AF Nikkor 35-70 f2.8

[Dez]

I have one of these very handy lenses, but it has an annoying problem. When I operate the push-pull zoom control, the whole front group moves about a millimetre before the zoom action starts. The actual focus ring is smooth and without excessive play. The movement appears to be forward of the aperture bladesThere is obviously something loose in there which might be easy to fix, but this is a complex lens and I am gunshy about digging into it with no prior clues.
Has anyone out there done this repair, and who could give me some guidance? Or failing that, a link to a repair manual for this lens?

Thanks,
Dez