Question about old locking front hubs on CJ work?

[Lil Ennis]

What exactly happened when you would have to get out and spin the two front hubs on a CJ for 4wd. WE called them hub lockers where they really a locked front axel? I am not real clear on how FAD works but is FAD what made the front hub lockers obsolete? thanks

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[grimmjeeper]

Basically, FAD (and CAD in the 80s and early 90s XJ) does a similar job that the locking hubs do. But it's not exactly the same.

In the old CJs and trucks, you disconnect the axle shaft from the wheel hub out at the hub. So when you're driving down the road unlocked, the axle shafts don't spin at all.

The new axles are 100% connected all the time out at the hubs (now unit bearings to save cost). So when you're driving down the road, the axle shafts always spin.

The passenger side inner axle shaft is 2 pieces. The axle disconnect just slides a collar to either lock the 2 halves together or let them free spin.

What that does is let the open differential free spin just the axle shafts. The inner passenger side spins "backwards" when you're disconnected, while the outer shaft spins forward. The driveshaft doesn't move while you're disconnected.

 

[cj7ox]

Locking the hubs on old-school 4wd vehicles engages them to the axle shaft. When unlocked, the front hubs spins freely from the axle shaft, reducing the drag of turning all the extra weight of the front drive assembly. With the hubs locked, the axles, differential, and front drive shaft would all be made to spin by the turning of the wheels when in 2wd. This reduces fuel mileage, and saps some power from the engine as it has to work to overcome all of that rotating mass. This has nothing to do with having a "locked" axle, which is actually a locking differential. If you do have a locked differential and not locking hubs, driving can be a little sporty. The FAD on modern Wranglers serves much the same function (though not quite as well) as locking hubs by disconnecting the left and right axle shafts from each other.

 

[SoK66]

Adding that with the FAD the driver side axle shaft and the inner section of the passenger side axle shaft are still connected to the front differential. As the driver side is connected to the driver front unit bearing/hub, as the driver front wheel turns, the driver side axle shaft in turn spins the side gears and spider gears inside the differential. The disconnected passenger inner shaft will spin backwards.

 

[roaniecowpony]

Adding that with the FAD the driver side axle shaft and the inner section of the passenger side axle shaft are still connected to the front differential. As the driver side is connected to the driver front unit bearing/hub, as the driver front wheel turns, the driver side axle shaft in turn spins the side gears and spider gears inside the differential. The disconnected passenger inner shaft will spin backwards.

Yeah, this is not ideal. But it works. The spider gears were never designed to rotate constantly at the speeds seen with this system. They are plain bearing and the gears are straight bevel type, that are as forged (not cut/ground) if I recall correctly. I think that's where a lot of metal debris comes from in these axles.

 

[Lil Ennis]

I understand the CJ way now, its nice and simple. I will be pondering the JL way for awhile.

 

[SoK66]

Will just toss in, the JK in my profile pic is converted to manual locking hubs using an obscure kit by Spyntec (Solid Axle Industries). The reason for the conversion was multi-factored, but was primarily due to front driveline vibration that resisted all fixes. It is based upon the Warn hubs used on CJ/Bronco, with a proprietary spindle & hub that incorporates ABS functionality. Wheel bearings are Bronco spec.

Downsides, must convert to 5x5.5” bolt pattern wheels and 297x (1310) front axle shaft ujoints, that is D30 rather than Rubicon size. I offset this by using CTM solid billet ujoints & chromolly axle shafts. RCV also applies a stronger drive gear for the hubs to fix a chronic weakness with Warn hubs. You also have to have the center hole on any rotor other than 12” CJ milled out to 4.005”.

They work great, on highway they really improve handling and you get a small MPG boost. Downside is all cost, and the only way you can justify the expense, if there is one, you must do the conversion as part if your ini

Positives, improved driving dynamics on Highway, nothing spinning. A small mpg boost. Negatives are all cost, andthe PITA maintenance required. Essentially they are cool but make no economic sense because so much has to be swapped out. Solid never developed them for JL/JT and really doesn’t advertise them for JK any longer.

 

[roaniecowpony]

Will just toss in, the JK in my profile pic is converted to manual locking hubs using an obscure kit by Spyntec (Solid Axle Industries). The reason for the conversion was multi-factored, but was primarily due to front driveline vibration that resisted all fixes. It is based upon the Warn hubs used on CJ/Bronco, with a proprietary spindle & hub that incorporates ABS functionality. Wheel bearings are Bronco spec.

Downsides, must convert to 5x5.5” bolt pattern wheels and 297x (1310) front axle shaft ujoints, that is D30 rather than Rubicon size. I offset this by using CTM solid billet ujoints & chromolly axle shafts. RCV also applies a stronger drive gear for the hubs to fix a chronic weakness with Warn hubs. You also have to have the center hole on any rotor other than 12” CJ milled out to 4.005”.

They work great, on highway they really improve handling and you get a small MPG boost. Downside is all cost, and the only way you can justify the expense, if there is one, you must do the conversion as part if your ini

Positives, improved driving dynamics on Highway, nothing spinning. A small mpg boost. Negatives are all cost, andthe PITA maintenance required. Essentially they are cool but make no economic sense because so much has to be swapped out. Solid never developed them for JL/JT and really doesn’t advertise them for JK any longer.

I went to great length to retain my FAD when I installed 4340 axles (w/1410 U-joints) because I didn't believe my oem pinion-knuckle angle would work out well with my lift.

 

[scootertoo]

Those manual hubs physically connected the front wheels to the axle shafts, letting power from the transfer case reach the tires. Unlocked, the front just freewheeled. FAD does the same thing internally, so no need to get out and turn anything.

If you ever have an overnight sleet and/or ice storm and your ride sits outside and you are getting ready to go and want to have 4WD..............those hubs might be frozen and you just might need to go back in the house and return with a panful of hot water.
Don't ask me how i know that from my 71 Chevy Blazer many many years ago

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