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Popping noise from front suspension

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1973 pinto wagon... 205 70 14 tires 82000 miles on factory suspension, new tie rod ends 7000 miles ago

I hear a popping noise and a small jolt when backing up with the wheels turned fully to the lock.

No  steering problems otherwise, no while shimmy at speed

Alignment good tracks straight on the road, I can take hands off steering wheel at 70 mph qnd car tracks straight

I have inspected the front suspension and have had it inspected by an alignment and suspension shop and nothing seems loose, bent or broken.. some play in the lower ball joints..wheel bearings tight, new sway bar bushings, no play in steering rack.

Only happens when reversing  with wheels turned to the lock.

Could problem be that the steering geometry causes the wheels to set to a non parallel track and the oversize tires then deform rather than slide and then "pop" back into place.

This has occurred since i bought the car in 2016 7 years with 62k miles and hasnt gotten and nothing has broken

Any ideas?

I don't have an answer but want to say that the design of steering geometry is all about going forward, not backwards. So, that might be the problem right there. If the lower ball joints are somewhat loose perhaps they stay in their socket under normal forward driving but the forces generated by backing up cause them to move.

As most people know when a car turns the outside wheel follows a wider arc than the inside. This is the Akerman effect and the compensation is designed into the steering geometry. Because the Sunbeam Tiger went from the Alpine steering box to a rack & pinion the position of the rack was far from optimal. The Akerman is so bad the outside tire turns in more than the inside.  As if that wasn't bad enough when backing up at full lock one tire is almost dragged sideways. The forces are so great that the lower A-Arm fulcrum pins have been known to break! I'm sure the forces in the Pinto aren't that bad but I said that to illustrate what can happen in the extreme. The wider than stock tires may not help your situation. Hopefully others can give you more insight.

If you have someone with a gopro could put it in the wheel well area safely so you can see what is happening

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I found the source of the pop/clunk..

Jacked up the passenger side wheel, removed the wheel and discovered that the 50 year old upper control arm bushings are deterriorated and need replaced..

So im adding that to the maintenance list.

Awesome glad you found your problem

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