Good evening to the Classic Oldsmobile forum. Vehicle being worked on is a 1966 Ninety-Eight Luxury Sedan. I need help with what the tread size and pitch - looks like a fine thread - would be on the shaft which acts as the pivot point for the upper control arm bushings. I wish to clean up the threads on both the shaft and large fasteners which hold the bushings in place. Picture included from the service manual. Thanking all in advance, regards, Howie.

 

I think they are 3/8" diameter 24 TPI or as you stated NF/national fine thread. 3/8" NC/national coarse thread would be 16 TPI.

 

Thank you Sugar Bear. Failure is not an option for me, I was able to locate a tap and die set, though no part in the kit would fit the parts in question, the thread pitch turned out to be an 18, and with my, caliper, the width in total was 5/8. 5/8 X 18 is the size. Again I appreciate you reaching out. Best regards, Howie.

 

Sorry for the wrong information, I should have looked at the picture more closely. I had a different style in mind. Glad you figured it out.

 

Just to clarify, the control arm bushings do not "pivot" on the shaft. Once you torque the shaft nuts (with the suspension at ride height), the center sleeve of the bushing is locked to the shaft. Correct replacement bushings even have teeth on the ends of that sleeve to ensure this happens. All "pivoting" is actually torsional stretching of the rubber in the bushing. This is why you need to lock them in place with the weight of the car on the suspension.

 

Do not worry, I am grateful you reached out regardless. Often we only hear crickets when it comes to the large Oldsmobile cars, any help is always appreciated. Main thing is, this appears to be resolved! Best regards, Howie.

 

Thanks for reaching out Joe, I stand corrected. Best regards, Howie.