My approach was to lift the body, leaving the engine, transmission, differential, suspension, and PPF as a unit. The PPF is the Power Plant Frame, a beam that connects the differential and transmission. Lifting the body was largely uneventful, but with one BIG surprise.
There is good help on the internet. Here are some links:
- Start by removing the dash (DashRmv_89_93, by Anthony Meeks).
- I do not know the author, but the nine posts starting at Removing miata donor parts 1 of 9 or where do I start? are the best I found.
- This post by mavidal was also useful Miata – Removing the Uni-body from the PPF.
I started by draining the fuel tank.
Then remove the dash. The link above helped a lot.
Take out the wiring harness. I tried to put labels on all the connectors that I disconnected.
I built a frame to support the body and then lifted with an engine hoist.
And walked the engine, transmission, PPF, differential, and suspension out from under.
But do you see the dangerous flaw in the wooden frame I used to support the body? I claim to be a mechanical engineer and should know better. When I designed the frame, I always imagined the body being supported at the front and back simultaneously. So the wood legs were attached to the cross beams from which body hangs. Here are some sketches showing the problem.
First, here is a schematic of the frame. The straps to the body were attached to cross beams that were directly above the legs. When designing this, I imagined that there would always be a load from the front and rear of the body. Things are fine for this condition.
But when I was lifting or lower the body with the engine hoist, there would be times when the frame carried only the load from the front or the back, not both together. In that situation, the frame can rotate and is unstable. A contributing factor was that the rear of the body was a lot heavier than the front.
One fix would be to extend a support foot to the bottom of the frame.
So, as I was lowering the body, I did push to align it and it went unstable. The car was near the ground and the frame rotated up. No harm done, but a surprise. I do have a rule that I never go under a car without two redundant ways of holding it up, but still I did not like to see that I had missed so basic a failure mode.
