bad steering box?

[GTV67]

On my 67 Super with a ZF steering box, the steering feels just fine every morning. Sharp turn-in, no play etc.

Then, in the evening, when it's warmer and I have to drive uphill for 10 miles and so everything gets hot, the steering just goes away...basically there seems to be a lot more play right at the center of the steering, which makes the car quite hard to drive up a twisty hill (17 for the Bay Area residents). It's pretty disconcerting, and when I get home I can move the steering wheel and look at the front wheel and there does seem to be a lot of extra play - this has vanished by the time of the next drive.

I got some advice on steering box play adjustment - tighten screw until very slight resistance is felt at the center of the steering. I did this, noticeably stiffer steering at parking speeds, but no problem above 10mph...but that evening the play returned. I wasn't sure what oild to use in the box so I used the ame Spirax I use in the transmission.

All steering ball-joints and linkages and all other suspension bushings are brand new. When it's cold, the car handles like a dream

any ideas?

Thanks,
-Richard
Scotts Valley, CA.

[Andrew]

That's odd.

In my opinion, ZF boxes suck compared to Burman. I had Norman Racing go through the ZF in my Super, making a good one out of two I had, and it's still sloppy on center, because they can't realistically machine the pieces without special tools they don't have. So they used the best races, balls, etc.

I don't have a good answer for the heat issue, unless something is greatly expanding due to the exhaust heat nearby. Do you have tube headers? Maybe craft a heat shield between the headers and the steering and see if that helps?

Any decent 90W oil ought to be OK in the box.

Andrew