you are doing. Driving in a straight line would be a perfect world scenario. However, a few moderate turns would be fine. Even a 90 degree turn is okay, assuming you make your speed appropriate for this application. I wouldn't recommend doing this often, as stated previously, it's not meant for that, and it certainly puts more stress on all components involved. However, occasionally it is necessary to facilitate the movement of lubrication in the system. In the case of lockers, it is quite different. My Samurai's all had Lock-Right's in front and rear. They still didn't have an issue on dry pavement. However, you would certainly hear the locker 'ratcheting' when you were in a slow-speed tight turn. However, unlocking the hubs, obviously, takes the front locker out of the equation. Open-knucle front ends with lockers are absolutely horrible on hard surfaces while turning. It puts a tremendous amount of strain on the axle components. The vehicle will hesitate to move forward and actually lurch when pressure drops due to CV joint position. This is definitely not recommended. Sorry to write a book, but this is one of those things that easiest said in person, rather than typing.

I completely agree, not driving on drive pavement in 4Hi and the instructions are clearly laid out on the instruction plate on the glove box and in the owner's manual. I don't intentually drive on hard, dry pavement in 4 wheel drive unless the conditions make it prudent like driving in Wyoming in the winter driving the Rocky Mountain States is different then most states. Our highways in Wyoming are snow pack or black ice and most of state does not salt as other states do. When I see a slick spot coming up I get off of the throttle and shift the transfer case and try not to be under power when I get to the ice or snow pack when the traction conditions change.

I just came back from Jackson Hole over a pass that gets up to 10000 feet with my Ram 3500 and used 4Hi when it was prudent along with my exhaust brake and manually shifted the automatic transmission. Yes, there were a few times when the conditions did improve I forgot to shift back into 2Hi. That truck or the 1500 Ram reacts the same in 4Hi in a tight turn, they don't like it even going very slow. I pay close attention to the feedback from the truck that I am driving at the time I have also been driving 4 wheel drives in all kinds of condition since the late 70s. My FJ40 has always been very forgiving to my driving habits and did not crow hop in 4 wheel drive because of the open differentials. The 71 Bronco was not one of Ford"is better ideas. You had to back up to put it in 2Hi and then unlock the hubs and would not go where my Datsun 1600 would because the 302 did not have any low end and in 4Lo it would not stay on the ground so that the tires would hook up, but never found out how fast it would go in I-80.

When my build is complete I will have to change the way I drive my FJ40 because of both axles having lockers and different gears in the transmission and transfer case. The transfer case has a 3:1 low range so I will not be able to shift to low range on the fly like I could with the 4 speed and transfer case which had a 1.9:1 low range and could choose a gear the transmission that was appropriate for low range while moving. For example, if I was in 1st gear and wanted to shift to 4Lo on the fly I would switch to 3rd and then shift to low range.

 

[Brian/99uzj100]

It is recommended to lock in the freewheel hubs for a few miles each month to keep things lubed up.

Engagement into H4 while they are locked should only be done on slippery surfaces… but now and then you may have good traction between slippery surfaces. If you have good traction things will bind up (or get loaded up), and it won’t hurt anything if it’s relatively momentarily. You’ll find that you won’t be able to shift out of 4wd till you’ve driven straight for a while or relieved the loading some other way.

I agree with others that having the front shaft spinning H4 won’t harm anything, and should even be done regularly for a short distance to circulate the lubricants.

With the hubs engaged it will also easily shift on the fly between H4 & H2… or L4 & L2 (if you’ve done that mod.

Never shift from L to H when moving. Unless you know exactly what you’re doing it’ll harm things. If you have a tach and are an expert in driving a 15 speed non-synchronized rig then you MAY be the exception… otherwise you’ll blow up your transfer case if you shift while moving at speed.

It can be done, but my advice is don’t.

THIS ^^^^^

From the owners manual:

 

[rkymtnflyfisher]

I routinely drive 45-55 mph on snow covered roads in 4 HI, other than a few extra vibrations I haven't noticed anything wrong. Lay off in the corners and pay a little extra attention to the rig and how it's reacting.

 

[JohnnyC]

“What happens if I drive in 4wd on pavent?”

You go forward or reverse depending on what gear your in



Pavent in Latin is “they feed”

If your running over people feeding that’s just wrong … I highly recommend not doing that

​

Sorry @DesertFJ40 couldn't resist … I tried

 

[ToyotaMatt]

Hi, good day/evening

As the title states. I left my transfer case in the 4wd "high" position and drove it for about a mile on pavement. Front hubs were unlocked during the drive and I realized my mistake and put my 4wd knob back into the "off" position. I didn't notice any binding. Thankfully there were only a couple of turns and the rest of the drive was straight for that mile.

Obviously running in this manner for extended periods of time will result in damage to the drivetrain, but I'm just curious to know if there's anything in the short term? Has anyone had first hand experience of something going "boom"?



Does the transfer case do much if it's thrown into 4wd and the front hubs are unlocked?

I once read someone on ih8mud say you can do this and drive in off road conditions, but only in short burst, as it can provide too much torque on the rear drive shaft and cause damage. It was labeled as "2wd low"


Thanks for the answers and your time. The Fj40 is still running fine and just shrugged off it's owners dumb mistake for the time being.

this WILL eventually happen , so DON'T do it ..........

 

[POPO AGIE]

I routinely drive 45-55 mph on snow covered roads in 4 HI, other than a few extra vibrations I haven't noticed anything wrong. Lay off in the corners and pay a little extra attention to the rig and how it's reacting.

You know what it is like to drive in The Rocky Mountains in the winter. I had to learn on slick roads in a short wheel base with a narrow track is not your friend on snow pack and ice. Stay off the brakes and compression brake as much as possible. Use the brakes and you don't know where, when or how you will end, I rolled my FJ40 in a blizzard on the way to work. The conditions were so bad that the interstate was closed and had to take the frontage road to the power plant. Everything from a Ford High Boy and up were on the sides or their tops that night and I did not slow down. CJ5 were the same way I would rather be in my Ram 3500 crew cab it is heavy and very stable and use my exhaust brake and transmission with the 4 wheel drive but I really miss driving my FJ40 in any condition.

 

[rkymtnflyfisher]

Ram 3500 crew cab it is heavy and very stable and use my exhaust brake and transmission with the 4 wheel drive but I really miss driving my FJ40 in any condition.

Same here, the ole diesel dually is a little more predictable on slick roads!

 

[suzuguru]

Over the years, I've had the opportunity to drive several vehicles in snowy and icy conditions. My Jeeps have always done very well, but I've been most surprised by my Tacoma's with the BFG KO2's. We've had some pretty extreme conditions here over the last 10-15 years, and I've yet to find a hill I couldn't go up or down in the old Yota. During the most extreme conditions, I used to do a little circuit locally and see if anyone needed to be pulled up a hill or out of a ditch. I even pulled a semi out of a ditch one year. The driver was dumbfounded. (and very appreciative)

 

[POPO AGIE]

Same here, the ole diesel dually is a little more predictable on slick roads!

I got rid of the dually for a single rear wheel when we sold the 5th wheel. I was using it for work and it was too stiff and the rear tires would wear out too fast and visibility was terrible. I had it in El Sagundo, CA and I would stop at intersections even when I did not have a stop sign visibility was so bad before moving into the intersection.