I am hoping they combined a few processes and are using the front megacast attached to the current floorpan and 2170 battery assembly just like they swapped out the multitude of rear pieces for the rear megacast. That would eliminate all your extra parts and robots and save re-engineering the 2170 battery pack.
Front megacasts were produced long before any of the floorless bodies in white were made and transported to Austin. Without those floorless bodies, they’d have nothing to match up the front megacasts to (or rear for that matter) so they designed them based on what they were currently producing, Fremont MY with standard 2170 pack. There may have been so,Ed early prototypes of 4680 packs at Kato but logic follows that if they designed the rear megacast to work with 2170, why wouldn’t they do the same with the front? They had to know they weren’t going to switch all production to 4680 in the near future so shipping all those front casts to Fremont was just a waste of money if they aren’t compatible with 2170. Anyone who suggests the front megacasts will only work with 4680 are ignoring the timeline and facts. The structural 4680 pack likely came after the megacasts so it was made to match them. Likely they were easier to integrate in the 4680 assembly process since it was brand new from scratch so they started using the there.
For those of you who need this disclaimer, the above is my belief based on the facts as we know them and what logically follows. If you don’t believe in facts and logic, enjoy the 500 mile MY LR+ you are currently driving…
You are correct that new BiW (body in white) chassis examples were shipped to Austin (and Berlin btw) from Fremont last summer.
As for whether the chicken or egg came first, it's doubtful it matters. The new chassis bits were all designed together.
Only the chassis shipments to Austin were shown to be 'floorless'. Not the ones to Berlin, but the video documentation of that factory building wasn't as comprehensive.
Elon said long ago that a 2170 version of the structural pack was designed, and intended as a backup plan in case 4680 was delayed (hello! it ain't soup yet)
Further, the Giga Berlin and Austin open house events showed both packs - the 4680 and 2170.
The difference in implementation was the 2170 pack requires a chassis floorpan, while the 4680 pack IS the floorpan.
Consequently, the fabrication process for the two chassis is different, and sufficiently so that two lines (or a carve-out line) would be necessary in the factory.
If you really sit down and look at the process, the addition of the floorpan changes how all the follow-on bits (like dashboard, seats, the whole interior) come together.
Without a floorpan, it's clearly simpler and faster, requiring fewer steps and robots. It's easy to see why Tesla would be reluctant.
However, you are also correct in assessing that front megacasts can be used with either pack.
It's conjecture, but it seems that the added steps for the 2170 pack negate the time/process/cost savings of the newer chassis design, so Tesla has been reluctant to implement it.
Which brings us to: we would like to see an MiT (made in TX) MYLR to confirm or deny whether they're using front megacasts, or not.
Personally, I'd like to see a 2170-based structural pack chassis, as it's a step forward with several benefits.
But I don't think they're doing it.....logistics, order backlog risks.....there are many issues.