Sounds familiar to me, too. Uneven or sloping road surface. Steering at lock. Backing up especially.

I figure the 240's steering geometry isn't 100% ideal at full lock, so two items are flexing - the tire in contact with the road surface, and the large rear bushing in the front control arm.

When it happens to me, I feel the pop in the steering wheel, and the tire is what springs to a new location reminding me of the stored energy friction cycle that happens in an earthquake.

Gravel surface makes it obvious. Wet surface mitigates the pop. Tire pressure is a factor. Happens with new bushings or worn bushings. Happens on all our 240s.

I've never used poly bushings. And the only way I've been able to confirm a rear control arm bushing has torn away from its inner sleeve is to remove all three bolts in the cup and test it by twisting it.

--
Art Benstein near Baltimore

The older I get the faster I was.