The wheel hubs of the vintage Land-Rover have long posed challenges as regards the effective retention of lubricating oil. Even the factory as much as admitted this fact when years ago they issued a service bulletin directing technicians to replace the 90-weight oil with wheel bearing grease. Given that so many Land-Rovers suffer difficulties in this area, it will undoubtedly prove useful to take a close look at this common problem.
To begin with, it should be observed that the factory, as usual, got it right the first time, incorporating the finest lubrication strategy into their original design. Extreme pressure liquid lubricant (EP90) is the superlative system for assuring the longevity of wheel bearings on vehicles used in the adverse conditions of punishing off-raod operation. Lubricant of this sort, by its very nature, continually cleanses the wheel bearings, whereas wheel bearing grease simply retains debris and contaminants and moves them repeatedly over close-tolerance bearing races and rollers, thus assuring the virtual impossibility that dirt can be detected or removed. The gravitational settling out of debris is simply infeasible. "Ninety weight" [EP90], on the other hand, readily yields evidence of contamination when examined, warning servicing personnel immediately of any foreign debris. It also changes color to various shades of light brown when contaminated by water. Particulates can readily be detected manually or visually, swept with a magnet, or strained to determine the presence of material potentially damaging to the bearings. It is also self-draining and tends to carry off a greater percentage of contaminants when drained. For these reasons it is superior to grease, and, in my estimation, should be used wherever possible.
However, some human beings favour the ever-tantalising, simplistic short cut, and resort to wheel bearing grease. It goes without saying that save in the most extreme of circumstances it does not leak; hence its great popularity. There is, however, another way. Consider the following: When diagnosing leaks in the area of the wheel hub, either front or rear, two presenting symptoms typically come to the attention of our service department: 1. oil leaking onto the road wheel, visible from outside the vehicle, and: 2. oil contaminating the brake drum and shoes. Rarely does lubricating oil find its way to the outside of the backing plate of the brake drum, except in small telltale quantity at the bottom of the backing plate.
Let us, therefore, divide the problem into two parts. Oil leaking to the outside of the wheels is typically either or the other of two problems. One is that the felt-rubber seal [and hence the hub cap] is leaking, the other is that the driving member bolts are loose. Considering the first problem, the felt-rubber seal, let us look first at why it is leaking. Typically leaks occur because the felt-rubber seal is very old, compressed or hard [rarely the root cause], or secondarily because the half shaft [axle] has been allowed to loosen in the driving member. This is often caused because the castellated nut on the end of the half shaft "becomes loose" by virtue of wear of the mating parts: the end of the half shaft and/or the driving member itself. Secured by a cotter pin, the castellated nut cannot actually rotate loose, but instead, not keeping it snug over long miles and/or years radically accelerates the rate at which the male and female splines of the hub can work against each other, causing excessive friction and wear of the mating parts. Half-shaft and driving member splines can actually wear against each other to the point that the splines will eventually wear entirely off. Integral to this process: the felt-rubber seal will be degraded mechanically to the point of leaking.
For these reasons it
is probably the better part of wisdom to disassemble
the half-shaft/driving member about once every
ten-to-fifteen thousand miles to inspect, clean and
reassemble the parts in question. At the same
interval it is always wise to inspect the half-shaft
splines, at both the inner and outer ends, for
possible signs of wear or impending failure.
It is always good drill to
replace the felt-rubber seal, re-tighten the
castellated nut, install a new o-ring under the hub
cap, and possibly also seal the hub cap with R.T.V.
Silicone sealant. Hub caps which are badly distorted
should be replaced, because if they have become
stretched they may not stay in place, and will almost
certainly leak.
Another cause of leaking wheel hubs stems from the six drivng member securing bolts working loose which allows the driving member to rotate slightly each time the Land-Rover is accelerated or decelerated. This can happen for one of several reasons. One is simply that the lock washers have lost their spring tension and allowed the bolts to work loose. Another is that the bolts have become stretched. Yet another is that the splines have become so worn that shock is imparted to the driving member every time power is applied or withdrawn to the drive line, thus forcing the driving members loose prematurely. Actually, excessive wear anywhere in the drive line is potentially problematic to associated parts within the drive line. This condition causes many half-shafts to fail prematurely, as well. These problems rarely appeared with Land-Rovers twenty or thirty years ago, when the hubs had never been stripped down, or had perhaps seen only one service cycle, but it is much more prevalent today in Land-Rovers with higher accumulated miles. Whatever the cause, let us look at some practical remedies.
First, obviously, to diagnose potential faults arising in the hubs, a full strip-down is called for. Begin by removing the hub caps. These can be tenacious in the best of circumstances. I typically use a brake adjusting spoon or "heel bar", [frequently two are required, placed opposite each other] but any type of strong prying device will eventually overcome the tenacious grip of the most obstinate of caps, and obstinate is the definitive term!! Use the surrounding driving member bolts for fulcrums. Next remove the cotter pin from the nut at the end of the half shaft. Do NOT at this point loosen the castellated nut! Instead, use the nut as a diagnostic tool by turning it clockwise, counting the "flats" carefully to ascertain the extent of wear or looseness. The thread count is 16-to the inch, so each flat, then, represents one sixth of that amount, or .267 inches of wear. While the precise amount is perhaps not critically important, when observed over time it becomes a useful relative unit of measure to track the degree of wear.
Now remove the castellated nut and withdraw the driving member itself. Do not try to coax it with a hammer, but use instead a stout pry bar, using any of the surrounding five wheel studs [preferably with nut replaced on the stud to protect the threads] for a fulcrum. Then remove the half-shaft. If it is stubborn, the inner splines may be twisted in the differential. Having withdrawn the driving member, return it to the outer end of the half-shaft. Place the half shaft securely in a vise and attempt to rotate the driving member on the shaft. No discernible wear or play should be detectable, either radially or laterally. Remember that any appreciable wear in the drive line potentially imparts shock to the balance of the drive line and accelerates deterioration of associated componentry. Crystallization of the steel is very common in half-shaft breakage. In sub-critical vehicle usage, wear of the splines may simply be noted for interest, but in Land-Rovers which are used in demanding and/or critical situations, such defects should be corrected to forestall catastrophic consequences. Genuine Land-Rover half shafts, typically the best available, are none too good themselves, and non-genuine shafts can break within a astoundingly short period of use.
I recall the case of a business colleague who drove his Land-Rover in extreme conditions with a weak half-shaft. The so-named half-shaft snapped in a moment of exceptional difficulty, turning the land-Rover sideways to the slope, causing it to roll to a punishing near-death.
Back to the subject at hand. If wear is detected in the splined interface between the half-shaft and driving member it should be borne in mind that each one will cause its counterpart to wear more aggressively, and also to impart potentially troublesome shock to other more expensive components such as the spider gears in the differential, and even the shafts and gears of the transmission. Accelerated wear begets accelerated wear. [And premature breakage]. For these reasons, and others, it is worthwhile bearing these effects in mind when considering the possible replacement of the worn components.
Another reason for leakage at the hubs may be caused by stretched driving member bolts (Part number 251-323). It is interesting to note that when factory-fresh Genuine Land-Rover driving member bolts are torqued to factory specifications, I have seen such bolts to stretch on first installation. The shop manual calls for 30-38 foot-pounds of torque, but I prefer to tighten them by feel, by hand. These bolts are of the British Standard variety [BSF], so use a 5/16 BSF ring spanner [box-end wrench, for you Yanks]. If no BS spanners or sockets are available, a 19/32" fractional will do. If over-tightened, the bolts can snap off in the hub, but they are typically prone to stretching first. In other words the metallurgy is not all that it might be. Cheaper non-Genuine bolts can be even worse!
To inspect the driving member bolts for damage, first clean them in solvent......each and every one......and then dry them off with a shop rag. Now look carefully along the full length of the threads, noting particularly the point at which the threads meet the non-threaded shoulder of the bolt. Observe very carefully the spacing of the threads to see if any are differently spaced, one to the next. This is the point at which stretching always occurs. Stretching can also be felt by running the fingers up and down the length of the bolt: a narrower cross section will be felt at the point where the threaded portion of the bolt transitions to the plain shank. If stretching is suspected the bolts should be replaced, as a limited amount of stretch is possible before breakage occurs. Lock washers should also be inspected for sharpness and spring tension and replaced if questionable. They, of course, prevent the bolts from rotating loose, at least theoretically, but if worn or tired they cannot do the job intended. Do pay attention to the smallest detail; terein may lurk the dread Achilles heel.!
Now, what of the sealing, or mating, surfaces of the wheel-bearing hub and driving member? Many do-it-yourselfers, and a shameful number of "professional" mechanics use a hammer to remove stubborn driving members from the hub, with the regrettable consequence that the hub or the driving member, or both, become distorted, and hence unable to seal oil as originally designed. How to inspect for this injury? First, clean the suspected culprit[s] in cleaning solvent, and dry well. Now inspect the inner machined surface of the driving member, as well as the periphery, for dimples, swelling or bruises which might have been imparted by careless, heavy hammer blows. The surface of the closely-machined face of the driving member will evidence upset, swelling or distortion of the steel, which stands proud of the surrounding material. While this swelling can be removed by machining, it is probably better to move the displaced material back to its intended location with judicious hammer blows. For the uninitiated this should be attempted only gently at first, using the smooth flat face of a suitable hammer. Practice on a piece of scrap wherever possible. Once the majority of the damaged material has been restored to its rightful place, clamp the driving member, inner face upwards, into the soft jaws of a sturdy vise. If your tool box is bereft of one, purchase a top quality U.S. mill bastard file. Using this file, carefully dress down the face of the driving member until it is entirely flat once again. A high-quality, straight, new file will also serve as a reliable, if crude, straightedge. It is characteristic of those unfamiliar with this procedure to remove rather too much material, or not to retain the flat, so it would again constitute time well spent to practice this somewhat delicate operation on a piece of discarded material, so as to make ones' first errors on a non-critical piece. Gently file the entire face of the driving member until it all shines like silver. Constrain the file to very flat, even strokes. Remove any material begrudgingly, but bring the face slowly and carefully to a consistent overall brightness, removing only enough metal to achieve this desired look. Do not remove metal from the inner distance ring of the driving member, as it constitutes an important part of the sealing mechanism. To stay clear of this eventuality, place only the unmilled side of the file against this surface; this is precisely the reason a mill file has been called for.
Back in the days when small Ferrari components were largely hand finished, Enzo Farrari supplied his factory apprentices with a sparkling new, virgin vise at the outset of their internship programme. If they allowed the file to slip off the work and damage the vise just once, they were immediately let go from the works!
Now turn to the wheel hub itself. Has it been similarly damaged by wanton hammer blows, or the careless hand of the clumsy and irreverent? If so, as before, move material back to its place of origin wherever possible, with carefully placed hammer blows. Should the finished face of the hub still prove uneven, apply the same treatment with the mill file until the entire mating surface of the hub is bright silver. Now try the mating surfaces to one another, either clamping them in a vise or utilizing at least three bolts to secure the matng faces snugly together. If a misfit is suspected, use a feeler gauge to check for a poor interface. A discrepancy of only a thousandth or two can easily cause the hub to leak, so the offending member must be dressed down to assure a successful restoration. If a feeler gauge is unavailable, machinists' bluing applied to one surface of the mating pair will surely reveal the necessary information to make the appropriate adjustments. All these efforts, of course, are indicated only when both male and female splines are found worthy at the outset.
The hubs should by this time be ready for reassembly. The factory originally stipulated HYLOMAR brand gasket cement in this as well as many other applications. This product was originally formulated by Rolls Royce, Ltd., and it is a product eminently worthy of the good name of the firm. It is, in the world of gasket sealants, without equal, much like the Rolls itself, and, of course, like Land-Rover! One of the crowning virtues of HYLOMAR is that components thereby sealed can be field-stripped numerous times with loss of neither gasket nor sealant, and thus returned to service repeatedly without incident. HYLOMAR is the sealant of choice with racing and aviation technicians. It was not originally intended for use in joints where no gasket was fitted, but so brilliant is its formula that it will also serve in this application in a pinch.
When reinstalling the half-shafts it is not a bad idea to use them as diagnostic tools to check the differential for possible excessive wear. Simply reintroduce the half shafts to the axle and bolt one driving member up to the hub with two bolts only. Then rotate the opposite driving member/half-axle by hand, listening and feeling for any sounds or lumpy feel which the differential might make. Using the longer half shaft in the shorter side of the axle for better feel. If anything but a silky smooth feel is detected it is probably a good idea to remove the differential for inspection. If the lube oil is o be drained from the axle it is a good idea to catch the oil in a squeaky-clean PYREX glass bowl, being careful, of course, of the dangers of hot oil! Allow the oil to settle for a brief time and hold the bowl up high so as to view the bottom. In this way any steel debris which has settled will be readily visible. An overnight's wait may prove even more revealing, but if time is of the essence, then draw a magnet through the drainings to see if any metallic debris is present. It is all too common that the axle case is not at all, or is insufficiently, cleaned after the breakup of a half-shaft. This, of course, is guaranteed to lead to grossly accelerated wear of the differential gears and bearings. For those unfamiliar to British Northwest's parts offerings, we supply magnetic drain plugs for all oil cavities of the vintage Land-Rover, including the overdrive. In these times when replacement spares for the Land-Rover are becoming more scarce, this can prove both a diagnostic and an economic benefit.