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Jeep Lock Out Hubs

by Terry L. Howe

This article covers everything you could possibly want to know about hubs (aka lock-outs) and other axle disconnect systems for short wheel base Jeeps. The same principles apply to larger Jeeps as well and at some point this article will be expanded to cover the systems used in the larger Jeeps.

Hub, Brake Hub, and Lock-out

The name hub is a bit confusing because other parts of the axle are called the hub, so to avoid confusion the term lock-out can be used. The confusion comes from the fact that the lock-out bolts onto an outer part of the axle normally called the brake hub. The brake hub has the bearings in it and the lugs go through it to bolt on the wheel.

What a Hub Does

The hub bolts onto the brake hub. Inside the hub is a splined sleeve that moves in and out when the dial is turned. This sleeve slides over the outer part of the axle shaft when it is in and it is away from the axle shaft when it is out. This is the way hubs engage and disengage the front axle.

What the Axle Disconnect System Does

The axle disconnect system used in Wrangler YJs has a vacuum motor that slides a little shift fork. The shift fork rides on a sleeve that ties the two pieces of the inner axle shaft together when it is engaged. The short side shaft spins all the time.

What are Six Bolt Hubs?

The term "six bolt hubs" often cause a bit of confusion since all CJs, YJs, and TJs use wheels with 5 lugs. There are two styles of brake hubs used on CJs between '72-'86. From '72-'80 they used a brake hub (for a 5 lug wheel) that had 6 bolts to hold on the lock-out. From '81-'86 they used a brake hub (for a 5 lug wheel) with 5 bolts to hold on the lock-out. There is a limited selection of 5 bolt lock-outs available and the OEM 5 bolt lock-outs are fairly weak. For this reason, many people will swap in 6 bolt brake hubs and 6 bolt lock-outs on their '81-'86 CJs.

Driven Plates

It wasn't until the 70s when hubs became standard equipment for Jeep CJs, before that they were optional. Most CJs you see will have them installed though. What was used in their place you ask, the answer is driven plates. A driven plate slides over the end of the axle shaft and bolts onto the brake hub, so they are basically a hub that is always on. Driven plates tend to be stronger than hubs, but that takes away from your "weak link". Some people will carry a driven plate in case they break a hub.

CJ-7s built from '76-'79 with the automatic transmission and Quadra-Trac transfer case all came with driven plates. You must convert this transfer case to part time operation before installing hubs.

What Kind of Hub do I Have?

Over the years, CJs have used basically 3 styles of hubs

  1. 10 spline/six bolts for mounting used '71 and prior
  2. 27 spline/six bolts for mounting used '72 - '80
  3. 27 spline/five bolts for mounting used '81-'86
The '87-'95 Wrangler YJ used an automatic vacuum operated axle disconnect system and the newer Wrangler TJ '97+ doesn't use any disconnect system what so ever. There are many advantages to having a Jeep equipped with hubs or some sort of axle disconnect system, as long as the system is reliable.

Can I Put Hubs on my Wrangler?

There are kits being made today to make it possible to install hubs onto a Wrangler. Installing hubs onto the stock axle on a Wrangler is not necessarily a simple operation. Converting a Wrangler to hubs would not necessarily be advantagous. Wranglers use a small 5 on 4.5" wheel bolt pattern (CJs use 5 on 5.5"). The small wheel bolt pattern does not leave much space for a hub and the small hubs tend to break. If you have ever wheeled with someone with a Ford Ranger, you have probably seen a hub break. The Ford ranger uses the 5 on 4.5" wheel bolt pattern and hubs, the hubs break all the time (but they are very easy to replace).

Increased Fuel Economy

One reason to use hubs is to increase the number of miles per gallon/ kilometers per liter. If the the hubs are unlocked, the axle shafts, carrier, and front drive shaft are not spinning. The decrease in spinning parts means the front axle rolls easier and a front axle that rolls easier takes less power to propel. Bearings used in the modern axles that are available in newer Jeeps have very low rolling resistance and the Wrangler TJ does not come with hubs or an axle disconnect system because there is not a significant savings in fuel economy.

Reduced Wear and Tear

Another advantage of hubs is the decreased wear and tear on the front axle. As mentioned previously, the axle shafts, carrier, and front drive shaft do not spin if the hubs are unlocked. This wear and tear is minimal though especially since, if you are not in four wheel drive, these parts will not be spinning under load. For most vehicles, the ring and pinion of the rear axle lasts for the life of a vehicle with no maintenance besides occational gear lube change. Since the ring and pinion of the rear axle spins under load for every mile a vehicle travels, it is likely the ring and pinion in the front axle will survive for the life of a vehicle even if it spin all the time.

In Case of Breakage

One of the best features hubs is they allow you to stop your axle shafts, ring and pinion, and front drive shaft from spinning if you damage something. If you can disconnect these parts you can prevent further damage and it might make an undrivable vehicle drivable.

Weak Link

The hub should be the weak link in your front axle. Hubs are generally less expensive to buy than shafts, ring and pinion, or drive shafts. Hubs are also a lot easier to replace than an axle shaft or the ring and pinion. Spare hubs are also easy to pack. The 5 bolt hubs are a bit too weak, the 6 bolt hubs are a good balance of strength.

Locker Up Front

Hubs can also be handy to have if you have an automatic locker up front. Automatic lockers such as the Detroit "No-Spin" and Lock-Rite locker are on all the time, there is no manual way to turn them off. Sometimes you don't want to have the front lock up such as when driving in snow or loose dirt/sand. Unlocking one or both hubs will make it easier to steer. Some four wheelers even wheel most of the day with only the passenger side dialed in and lock in the drivers side when needed.

When to Lock and Unlock Hubs

People often ask when they should lock in and when they should unlock their hubs. The answer to this is anytime they want to. It is convenient to keep your hubs locked all the time so that you don't need to get out to lock them in and you can shift into four wheel drive on the fly.

Types of Hubs

This is the factory 5 bolt lock-out used from '81-'86. They are built by Warn, but most do not have the Warn logo on them. They are not known for their strength. There are heavier duty 5 bolt lock-outs available if you are reluctant to upgrade to 6 bolt lock-outs.
The Warn preminum hubs are probably the most common hub to find on a Jeep with 6 bolt lock-outs. They are a good, reliable, all around hub.
These Selectro automatic locking hubs are probably the second most common hub to see on Jeeps with 6 bolt lock-outs. They have an "auto" and "lock" postion on the dial.
These hubs are built by Warn and they are common on International Harvester vehicles. The IH ones have a little IH logo on them rather than the Warn logo. They are an auto locking hub with an "auto" and "lock" position on the dial. I've heard IH owners complain about the reliability of these hubs.

Contributors

Thanks to Rick Boiros for the hubs picture and Bill Lally for the spline counts.

Last modified Wednesday, 01-Dec-2010 09:15:12 MST


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