V12 Engine Thought Experiment - the reverse lump

I recall from Kirby’s book that the V12 engines in the XJ-S and XJ-12 were GM TH400s with a different case to match the Jag bolt pattern. Even the dowel pins are in the same locations.


Does the rear end of the Jag-version TH400s have the same tailhousing and tailshaft? Because if they do, that opens the possibility of a reverse lump.

For example, I have a Chevy 4x4 pickup with a 350 and 4L60 tranny. If the aft end of the Jag-version of the TH400 can marry to ‘regular’ TH400 components, then I could theoretically swap my Chevy 350 and 4L60 for a V12 and a TH400 (a much stouter transmission for which many aftermarket performance parts are available) married right up to my transfer case so I would maintain 4WD and the rest of my driveline. (It is no problem to marry a TH400 to a transfer case.)

Is this feasible?

Probably feasible. You’d certainly end up with an interesting vehicle. You’ll probably get a lot of puzzled looks from your redneck friends.

John N - don’t know if these pics will help - here are three pics of the tail end of the transmission used in the XJS with the V12

- sent 3/3/2021 0852hrs. EST USA.

Golly, that sure seems the same.download (1)

That would be the best part of it.

I guess now I gotta keep an eye out for a good V12 and TH400. Sad to think of how many have passed through my hands and are now gone.

When the LT1 in my 96 Roadmaster Wagon croaked, I was minutes away from deciding to fit a carburetted V12 manual,.

I decided the electrical and pipework systems of the car would probably give me more grief than I wanted but the prop-shaft connection didn’t cause me any angst as the shaft end can always be changed to suit the trans.

Mostly though it was two other pre-existing projects that decided me against spending time doing bespoke work and trouble-shooting on a workhorse load-lugger vehicle. If I’d had nothing else on my plate I’d have enjoyed busting the conventional swap route. Instead I just replaced the LT.