HOW TO OVERHAUL YOUR STEERING BOX

WITH ED HUGHES

STORY PRACTICAL CLASSICS MAG

WEEKEND WORKSHOP

WITH ED HUGHES

4 (HRS) 25 $

REBUILD YOUR WORM-AND-ROLLER STEERING BOX AT HOME

IS THERE PLAY in your steering? Or is it stiff, graunchy or otherwise peculiar? If so, start by checking the steering joints and the balljoints or kingpins.

Then, have a look at the steering idler (on the left chassis rail in the mirror position to the steering box), which may need lubrication and adjustment.

With the steering rods disconnected, it should have no play but present only very slight resistance to turning. If all these seem fine, turn your attention to the steering box.

Start by checking the boxís adjustment. Most have an adjuster screw in the top plate that raises and lowers the drop shaft to alter the mesh of the worm and roller. Others have shims under the top plate that can be removed to serve the same purpose.

The quick method of adjustment is to rock the steering wheel in the straight-ahead position while watching the wheel rims (not tyres) for movement.

Tighten the adjuster until thereís no lost movement.

Be very careful not to overtighten it.

A better method, though, is to disconnect the steering rods from the Pitman arm on the box.

Centre the steering by counting turns of the steering wheel. Now turn the steering wheel 30į and adjust the box until play in the arm is just eliminated. This will give the box a very slight over-tightness at dead centre. Play increases towards full lock at each side, which is designed-in.

Itís vital that the centre position of the steering shaft (and worm gear) corresponds to the straightahead position of the road wheels. If it doesnít, adjust the trackrods equally on each side until it does, then reposition the steering wheel, if necessary.

If adjustment fails to remove play, action is needed. Start by removing the box. This is often a pain, but the pleasure of working on it on a bench makes it worthwhile. If you follow this guide and keep on top of lubrication and adjustment, itís keep on top of lubrication and adjustment, itís unlikely that youíll ever have to do it again.

YOU WILL NEED

Vice, large socket set, breaker bar, Pitman puller, tyre lever, blow torch, heavy hammer, torque wrench, household varnish.

MAINTENANCE

Periodically check the oil level. Fill it just short of the filler hole or to any vent provided (often a slot in the adjusting screw) Ė whichever is the lower.

GET A PULLER

Youíll need a Pitman arm puller to remove the very tight steering arm.

KEEP IT CLEAN

Get the box spotlessly clean with degreaser and a paintbrush before disassembly.

REMOVING THE PITMAN ARM

01

UNSCREW NUT Use a six-point impact socket on a breaker bar to undo the large Pitman arm nut. If you lack a stout vice and workbench, remove the Pitman arm with the steering box still attached to the car.

02

PULL ARM Use a puller to remove the arm from the shaftís tapered splines. Itís likely to be reluctant. Leave a nut on the shaft to prevent distortion.

Tap the arm back and forth to assist its release.

03

REMOVAL TIPS Soak the tapered joint in penetrating lubricant for as long as possible in advance. Use heat, but sparingly Ė it can weaken steering components. Be similarly restrained with the hammer.

DISASSEMBLING THE STEERING BOX

04

REMOVE TOP PLATE Remove the locknut of the adjuster screw, plus any locking tab that may be present.

Remove the top plate retaining bolts.

Screw the adjuster in a few turns and tap the top free of its gasket.

05

RELEASE ADJUSTER Gently tap the bottom of the drop shaft to raise it, then slide the adjuster plate out of the slot.

Some designs have an adjuster that screws directly on to the main shaft.

Unscrew it to separate.

06

REMOVE DROP SHAFT Lift the drop shaft out of the box. You should now see the worm gear of the steering shaft.

It turns on caged ball bearings that run directly on the ends of the worm. Check smoothness of rotation.

07

TAKE OUT WORM Unscrew the end plate retaining the worm. There will be adjusting shims under here Ė donít lose or damage them. Tap the end of the steering shaft to push out the end bearing and release the worm.

08

CATCH BEARINGS Be ready to catch the ball races on each end of the worm.

They should retain their balls unless badly worn. Instead of a shimmed end plate, some boxes have a screw-in end plug with a locking ring.

09

PRY OUT SEALS Pry out the oil seals with a tyre iron, or similar. Drift or press out the remaining (upper) bearing track of the worm if it rotated noisily or if itís rusty, pitted or worn. Otherwise, leave it where it is.

ED SAYS

You can mix-and-match good worms and rollers from scrap boxes with identical innards.

ASSESSING CONDITION

01

WORM AND ROLLER SURFACES Look all around the running surfaces of the worm and roller for excessive wear, especially at the wormís centre. Also look for excessive corrosion and pitting due to debris or manufacturing faults.

02

ROLLER BEARINGS Ensure the roller turns smoothly and freely. Inspect the bearings for corrosion and balls that have split and escaped. Complete replacement roller assemblies are available for some classics.

03

DROP SHAFT Insert the drop shaft back into the box and rock it to check clearance in its bushes. Expect just a little play to allow for expansion and oil space. If the shaft is rusty in the bushing area, itís doomed.

04

BEARING TRACKS Light corrosion of the wormís bearing tracks is not ideal. If you have no other option, clean it with steel wool and fit a new bearing. If the worm rotates freely (it will be noisy). Itíll be OK for a few years.

05

ADJUSTERS Make sure the threads of a screw-type drop shaft adjuster (pictured) are in good condition.

If itís a sliding plate type (see Step 2 of disassembly), ensure the plate has no up/down play in its slot.

06

OTHER STUFF Examine the casing for stress cracks, particularly around mounting holes. Also check the mounting points on the chassis. This photograph shows a screw-type worm end cap for reference.

ASSEMBLING A REBUILD KIT

BUSHES

Donít disturb the drop shaft bushes unless worn-out.

Pressing in thin-walled bushes is tricky and theyíll need reaming afterwards.

BEARINGS

Replace if the old ones are loose, damaged or corroded.

The new bearings will still have to run on the part-worn worm gear, though.

OIL SEALS

Always fit new ones. Theyíll be a standard engineering size Ė shaft diameter x housing diameter x depth (eg, 20 x 45 x 7mm).

PUTTING IT BACK TOGETHER

01

WORM BEARING TRACK If you removed the upper bearing track of the steering worm, begin by drifting it back into place. Ensure itís fully home or it will settle with use and you may need to remove the box again to remedy it.

02

FIT SEALS Drive in the new seals using a socket the right size to bear on the outer edge. Start them off by tapping gently across and around the edge to ensure they go in straight. Oil or grease the rubber lips.

03

INSERT WORM Assemble the worm with its two ball races. Make sure theyíre the right way round. Oil the races and then insert it into the casing. If the shaft splines look likely to damage the oil seals, wrap them in tape.

04

PRESS IN BEARING Drift the lower worm bearing track into place.

The shims will make up the height difference. Fit and tighten the end plate with one less shim to seat the bearing Ė but donít overtighten and distort the plate.

05

FIT END PLATE Remove the plate. Coat the full number of shims in household varnish. Reassemble and tighten. If it has a screw-in end plug, adjust it overtight, back it off to slight preload, then refit any locking device.

06

DROP SHAFT AND TOP PLATE Place the gasket on top of the casing with a little varnish or sealant. Oil the drop shaft and its bushes. Insert the shaft, then introduce the top plate and adjuster.

Donít bolt it down yet.

FINISHING OFF

01 FIT TOP AND PITMAN ARM

Screw the adjuster out until the top plate touches the casing. Tighten the bolts. Coat the shaft splines in copper grease and slide on the Pitman arm.

Note the blind spline Ė itíll only fit in one position.

02 TORQUE AND ADJUST

1 - TORQUE NUT

Fit a new locking washer or Nyloc nut.

Torque up. Itís usually very high (175lb ft, here).

2 - FILL WITH OIL

Refill with oil and check for leaks. Itís usually EP90 gearbox oil Ė but check your carís manual.

3 - ADJUST

Set the worm-to-roller mesh on the bench as detailed in the introduction.