“Same” is always open to interpretation :-). Fundamentally the same, or
same down to the very last detail?
Ages ago I had (but then lost) a master listing of all the 400 transmission
identification codes, including Jag, RR, etc. It was from “TurboHydramatic
Division of GM”.
Jag, RR, etc ID codes were all different. Of course the differences were not
actually explained in the listing as it was merely an ID guide. In some
cases the differences might have been very minor…or not.
Even when GM was using the 400 in its own cars and trucks there were quite a
few sub-variations. Different bolt patterns, TCs, valve bodies, modulators,
governors, etc. I remember that some of the late 60s Pontiac governors were
desirable because Pontiac generally specified higher shift points for their
performance cars than Chev, Olds, and Buick.
Most of the internal parts were the same----clutches, drums, etc. except for
a select few HP and truck applications, it seems. There were some HD
versions, I think, used in bigger trucks and motor homes, etc. I dunno.
This is from decades ago. Memories fade.
I believe that Jag 400s were tweaked a bit in '89 or so. I’m sure it’s been
discussed on these pages.
When I was having mine rebuilt I spoke to a couple [what appeared to be]
very experienced torque convertor guys. They agreed that Jaguar specified a
higher grade (and higher stall speed) convertor similar to what GM used in
some of it’s hotter hot rods, as I believe someone here already mentioned,
and that a garden variety replacement would not hold up to 6500 rpm use.
Back in the day (I’m talkin’ late 70s, early 80s here) the old 400s were
often slipping badly and due for o/haul at 70-80k miles. Sure, some lasted
much longer…but many didn’t. I suspect the very soft, long shifts…most
were calibrated that way… contributed to wear, as did lack of care, of
course. But, still, the 400 can take lots of power without flyin’ apart.
Invoices with my XJS showed the trans was overhauled at 70-80k miles or so.
I had to have it re-done right after buying the car (grrrr!) . Turns out a
seal was missing, or installed wrong…something like that.
Sorry for rambling…
Longview Washington USA
It’s my understanding that the GM 400 used in the jag v12’s is the same as
the one used in Land Rover, Ferrari, Rolls-Royce…and yes the TC is furnace
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