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"Classic Ford", July 15, 2013

How To Replace a diff oil seal

Is your classic Ford’s axle dripping oil all over your driveway or garage floor? Here’s how to stop it.

Some aficionados are emphatic that old Fords leak oil by default. In some models’ cases, this is a fair statement but if any unsightly drips are easy to prevent in the first place then surely spending a few hours and less than £20 is worthwhile?

Although allowing an engine’s oil level to run low might damage it mechanically, the consequences are unlikely to be life-threatening to the driver. Yet, the ramifications of rear axle seizure, during a high-speed trip, might be much more serious. Because many back axle differentials hold less than a litre of lubricant, the level of which is unlikely to be checked as frequently as you find yourself regularly dipping the engine oil, they are, perhaps, the most vulnerable parts of a car to suffer from oil starvation.

Seepages can emerge from several places. Lubricant might find its way past the seals at either end of the driveshafts, which can be identified by oil ‘tracks’ being visible behind the road wheels. If this is the case, immediate action is recommended because it is likely that the brakes would be contaminated. More commonly, leakage is often found at the axle’s nose, ahead of the differential assembly. Luckily, changing the seal is not only quick and easy but it is also extremely cost-effective.

So don’t put your drivetrain at risk, and certainly don’t fork out at the garage — here’s our simple step-by-step guide to take you through the reassuringly simple task of replacing the oil seal on your classic Ford’s differential.

1 Drive the car onto a set of strong ramps, apply the handbrake, engage first or reverse gear, remove the ignition keys, chock the front wheels and place a soft mat beneath the car for you to lie on.

2 If the differential’s nose and lower casing are caked in oil, then the oil seal has failed. This example was so bad that the surrounding area had been sprayed with lubricant, as the car was driven.

3 To avoid dirt and grit from entering the differential and destroying the bearings, coat the area with a suitable degreasing solution prior to rinsing the detritus away, to leave you a clean working zone.

4 Prior to disconnecting the propshaft, use a suitable punch to scribe a reference mark between it and the flange, thus enabling the prop to be refitted in the same position, to reduce the chance of an imbalance occurring.

5 Unscrew the self-locking nuts (plus washers, if fitted), remove the bolts and store them safely. Leave the most accessible one in place until the others have been removed. This will prevent the shaft from dropping onto you.

6 Manoeuvre the rear section of the propeller shaft safely from the working area (there is often no need to remove it completely), ease the retaining nut’s protective cap (if fitted) carefully from its housing, with a flat-bladed screwdriver.

7 As the torque of the retaining nut sets the pinion-bearing preload on some axles, via a collapsible spacer, it is imperative that the nut is not tightened to a higher torque setting upon refitting, so scribe reference marks, as pictured.

8 Only when you’re sure that you have adequate reference points should you unscrew the nut partially. There’s no need to prevent the flange from turning as long as the handbrake is applied.

9 To loosen the flange, fit a puller, keeping the unscrewed nut in place, to stabilise the puller and prevent the flange from slipping from its splines before a further reference point is enscribed.

10 When you’re sure that you can refit the flange to its original position on the splines (use a picture for a reference), remove the nut, washer and flange assembly. Be prepared to catch the ensuing oil.

11 The old oil seal can be levered out with an old screwdriver but be careful not to damage the housing. I refitted the centre nut temporarily to protect the threads. More oil is likely to escape.

12 Take great care not to allow any remnants of either oil or grit to enter the housing. Once the oil flow has ceased, wipe the surrounding area carefully, with a lint-free cloth and ensure that it is clean.

13 On this axle, the oil seal’s lip operates directly on the rear extension of the flange. This was checked for any grooves, which might prevent the new oil seal from sealing correctly, prior to being cleaned gently with fine steel wool.

14 Prior to fitting the replacement oil seal, smear its lip with the suitable grade of extreme-pressure (EP) axle oil. Alternatively, you can soak it in axle oil for 24 hours, prior to starting work. Never fit any seal that appears damaged.

15 Position the new seal squarely into the housing. Do not be tempted to strike it home. Instead, find a socket of an equivalent diameter and tap it gently, with a soft-faced mallet, to drive the seal into place without risking damage.

16 This seal might not be flush with the housing but it is located firmly in place. Prior to refitting the flange to its original position on the splines, lubricate the seal contact area with axle oil.

17 Refit the washer and nut to the flange and, if a collapsible pinion spacer is fitted, don’t tighten the nut beyond your reference points. On other axles, tighten the nut to the specified torque.

18 Replace the propshaft, ensuring that its reference mark aligns with that on the flange. Refit the nuts and bolts and tighten them to the recommended torque figure. Prior to driving the car, replenish the oil level, using the recommended lubricant.



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