It is not uncommon to find questions on the various on-line
forums asking about the benefits of a Warn hub conversion. It is certainly
a valid question since the cost of the conversion is not trivial. Here are
my thoughts on the various benefits (or lack there of) that you will see.
Mileage - Sorry, you are not going to get better gas mileage because of your conversion. Logic says that if you don't have to spin the front axle shafts, differential, and front drive shaft, you should be able to increase your gas mileage. I agree that logically this is correct, but in reality, you are pushing a vehicle shaped like poorly designed aerodynamic brick through the air at 65 MPH. Your vehicle has a flat vertical grill and a nearly vertical windshield. Any potential gas mileage improvement is negated by the shape of the TJ and the wind drag it creates. I personally saw zero change in my mileage. You could do much better in the gas mileage department by not accelerating so fast or shifting at a lower engine RPM.
Maintenance - The factory unit bearings, commonly called hubs, on the TJ are not serviceable. When they go bad, you simply replace them with a new one. The TJ has been on the market long enough that folks are seeing hub failures as a maintenance replacement expense. I'm not saying they will shortly fail again after you replace one, its just that many folks with some higher mileage or hard vehicle use (rocks, mud, etc.) are seeing it come up. The price of a new unit bearing varies just like most other replacement part and depends on where you shop, etc. $150~$175 each is probably about average. Dealerships are higher priced while a discount parts store is usually the cheapest. Most folks are getting reasonable life from the factory unit bearings. I honestly don't know how the after market units are doing. Regardless, replacing a pair of them will kill one or two of the anticipated mods you were looking to do next month.
On the flip side of the coin, the replacement price for the bearings in the hub conversion are quite reasonable. The Timken bearings that come in the kit are excellent quality. As I write this, I'm going on year 3 for my hub kit. I'm still running the original set of bearings. Each year, I pull my hubs and hand pack the bearings. This gives me a chance to ensure that all is well inside that easy to ignore hub. I do sacrifice two seals while performing this annual maintenance but I see it as no different than the routine maintenance of the fluids in the tranny, t-case, or differentials.....even though it was not bad, new fluid is added and everything buttoned up until an inspection is needed. When I do finally get around to replacing the Timken bearings, I'll spend about $20 price for a bearing (each side requires two). That is a significant savings over a single unit bearing replacement, let alone two.
Since we are commenting on maintenance, the Warn hubs provide you with another benefit, that being greatly reduced maintenance for the front drive shaft. The double cardan joint (also called the CV joint) in the front drive shaft is well known for acquiring a problem that is commonly known as "angry sparrows". The term comes from the chirping noise you hear when the centering ball in the double cardan joint gets a little dry (low on grease)....it sounds like a couple of angry sparrows going after each other. It is usually heard at low speeds and is sometimes temperature sensitive. Taking the drive shaft out and removing all of the u-joints so that they can either be re-greased or replaced with greasable u-joints is the most common cure. Of course, without the Warn hubs, your drive shaft is always spinning, even in 2WD going down the freeway. With the Warn hubs, your drive shaft only rotates when you have the hubs locked and that would normally be when you are in 4WD on the trail (or perhaps bad snowy weather on the highway).
Survivability - Maybe I should call this a durability or strength improvement. The hub conversion comes with new outer stub shafts (the small shaft that is fastened through the hub and connects to the axle shaft u-joint). These stub shafts are chromoly and are a good step up from the factory stub shaft. Warn also offers chromoly inner shafts and these are not provided as part of the kit. In my opinion, it is worth the extra expense to include the beefed up inner shafts.
The reason that most stock shafts fail is not due to the u-joint breaking. The broken u-joint is normally the victim and not the cause. As you stress your STOCK axle shafts during normal use, the non-hardened yoke ears (where the u-joint caps are pressed in) begin to slowly distort. As this distortion increases, the caps begin to loosen. You may have heard someone comment about their u-joint caps "spinning" in the yoke ears. People often mark the caps so they can more easily determine when the cap has started to spin.....and knowing this, they can prevent this kind of failure on the trail (assuming they take the necessary steps to replace the axle shaft(s)).
Anyway, back to the STOCK shafts.....we've been routinely stressing them on the trail and now the caps are getting a little bit loose in the yoke ears. The clips that hold the u-joint caps in place can only withstand so much when the cap is rotating and flexing back and forth and when the clip lets go on an already loosened cap, the cap gets spit out of the yoke ear. When this happens, the trunion slams against the yoke ear. The u-joint can break at this point and the yoke ear often times breaks off as well. Even if it does not break, the yoke ear will be so badly distorted from the severe impact that it will not be reusable.....but remember that it was already getting distorted which was why the cap got spit out anyway. So....you now must replace the damaged shaft, the u-joint, and perhaps the shaft that was on the other 1/2 of the u-joint. If that shaft survived, it can probably become a trail spare (very used but good enough to get you off the trail and back home).
So what do the Warn shafts get us? The heat treated chromoly shafts have hardened yokes. This means that the stress we've been talking about does not distort the yoke ears like it does on the stock shafts. Also, the Warn shaft yokes are relieved so that we can use full circle clips to better retain the caps. In addition to that, Warn machines their yoke ears to a tighter tolerance which means they will retain the caps more tightly than the stock shafts. Yes, that also means that installing the u-joints into the Warn shafts is more of a job because of these tighter tolerances. But the result is an axle shaft that is beefier than the stock shafts. It also means that you may very well break a u-joint and your yoke ears/shafts will survive the episode.
Trip Home - If you don't trailer your TJ to the trail head, it means you have to drive your rig home (like me) once you finish the trail and put some air back into your tires. What happens if you smack your front drive shaft on the trail and end up with a good sized dent in it...or worse yet, bend it? Yep, you will quickly find it unbalanced once you get your rig up to speed. The vibes can be minor or major....it depends on how bad the damage was. With the hub conversion, you would not even realize there were any vibes since you would have the hubs locked out (in the free wheel position) and your front drive shaft would not be turning.
I've had some folks tell me that when this happens, they just unbolt the drive shaft at the front pinion and tie it up out of the way.....so no vibes on the way home. Of course, they still have to do something with it once they get home. This happened to me some time back (pre-Warn hub conversion) and resulted in my spending $100 to have my front drive shaft re-tubed and balanced. The vibrations at highway speed were not so bad that it could not be driven but bad enough that I did not want to let this go unattended and then see those things that fail from drive shaft vibes like a pinion bearing, leaking seal, etc. If I had the Warn hub conversion back then, I would have skipped the drive shaft repair. The slow speeds I do on the trail would not have been an issue for a slightly dented/unbalanced front drive shaft. It would not be spinning fast enough to cause an issue.
Collateral Damage - The failure of one component causes damage to other components, resulting in a much larger repair bill than what the initially failed items costs to replace. This happened to my buddy just this past weekend....and I'll include some pictures since I helped him repair the damage and snapped a few while we did the work.
The scenario that caused him so much grief.....it was the last obstacle on the trail....trying to get over a ledge.....he hears something bang. Once off the obstacle, a check shows no broken u-joints, other parts, etc. The vehicle drives OK, or at least it seems to, so he airs up the tires and heads for home (about an 80 mile trip)....just like me, he does not trailer his rig.
Once home, he notices a leaking front axle tube (driver's side)....not good. To make a long story short, he broke a Superior inner axle shaft on the driver's side. The u-joint/yoke ears were fine....the shaft twisted off at the splines at the differential. Here are a couple of pics.
Here is one very broken Superior alloy axle shaft. It
carries a 2 year warrantee and so my buddy will be getting this replaced for
free (not sure if he has to pay shipping or not).
Here is the carrier, with the bearing still pressed onto it, and the broken shaft still in it. The bearing was wasted as you can clearly see. The broken shaft also chewed up the carrier (where the bearing presses on) making its replacement necessary as well.
This is where the axle shaft seal would go (right where the tube enters the housing). Aside from the metal ring, that was all we found of the seal (and hence, the leaking diff fluid from the axle tube). As you can see, the end of the broken axle shaft did a pretty good number on this part too. The rough edges were taken down with some emery paper and the outer surface of the new seal was coated with RTV in hopes that it would properly seal against the axle tube.
The pinion shaft was removed and the pinion bearings cleaned and flushed of the metal shavings. It is hoped that these will be OK but that will only be determined after some miles have been put on the rebuilt housing.
We could detect no visible damage to the ring and pinion gears (no big chunks went through them).
When all was said and done, the following items were replaced: axle shaft (warrantee replacement), two carrier bearings, pinion seal, inner shaft seal, and a carrier. The LockRight auto-locker was removed from the damaged carrier, cleaned, and reinstalled in the replacement carrier.
Since a new carrier was installed, the gears had to be setup. My buddy was quite fortunate in that he and I supplied the labor for this front housing rebuild. Most of you probably already know what the expense is for setting up gears. A good friend assisted with the gear backlash, etc. so he was fortunate there as well.
Could all of this been avoided if he had a Warn hub conversion.....more than likely yes. My buddy would have locked out the hubs when he aired up for the drive home. So instead of the axle shaft grinding away on the carrier for those 80 miles, it would have sat motionless during the ride home. Once we had it on the lift and pulled it down, we would have found a broken axle shaft and maybe a damaged inner shaft seal....or maybe the seal would have been OK. The rest of the components should have been OK and certainly no gear setup would have been required.
So add all of those parts up, toss in the typical $300 labor charge for a gear setup, and then see how much closer you just got to the cost of a Warn hub conversion. And don't forget, this is just one of the benefits of the hub kit.
Trail fix - On a Dana 30 front axle, people that knowingly invest in a Warn hub conversion for the right reasons also realize that they are stacking the deck in their favor when it comes to an easier trail fix. Granted, nothing is bullet proof and there are almost no guarantees in life, but as I said, stacking the deck in your favor can be a good thing when you are doing a trail repair.
Some folks add one more item to the hub conversion project, a
pair of super strength u-joints, like those available from
CTM Racing Products. A pair of
these u-joints, when combined with a set of Warn alloy inner and outer shafts,
will usually make the Warn hublock the "fusable link" in the front axle.
Here is the hublock mounted and ready to go. The only thing left at this point is to slip the wheel into place and tighten the 5 lug nuts. So....how much easier could a trail fix be? We stack the deck in favor of the hublock blowing out....and if it does, we simply pull the tire, slide the hublock off of the wheel studs, slide the new one on, and remount the tire. Takes about 5 minutes (without impact tools). Warn offers hub fuses in their Premium locking hubs (5 x 5.5" version) but these are not available for the smaller hub conversion kit. So....we build the heck out of the rest of the axle components and then hope the hublock blows first.
Well, that is about most of my comments as to the benefits of running the Warn hub conversion. As I said earlier, nothing is guaranteed and nothing is bullet proof. But that is why we still take spares to the trails. It is my intention to do repairs in the convenience of my garage/drive way and wheel while I am on the trail. Reduced maintenance costs (expensive unit bearings) and the ability to tear down and inspect as necessary also sits a lot better with my method of wrenching and routine maintenance.
What ever you decide on, I wish you the best.
....and remember to TREADLightly!
4x4 Off-Road Homestead Firearms RC Flying