I would lift one side under the spring seat. Block it up with 4X4 cribbing, jack up the other side, block it up. Work under the car. That is until I coughed up $1000 and bought myself a used 9000 pound lift.

Given options 1 or 2, I would go with 1 and block it up at the ends of the axles. I hate jack stands. Even on concrete.

The compressive strength of the lowest grade of cast iron is 83,000 psi. Tensile strength is 22,000 psi. You can safely lift 2200 pounds on a surface area of 0.1 sq.in.

Greg

I have a little jack like yours, but while I use it in the front, it's too small (too short a reach) to jack it up from beyond the rear bumper, so I use a 7,000 lb jack that has a long handle (that I can reach from well behind that bumper).

But my concern is, whatever jack saddle you or I have, with any metal saddle (and particularly one with a cup) we're really only applying lifting force at one or two tiny points where the saddle touches the differential.

My key suggestion is that I (and you should) use a block of wood perched on the jack's saddle, and use that between the saddle and the diff. Such blocks tend to spread the points of contact over a larger area, and being softer, doesn't stress the metal diff's housing as much.

Of course, a block makes the lift a little less stable, but after raising the car you're certainly going to finish off by stabilizing the lifted car with good jackstands, right?

I've considered this about as carefully as you have, and try to aim for the flat spot just behind the rib, like your second drawing shows. Difference may be, my jack's cup is aluminum alloy with maybe a quarter inch of cup depth, inset with a rubber disc about that same thickness.

Some of our all-240 fleet are equipped with steel rear covers and drain plugs on the flat, so my objective is to avoid those two features with the jack's force. I don't suppose I could hurt the drain plug but I like to avoid puncturing the jack's rubber cushion, and of course avoid putting force on the cover and its gasket seal.

Interesting post!


--
Art Benstein near Baltimore

Show me a piano falling down a mine shaft, and I'll show you A-flat minor.

version 1. it can take the load. version 2 could crack yer head like a hardboiled egg.