Manual Locking Hubs: Locked or Unlocked During Everyday Use

I'm posting this inquiry with the group here because I feel there is a wealth of 4x4 knowledge and experience. I recently received some information from our equipment shop pertaining to our 4x4 fleet of vehicles, this mainly consists of 1/2 ton - 1 ton pickups (2007 and newer). It was a reminder stating: Vehicles equipped with manual locking hubs must be in the "free" or "unlocked" position when not needed for 4x4 operation. Failure to disengage the hubs, especially during highway speeds, can result in component failure and the ability to control the vehicle safely. As the occupant of a 30k vehicle during a front driveshaft failure at 65 MPH, I know first hand that its not fun and can be quite dangerous. Is this information accurate? Is the practice of returning the hubs to "Free/Unlocked" mode a "Must" or just a good practice? As the state engine committee representative I was asked to disseminate this information and want to ensure its accuracy before doing so. I do understand that while the hubs are locked the axles and front driveshaft are being driven by the rotation of the front wheels which could be putting unnecessary wear and tear on front drivetrain components and/or marginally impacting fuel economy. It was previously explained to me that there is no real detriment to the vehicle in leaving them locked even at highway speeds. I have done so many times when 4x4 use will be frequent to save from having to get in and out of the vehicle to lock and unlock hubs. I also understand that most newer vehicles with "on the fly" 4x4 (Jeeps) utilize a form of auto locking or full time locked hubs therefore the front drivetrain components are constantly in motion. Unless I'm going to be going into and out of 4x4 frequently I still utilize the practice of returning the hubs to "Free/Unlocked" before on road use, but don't feel there is any problem leaving them locked all the time. Anyone with information on this please chime in and give me you :twocents:. Any and all information is appreciated. Dynatrac if your listening maybe you could lend a hand with this topic..

I thought one of the benefits is running more caster/ DS angle and not have to worry about failure/vibes.

If this info were true then all 4wd vehicles would have locking hubs would they not? The main reason to unlock your hubs is to save fuel, less parts to move. At least this is my understanding, they are handy if you break an axle or internal diff parts while on the trail as well.

My Experience/Opinion

While saving fuel is a perk and the most common personal reason now days for wanting to unlock them, the main reason is for wear and tear on the drivetrain. Most newer vehicles do not give this option though as parts have gotten better and also have tighter tolerances but if the manufacturer gives this option then i would use it. It'll save money in the long run when it comes to replacing parts and put less strain on the rest of the drivetrain and minimize excessive vibrations (if there is any vibration to begin with).

Edit: ....and obviously there is different perks for this with regards to off road vehicles. Like TrailBear stated above.

CJW said:

While saving fuel is a perk and the most common personal reason now days for wanting to unlock them, the main reason is for wear and tear on the drivetrain. Most newer vehicles do not give this option though as parts have gotten better and also have tighter tolerances but if the manufacturer gives this option then i would use it. It'll save money in the long run when it comes to replacing parts and put less strain on the rest of the drivetrain and minimize excessive vibrations (if there is any vibration to begin with).

Edit: ....and obviously there is different perks for this with regards to off road vehicles. Like TrailBear stated above.

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Yeah this was my thought exactly. I feel its a good habit to get into but isn't essential for everyday use and leaving them locked shouldn't cause catastrophic failure of the front end. Thanks for everyone's input. Anyone else feel free to chime it.

Someone is looking to cover themselves for liability.
I've had a number of 4WDs with free-wheeling hubs, and it's never been an issue to run them in 2WD either locked or unlocked. I've never heard this subject being a concern, and just about every "old school" 4WD in Australia runs free-wheeling hubs.
Unless there is a specific warning from a manufacturer for a particular make or model, then someone is being overly careful.

I would always leave the hubs unlocked when traveling in 2wd. From personal experience, my girlfriend was driving with the hubs locked when the transfer case exploded. The resulting damage included the front drive shaft, the exhaust, the O2 sensors, the wiring to the O2 sensors, the transmission cross member, the transmission, and obviously the transfer case.

If the hubs were not locked, then the front driveshaft wouldn't have been turning to destroy everything it could have hit.

This was an expensive repair that totaled about $9000 after upgrading to an Atlas 4 speed.

keep in mind the mechanical process of hubs versus what we have as "on the fly" of full time engaged hubs differ.

IMO manual hubs should always be unlocked when not in 4x4 or it's dry weather. If you live in winter area and the weather is a mix (dry/snow) then it would be ok to leave them engaged as the weather will provide some slippage even though it's not in 4x4.

The differences in rotation (though slight) can cause damage with no slippage (dry pavement).:twocents:

I had manual hubs on an old F-350. I left them in "free" when not in four wheel drive. This saved on wear and tear and gas. Don't think there was any potential for catastrophic near fatal component failure, just good practice and common sense.


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LeighP said:

Someone is looking to cover themselves for liability.
I've had a number of 4WDs with free-wheeling hubs, and it's never been an issue to run them in 2WD either locked or unlocked. I've never heard this subject being a concern, and just about every "old school" 4WD in Australia runs free-wheeling hubs.
Unless there is a specific warning from a manufacturer for a particular make or model, then someone is being overly careful.

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Yeah I work for the US Government so that is the name of the game. CYA and blame others..haha

safecracker909 said:

I would always leave the hubs unlocked when traveling in 2wd. From personal experience, my girlfriend was driving with the hubs locked when the transfer case exploded. The resulting damage included the front drive shaft, the exhaust, the O2 sensors, the wiring to the O2 sensors, the transmission cross member, the transmission, and obviously the transfer case.

If the hubs were not locked, then the front driveshaft wouldn't have been turning to destroy everything it could have hit.

This was an expensive repair that totaled about $9000 after upgrading to an Atlas 4 speed.

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Yeah I agree with you 100% and I'm sure that would have definitely reduced the amount of damage but I feel this is still a very rare event.

jeeeep said:

keep in mind the mechanical process of hubs versus what we have as "on the fly" of full time engaged hubs differ.

IMO manual hubs should always be unlocked when not in 4x4 or it's dry weather. If you live in winter area and the weather is a mix (dry/snow) then it would be ok to leave them engaged as the weather will provide some slippage even though it's not in 4x4.

The differences in rotation (though slight) can cause damage with no slippage (dry pavement).:twocents:

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Yes driving the front drive train can cause unnecessary wear and tear. Locking the hubs isn't the same as locking the differential and though the wheels are now transferring power to the front half of the drive train the spider gears in the differential allow the wheels to spin at differing speeds so there is no real need for the wheels to slip.



I just don't want misinformation to go out to the end users (Govn't employees scare easy..haha) and make them feel that if they forget to unlock the hubs that its a time bomb that is going to blow up and kill people. Yes its a good habit to get into but if it were imperative there would be a huge warning label on the 4wd shift lever stating to not move the vehicle in 2wd with the hubs locked. I don't know I may be totally wrong...haha.

jesse0920 said:

Yeah I agree with you 100% and I'm sure that would have definitely reduced the amount of damage but I feel this is still a very rare event.

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Maybe rare but it happens quite a bit. Just talk with Advanced Adaptors for a while and you'll realize that it can happen to anyone.

If my Jk had freewheeling hubs I'd have them out when in two wheel drive in the hope that It might help with the fuel mileage lol.
Obviously if your doing more highway driving than off-road it's got to be saving you on wear and tear and a little on gas consumption if you disconnect them.
If your transfer case or driveshaft fails on the highway in two wheel drive with the hubs in then I think it was always going to shit itself anyway and probably off-road and in a far less convenient place.

safecracker909 said:

Maybe rare but it happens quite a bit. Just talk with Advanced Adaptors for a while and you'll realize that it can happen to anyone.

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Yeah as I previously mentioned it has happened to me. Fortunately it was on the axle side of the front drive shaft. It was on a 30k lb. 2001 International 4800 4x4 fire engine with full time hubs. There was the case of the stock drive shaft failing and it caused an engine to go over the side of the freeway. International came out with a retro fitted drive shaft which has two double cardin joints. One at the T-Case and one at the axle. They had an anticipated life expectancy of 50K miles (We learned this after ours failed at 55K miles). While traveling on the freeway at 65 MPH the center ball of the axle side CV joint seized and it let go. It actually sheared the 1.5" Pinion shaft clean off. After one complete revolution it came to a halt rendering no further damage. Had it been the T-case side I could only image what the damage would have been. In addition to the sheared of pinion we got away with a torn open oil filter (Cal-Trans doesn't like when you dump 7 Gallons of oil on a main thoroughfare..), a smashed exhaust and a bent transmission fitting.

hydrohut said:

If my Jk had freewheeling hubs I'd have them out when in two wheel drive in the hope that It might help with the fuel mileage lol.
Obviously if your doing more highway driving than off-road it's got to be saving you on wear and tear and a little on gas consumption if you disconnect them.
If your transfer case or driveshaft fails on the highway in two wheel drive with the hubs in then I think it was always going to shit itself anyway and probably off-road and in a far less convenient place.

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Yeah I don't know what I'd prefer more, freeway speeds or middle of nowhere at probably a much lower speed. I guess its pick your poison..haha