Nailing it

Give your axle a birthday – or recommission a spare

Ed Hughes and PC alumnus, Sam Glover, show you how to rebuild your live rear axle at home.

1 Clean the casing

Use a wire brush, screwdriver and scraper together with a degreaser to remove as much dirt and loose rust from the axle as possible. This allows close inspection and stops dirt getting in during repairs.

1 Be prepared!

It’s a good idea to obtain a kit of gaskets, shims, oil seals etc in advance. The job can be then (with luck) be completed in one go. This avoids the possibility of removed parts going missing while stored.

4 Remove plates

To get the halfshafts out of the axle beam, you’ll first need to unbolt a retaining plate that holds the backplate in position and the wheel bearing in the axle. The bearing usually comes out with the shaft.

2 Look for damage

Examine the axle casing for cracks, dents, bends and deep corrosion around mounting brackets, etc. Cracks can occur anywhere, but pay close attention to highly-stressed mountings and welded seams.

2 Remove drums

Take off the brake drums. They may sit on a flat flange on the end of the halfshaft or be held on a taper. Tapered types need a special puller that acts close to the centre of the drum.

5 Withdraw shaft…

TIP

You’ll have to shock the wheel bearing out of the axle casing. Improvise by refitting the drum and its retaining nut very loosely and banging the drum against the nut repeatedly to draw it out.

3 Eye test

Look at the eyes provided for dampers and radius arms to see they’ve not gone oval with wear. If so add some weld and file back to shape, or consider repairing (or replacing) the bracket with fresh metal.

3 Key to success?

A tapered halfshaft will usually have a Woodruff key. Remove it with a pick or (carefully!) with a punch and stow it safely. Note: a tapered joint is never oiled or greased on reassembly – always dry.

6 … and bearing

Our shaft comes out with the inner track and roller bearings still attached and the outer track loose. Standard ball bearings should come out in one piece.

7 Remove bearing

This bearing is mounted on a slight taper, so we dropped it through a vice to shock it off. A shrunk steel ring must have a flat ground on it and then split with a chisel before the bearing can be tapped off.

1 General inspection

We’ll replace the pinion oil seal of the final drive and make a simple inspection of the rest of it. If it looks OK, then it’s best to leave it alone. If it looks OK, but drives noisily, it may need adjustment only.

4 Remove pinion flange

Although many pinions can be simply tapped off their splines, this one required the use of a makeshift puller. The steel section is secured to the flange while the centre bolt is screwed in against the shaft.

8 Extract oil seal

Finally, extract the oil seal from the end of the axle tube using a tyre lever (or a stout screwdriver with the end bent about 30º). Examine the bearing seats (axle and shaft) for signs of spinning and burning.

2 Check wear and adjustment

Gear teeth should be unworn. Expect little or no slop in the small gears of the differential (in the centre). There will be a small backlash (0.010-025mm) when rocking the crownwheel back and forth.

5 Remove pinion oil seal

The oil seal is now accessible. The pinion shaft makes removal awkward, so pierce the seal in several places and lever it forcefully but in stages. This way it will come out intact, rather than tearing into shreds.

9 Shims fitted?

Repeat for the second halfshaft. This axle uses shims to set endfloat of the taper-roller bearings. If it’s never been disturbed, the old shims may do for the new bearings - but you’ll probably need a selection.

3 Remove pinion nut

Remove the pinion nut. You’ll have to jam or clamp the pinion flange to do this. You’ll probably have to start the nut moving by hitting an old T-bar or spanner with a heavy hammer, as it’ll be very tight.

6 Assess drive flange

Look carefully at the pinion drive flange. Make sure the bolt holes are not elongated or cracked and that the area where the oil seal bears is not heavily grooved and scored. Replace it if either is the case.

1 Fit new pinion seal

Either use a large socket or a nylon hammer to tap the new seal into place. Start it off by tapping around it with the hammer so as to seat it evenly – then use the socket or mandrel to drive it home.

4 Fit wheel bearings

Tap new wheel bearings gently into position. Shrunk steel retaining rings will need heating almost red on a hotplate before being dropped quickly over the axle shaft and tapped home – check your manual.

7 Backplate and seals 2 Tighten pinion nut

Tap the drive flange into position and then screw the nut on. Use a new self-locking nut, or a new split pin for a castellated nut. Tighten nut to correct torque – often between 100-200Nm, but see the manual.

5 Insert halfshaft

Insert the halfshaft and tap the outer track of the bearing home in the axle casing. For taper bearings, a shim holds the clamping plate slightly above the track (see next picture) to set the required endfloat.

Fit the brake backplate – here mounted over the top of the bearing clamping plate, but not in all cases. The bearing sits in a space with only grease – don’t over-pack it. It’s separated from the axle oil by the halfshaft seal. This felt-sealed baffle keeps the grease from escaping onto the brake backplate.

Note the teardrop shape – this incorporates an emergency oil drain. Our axle is upside down here…

3 Fit halfshaft oil seals

Using the same method as for the pinion seal, fit the two halfshaft oil seals. Their recessed position makes them a bit more tricky to drive in straight, so take your time and try not to cock or distort them.

6 Taper bearings

The endfloat may be set independently at each halfshaft. If the two shafts effectively touch in the middle, then shims can be placed at either or both sides to set combined endfloat. See your manual.

8 Fit cover plate

If you haven’t already, replace the cover plate (if fitted) with a new gasket and a smear of sealant. If the plate has been overtightened, flatten the strained mating edge or replace the plate.