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My question: Is there any technical/engineering reason to NOT heat the brackets that attach the rear springs of an F3 to the frame?
I am doing a disassembly of my son’s 1950 F68 (F3) to see what parts I need to scrounge up. There is a ton of play in the spring eyes which can be the result of wear to the spring eye pin (also called shackle bolts), the bushing, or the spring itself (or all 3).
My attempts to drive the spring eye pins out have so far been unsuccessful, and yes, I did remove the little bolts that anchor the pins! The parts were repeatedly soaked in penetrant over a period of days, and then I attempted to drive the pins out as described by the factory manual. I used a combination of both BFH’s and a rather powerful air hammer that I borrowed from my mechanic buddy. These things are showing absolutely no sign of any movement at all.
It would appear to me that I have 2 options. The easier option is to heat the brackets up with my oxy/acetylene torch and then try the air hammer and BFH again. I just want to ensure that there are no valid reasons not to heat those brackets as the last thing I need is to wreck them, thus adding more hard to find stuff to my list!
My 2nd option is to knock out all the rivetts, unhook the axle u-bolts and then bring the spring assemblies over to my shop press. This is a lot more work, so I’m kinda hoping option number 1 is OK.
I could be wrong but I don't believe it to be a frozen pin issue where heat would help to fix. It appears to be more of an alignment issue where a combination of the lips on the worn pins and springs and hangers are conspiring against you, hanging up inside together. You can see the misalignment in the pic you posted here. I don't have any better answer than to try to take the load off and wiggle it around and pray it comes apart. I had a similar issue trying to disassemble the king pins on a F6 front axle I was parting out. I never did get to come apart and ended up scrapping the whole assembly.
Actually my first thought was a lip that was hanging up, so I decided to test for that. The truck is on axle stands, so with a long prybar its super easy to wiggle that spring eye up/down/left/right etc. I enlisted a helper who wiggled it everywhere, and at the same time I was running the air hammer against the pin. Zero movement. And when I say "zero", I mean absolutely nothing. As a 2nd test, I alternated trying to move the pin & out. Again, absolutely zero movement, so this is why I believe it's firmly rusted in place. This truck clearly received zero maintenance and I suspect these pins have been in place since Harry Truman was your president.
So if it is actually seized, can I heat those brackets safely?
Here is a thread with a lot of great informatiom. On post #4, Ross suggests making a great tool for this job. It will greatly help. But of course you will need to remove/lower the differential from the leaf springs to get the tension off the the spring pings to make it work.
