"How I Do It"

Sure Grip Spacer Pin

I have a 1965 300L with a leaking driver's side rear axle seal. In order to replace the seal, the axle has to come out. On cars without Sure Grip (*), it is a straightforward job. On cars with Sure Grip, pulling the axle almost always results in problems from the spacer pin.
"Spacer pin" isn't the right word. The service manual refers to it as the "Axle Shaft Thrust Spacer" and the following pictures show it in detail. I will refer to it as the "spacer pin".

This is the cross section of the differential. The spacer pin is partially visible
between the axle shafts. The next picture shows a better view.

If you were to disassemble the differential, you would get the pictures above and below.
The spacer pin is clearly shown.

The spacer pin pieces are supposed to stay together with the "lock pin", which is really only a roll pin. In real life, the roll pin doesn't last long and when you pull an axle, the spacer pin pieces don't stay on the lock pin. Instead it comes out with the axle. It would be nice if the pin stayed on the end of the axle but either it falls into the differential sump or falls on the differential gears where you may be able to retrieve it.
If the pin falls into the sump, you have no choice but to pull the other axle, pull the differential, fish out the spacer pin pieces, install them in the differential, install the differential, and the axles. Be prepared for a 2-4 hour job with stinky oil and heavy parts.
On this car, I got lucky and could see the spacer pin sitting on the differential gear. If I could retrieve it, somehow stick it back on the axle, I could save myself a lot of work. I found a piece of aluminum wiring conduit about 36" long and perhaps 1" in diameter. This is long enough to fit down the axle housing to the differential, and small enough to fit through the inner axle seal. To this piece I taped a magnet.

The conduit.

The magnet on the conduit.

On the first attempt, the magnet found the pin and came out.

I cleaned the end of the axle and used Super Glue to attach the pin.
The pin and the axle went back in and the job was done.

It is important to check that the pin made it back to its home. With the axle bolted in, check for backlash. If you can chuck the axle in and out just a little, as in .015", the reassembly is right. If you can chuck the axle in and out by a lot, such as .125", it is likely the pin fell out before it made it home and the axle will have to come back out.

(*) Chrysler's version of a limited slip differential is called "Sure Grip". I am familiar with the versions used from 1957 through 1966 but this discussion may apply to other years as well.