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Dec 28, 2009, 10:02pm

DAF CLUB OF AMERICA :: Tech Toolbox :: Suspension Tech :: Steering Rack Service

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Topic: Steering Rack Service (Read 42 times)

DAF66USA
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DAF-LOVE

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Location: Southern CALIFORNIA

Steering Rack Service
« Thread Started on May 15, 2009, 5:29pm »

In terms of steering and suspension we identified two problems with Betty the Daf. The rear shocks were, frankly, shocking and the steering had excessive play at the wheel and a nasty "clonk" sound sometimes.

The shocks were replaced with a second hand set from Holland but the steering needed a little more effort. There are nylon bushes in the steering rack that disintegrate over time. The top one was completely gone so there was no option but to replace them. They are available from Holland at about £20 a set, but it seemed more fun to make some up.

First, the rack had to be removed. Not a bad job on one of these - it comes out with the track rods attached by undoing a total of 6 bolts and two balljoints.
[image]

The first thing once it was out is to mark the inner balljoints to ensure that the trackrods go back on the right sides and the right way round. In this case, the Nearside Inner joint is marked with N and I.
[image]

After a light cleanup, the play in the top of the pinion shaft can be seen in the following two photos - note the difference in the gap on the left side of the shaft!
[image]

The retaining plate bolts for the pinion are wirelocked but whoever did this one didn't have much idea - if you look carefully, you'll see that the wire over the top of the left bolt won't stop it turning anti-clockwise (undoing) a little. Once that happens, the right hand bolt can also turn, which will give slack in the wire for them to both turn a little more. They could only undo about 1/2 turn, but this plate holds an adjustment in place and even that much loosening could be enough to lose steering completely. We'll come back to how to do it properly later on!

[image]

Once the wirelocking and end plate are removed, the pinion can be pushed from the other side and the retaining plate lifted out. This has a simple keyhole slot and, once it's removed, the pinion can be withdrawn.

[image]

To do this, you have to turn the pinion carrier ("cage") anticlockwise, which increases the clearance between the pinion and the rack teeth. This is the adjustment which is held in place by the wirelocked bolts - if the cage turns the pinion can become disengaged and turning the steering wheel will do nothing!
[image]

The rack can then be taken apart and inspected / cleaned
[image]

Although the main point of this job is to replace the worn bushes, cleaning and a full inspection makes sense. The end of the rack body has a grease seal which consists of two leather rings and a rubber O ring, held in place by a pressed in steel ring. To remove this ring, a screwdriver can be used to tap the edge up at one point, then gently lever around its rim until it comes out
[image]

These parts should really be replaced as a matter of course, as with all seals, but sourcing replacements is a problem and, provided the sealing components are still flexible and not showing deterioration, it's not essential. The rack is lubricated with grease rather than oil and it's vented elsewhere, so there's no danger of pressure building. In this case, the seals were all OK so they were cleaned up and re-used.
[image]

The metal parts are unlikely to wear but should be thoroughly cleaned and examined. The bushes are another matter - one had disintegrated completely, filling the cage with bits of nylon, and the other was starting to split. These have to be replaced!
[image]

The bushes for this rack are still available, but need to be imported from Holland. So the decision was made to turn a set up. This posed a small problem that we don't have any decent materials suppliers around here, so where to get the required nylon? The answer came from a local general hardware store - 10mm thick nylon kitchen chopping boards.

The bush dimensions are 23.2mm outside diameter, 17.75mm internal diameter and 14mm overall length. Using 10mm thick material therefore required making four bushes, two for each end, with one 10mm and one 4mm.

First they were cut out very roughly using an electric jigsaw.
[image]

The four blanks were then centre drilled at 6mm, fitted with a bolt as an arbor, and mounted in my trusty model lathe. Turning plastic like this is nice because you can take fast, deep, cuts with an acceptable finish. Even on a model / watchmakers lathe taking 2mm a pass isn't a problem, so the bushes shape up nice and quickly!
[image]

Once the outers are sized, time to remount and work on the bores. For these, I drilled to 12mm and then turned out using a hand graver to size. This allows better control, especially with a soft material, and makes it easier to ensure the hole is centred properly - important because there will be two bushes at each end. If they don't line up properly then only one will be doing any work! Once finished, the bushes can be fitted to the rack cage.
[image]

Once everything is clean and inspected, the rack is ready to go back together

Having slid the rack back into the housing, a good quantity of grease is applied to the inside of the housing and the rack - particularly the teeth. This is best done with the rack inserted because if you apply the grease first, the end seals will wipe most of it off!
[image]

The pinion is also greased well ready for fitting. Having applied the grease, the rack is withdrawn enough to allow the cage to be fitted. The cage is then turned to it's "maximum clearance" position and the pinion slid into place. The pinion retainer is then refitted.
[image]

With the cage still at its maximum clearance, slide the rack into the housing until it measures 252mm from the centre of the first balljoint hole to the centre of the pinion shaft. With the rack in this position, the flange that connects the pinion to the steering column needs to be parallel with the rack body. If it isn't, then the steering wheel "straight ahead" position will be wrong.

Once everything is right, turn the cage clockwise so that the pinion engages the rack and refit the cover plate, leaving the bolts a sort of loose finger tightness. The cover should be filled with grease to lubricate the end of the pinion

[image]

The free play in the rack is now adjusted by turning the pinion cage until there is just perceptible backlash in the pinion at all points from "lock to lock". The manual states 1.5 degrees of angular play at the pinion shaft, which equates to about 0.2 inches (5mm) at the wheel rim. Too much play will lead to play in the steering, not enough will lead to rapid wear of the rack and pinion.

When the play is right, torque tighten the bolts to 22 Lb/Ft and re-lock with wire. Note the style of locking - if either bolt tries to loosen, it will be trying to tightening the opposite bolt. This is the correct way to do it!
[image]

Job done, rack ready to refit!

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THE BEAR
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The DAF Doctor

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Re: Steering Rack Service
« Reply #1 on May 15, 2009, 6:43pm »

Yes...Joe did an awesome job of documenting his steering rack rebuild.

His DAF site is starting to look good too...that is where all the tech stuff he has done is located.

John

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