Amazon: Knock from pitman arm

[JDW3696]

Took it for a drive and the steering is definitely heavier and tighter but not too heavy in my opinion. No knock. I loosened it off a tiny bit as I have read about the dangers of over tightening but I've obviously loosened it too much as the knock returned. I'll try somewhere in between tomorrow. Its pretty slim margins. At least I've narrowed the knock down.

[JDW3696]

No leak and flexibility joint tight.

[JDW3696]

Decided to start again after the advice on here and watching the Amazon Cars video on setting it up. The long and short of it was that the adjustment screw was massively over tightened. I tightened the screw and nut up until there was near enough an instant response on the pitman arm when moving the lower steering shaft. The adjustment is nowhere near as tight as it was and no knock. Going off for a drive to see what it's like. Fingers crossed the adjustment screw being as tight as it was hasn't damaged the box internally. Aside from the advice that it should be tightened just enough until the pitman arm reacts are there any other pointers to indicate a correctly adjusted steering box? Many thanks
Joe

[Derek UK]

Instant response from the Pitman arm isn't a requirement. As I said, it's normal to have quite a bit of play at the steering wheel. Don't worry about that. It's a characteristic of this type of box. It's not rack and pinion! With jack stands under the front suspension, check the feel at the steering wheel as you turn it back and forth across the central position. If you feel ANY stiffness at the centre, loosen the screw a small fraction and retest. The screw has a very coarse thread so the adjustment is very sensitive. It is also vital that the Pitman arm is on the spline in the correct position. Clean off the arm and shaft and check that the the 2 stamped marks align. If someone has had the arm off it may have gone back on incorrectly. Adjustment has to be done with the arm on correctly and pointing straight ahead. The adjustment point or potential stiff spot will be in the wrong position if it's wrong and steering will feel different just off of centre. Car should steer hands off on a good flat road. Also check the toe in if it doesn't. The wheel can be be straightened later if needed. Although the steering can feel a bit tough when manoeuvering it should be light not much above walking speed. Tyre pressures about 32 psi. When all is correct it can even feel a bit too light at full motorway speeds. Adjustment is a learning curve but it's worth getting it right.

[JDW3696]

Okay. Few more things to check. Thankyou for that. I've adjusted it a few times today and I think I've actually got it about right but I'm going to carry out some further checks you mentioned. Thanks Derek.
Definitely alot better than it was. It returns to centre nicely after a turn which I believe doesn't happen if it is too tight. Steering feels pretty good now but I'll check the lines match up.

[simonvolvo]

Originally Posted by JDW3696

Decided to start again after the advice on here and watching the Amazon Cars video on setting it up. The long and short of it was that the adjustment screw was massively over tightened. I tightened the screw and nut up until there was near enough an instant response on the pitman arm when moving the lower steering shaft. The adjustment is nowhere near as tight as it was and no knock. Going off for a drive to see what it's like. Fingers crossed the adjustment screw being as tight as it was hasn't damaged the box internally. Aside from the advice that it should be tightened just enough until the pitman arm reacts are there any other pointers to indicate a correctly adjusted steering box? Many thanks
Joe

It helps to think of the pitman arm shaft as hanging from the lid of the steering box (via the adjusting screw). It should be the adjusting screw that holds the pitman arm shaft up. Nothing else. Certainly not pressure of the “roller” on the “worm”.

In this sense I find the terminology “tightening / loosening” misleading. I suppose it boils down to the same thing, but it would be much better, I think, to refer to “lowering / raising” the pitman arm shaft.

Turning the adjusting screw “in” (clockwise when viewed from above) lowers the pitman arm shaft, bringing the “roller” closer to the worm. Likewise, turning the adjusting screw “out” raises the pitman arm shaft, increasing the separation between the “roller” and the worm.

[142 Guy]

Originally Posted by simonvolvo

It helps to think of the pitman arm shaft as hanging from the lid of the steering box (via the adjusting screw). It should be the adjusting screw that holds the pitman arm shaft up. Nothing else. Certainly not pressure of the “roller” on the “worm”.

In this sense I find the terminology “tightening / loosening” misleading. I suppose it boils down to the same thing, but it would be much better, I think, to refer to “lowering / raising” the pitman arm shaft.

Turning the adjusting screw “in” (clockwise when viewed from above) lowers the pitman arm shaft, bringing the “roller” closer to the worm. Likewise, turning the adjusting screw “out” raises the pitman arm shaft, increasing the separation between the “roller” and the worm.

Simonvolvo has provided a more accurate description of what the adjustment screw is doing.

If you look at the parts diagram the adjustment screw is 'up-side down'. The head of the screw sits inside a recess in the top of the pitman shaft and is retained in that recess by a circlip and adjusting washer. When you rotate the adjustment screw CCW the screw pulls the whole pitman shaft (and its roller) up and CW pushes the pitman shaft down. This moves the horizontal center line of the roller up or down relative to the horizontal center line of the worm gear.

I haven't pulled apart a box to measure the geometries; but, I expect that the 'normal' position of the CL of the roller is slightly above the CL of the worm. Adjusting the Pitman shaft up will inherently increase the worm - roller 'tooth' clearance leading to more lost steering movement. Adjusting the Pitman arm down reduces that clearance and reduces lost motion; but, I expect that the geometries are such that you can lower the pitman shaft enough that it will solidly jam the roller 'teeth' into the cam 'teeth' when the clearance becomes zero rendering the box effectively locked up. As you lower the pitman shaft the tooth clearance is reduced minimizing lost motion; but, the reduced tooth clearance increases friction (and wear) between the worm and roller teeth. Also, if you adjust the screw CW enough you also get increased friction from the screw head pushing down on the pitman shaft.

In my non exhaustive searching for vintage steering box details, I was not able to find a spec for the limits on up - down free play of the pitman shaft when installed in the box. Volvo does put a limit on the axial movement of the adjusting screw that is trapped in the top of the pitman arm by the circlip. For the Amazon, Volvo limits the axial movement of the screw to 0.002". My knee jerk reaction is that if you are getting up-down movement of the pitman shaft as you rotate the steering (leading to knocking) of more than 0.002" you may have a wear issue on the adjustment screw head or the recess in the top of the pitman shaft. Volvo's fix for this is to fit a thicker washer under the retaining circlip to limit up-down (axial) movement of the screw relative to the pitman shaft.

As an observation, oil needs to be able to work its way into the recess on the top of the pitman shaft to lubricate the interface between the adjusting screw head and the pitman shaft. No oil in there leads to metal on metal contact. It is not a high movement area; but, no lubrication will increase the potential for wear. Those advocating for lubricants that are more viscous than the recommended 90 gear oil may be contributing to increased wear on the adjustment screw / pitman shaft interface if the increased viscosity reduces the lubricant that is able to makes its way into the recess.

[Derek UK]

Volvo show their method for adjustment in the Green Book manual. They adjust on the bench using a spring balance to measure the friction needed to turn the shaft. That assumes a box with no wear. Does mean you can ignore that as very few will be unworn. As a rough check you can count he threads showing above the lock nut. 3 -Possible, as new, but unlikely. 2 - good with a little wear. 1 - Bad wear indicated also by about 2 " side movement of the steering wheel each side of centre. Less than 1 means the box is close to end of life but there are lots out there like that. You just get used to it! Bush kits can be found and they may improve the feel a bit. Rebushing can't cure wear in the gear and worm.

[fishyboy]

Hi all,
I have been thinking about trying to adjust the steering box on my '66 131 but I can't seem to find the video on the Amazon Cars site. does anyone have a link?
Thanks
Phil

[Derek UK]

There is no video just a method in the tech tips. I think it paraphrases my posts but in fewer words. It's not high tech! Tech notes/Suspension/Download pdf
extension://bfdogplmndidlpjfhoijckpakkdjkkil/pdf/viewer.html?file=https%3A%2F%2Fwww.amazoncars.co.u k%2Fimages%2Ful%2FSuspension.pdf