MK2 Burman Steering Rack Rocker Arm End Float Adjustment

I am putting my box back together. New seals fitted with help from the forum previously. I amd now adjusting the rocker arm end float. Following the WSM I hand tightened the adjuster till it connected with the rocker shaft. Checked no play, fitted lock nut. There was no play and mechanism felt smooth.

Last step is pop in the spring and then fit the spring retaining bolt. If I tighten the spring retaining bolt down more than shown in the photo then the box starts to get hard to turn until it is rough and starts to stick.

The WSM makes no mention of adjustment of the tension in the spring / not screwing the retaining bolt.

Its just says as a final test something along the lines that’ if the box gets sticky at the center point of travel then undo the lock nut and reset the end float.’

If I do this then I’ll end up introducing some slop that is then relying on the spring to eliminate.

Is this right or should I be adjusting the tension the spring introduces by not screwing down all the way once I am happy with the end float.

You can see below the small gap left between the top of the adjuster and the spring retainer bolt.

Cheers.

Dave

I’m just guessing here, but I wonder if you could shim the bolt so that it’s tight without loosening the end float.

I considered doing that. Using a copper washer to help seal too…but leaves me still wondering if the spring is then doing its job. If the spring pressure is supposed to be adjusted then I will either do that or just set it up with locktite on the spring bolt to hold it in place.

Here is a pic of the adjuster with the spring bolt all the way down- out of the box and upside down. Shows the spring protrudes below the level of the adjuster. It is clear that there would be a lot of pressure from the spring on the rocker arm if the spring bolt is wound down all the way. Since the adjuster is supposed to bottom out against the rocker arm all that you see protruding would be compressed.
It is a really heavy duty spring.

Dave

My thought is if the manufacturer didn’t want the spring to have a job to do i.e. take up some play at the centre point of travel, then they would have eliminated the spring.
Think about where the box spends most of its time, in and around the center of its travel. Where is the wear going to be concentrated?
IMHO if you set the box up and only rely on the adjuster when you go either side of center then the box is going to bind.

My understanding of the reason for this spring is to take up the slight amount of increased play that occurs when the sector shaft rotates away from the neutral centre position when turning.

The follower peg rolls ‘downhill’ slightly, following the radius of the worm as the sector shaft moves away from the centreline position. This would produce a small clearance under the adjuster. The only effect this might have is a light knock or rattle going over bumps, like driveway crossings, due to the sector shaft moving up and down. This increased clearance is only small, so the spring projection only needs to be small.

So the adjustment should be set per the book, i.e. take the adjuster down by hand to zero play in the central position and lock it, check for no binding lock to lock, then install the spring and retaining screw. These two threads usually weep some lubricant over time so it would be better to seal the threads

I know of no other purpose for this. My non-recirculating ball steering boxes on other cars don’t have this spring.

Peter

All the contributions make sense. Still doesn’t really answer my question though :slight_smile: Should the spring pressure be adjusted by not screwing down the retaining bolt all the way.

I have set up the end float with the adjuster. Happy that the box has no play and is smooth. Once the spring is added it starts to bind up. All I can read on these boxes suggests they should be fairly easy to turn on the bench ( but with no end float).

So either I have

A: over tightened the adjuster (even if it feels fine) thereby introducing too much additional pressure on the rocker arm when the spring is introduced.

B: the tension on the spring itself should be set by how far down the retaining bolt is screwed ie just enough to take up the small clearance during travel and perhaps add a little pre-load.

Since there is no mention of B in the WSM I am going to have a go again at A, backing off a little from current position. B does make logical sense though.

Any final thoughts ?

Cheers.

Dave

What I do is tighten the adjuster down to the contact point then back it off a half to one flat, then lock it. The spring and retainer screw is then dropped in and the screw nipped up. It should not be loose or it could come completely loose in service. It will apply a bit of pre-load but this should not introduce any noticeable drag at the wheel when driving.

I’ll be doing my S type box in a month or two and will see if any other hints can be added.

Peter

Thank Peter. Good practical advice :slight_smile: Rules out option B so I will focus on option A following your method.

Dave

So I have got the end float to where I am satisfied with it. I did three things.

  1. There were scour marks where the spring was sitting against the rocker arm. I polished them down to reduce drag

  2. I followed Peter’s advice

  3. And this makes me feel like a real dufus… I filled the box with oil. I had enough oil in to lube on assembly and check for leaks. I had swished it around. Obviously the end float is marginally affected by the presence of oil but more importantly without the worm drive actually sitting in a bath of oil it is never going to get enough lube internally.

The box is smooth across its travel. There is resistance but with the torque delivered by the steering wheel this will ever be noticeable. Feels ‘buttoned’ up.

Thanks for all your help gents. Sometimes it is the stuff that isn’t stated in the manual because it is so obvious that gets the inexperienced :slight_smile:
Dave

Sounds good, Dave. Just another hint. After you’ve run the car’s steering through its paces, such as heavy and tight parking turns, harsh bumps coupled with tight turns like swinging into a driveway, recheck the adjuster screw setting. You may find there is a little more clearance. This is caused by the extra loads experienced in service that settle the various parts into place. This may have been a standard check as part of the first service after purchase.

I agree about the shortcomings in service manuals. Mine mentions nothing about the importance of the bronze bush, the oil seal, or their replacement. Wear here adds to steering wheel play and oil loss. These publications seem to assume the mechanic has prior knowledge and experience with all the details.