I keep seeing FACELIFT? what is that

I know everyone likes to beat up on the TH400 but that thing is a bullet proof torque monster. It went into GM’s best muscle cars of the era…
Chevelle’s, Camaros and Corvettes. Heck it went into Hum Vee’s in Desert Storm.
Jaguar or Even Rolls Royce didn’t know how to build a seem-less automatic transmission if their life depended on it.
If you really want to light up tranny look at your hoses, modulator and install a shift kit. Not too many humans can change gears in a manual gearbox as fast as a good auto box but hey what do I know.
Change out your diff gear ratio and go have some fun.
We are all not getting any younger but if you want to change gears in a 4000lb car go buy a C4 Vette. I thought many times about changing it out but I’m good for now. Just need a cruiser.


I ‘think’ the Corvette, Camaros, etc had the TH350. My 72 Camaro did.

It’s pretty much just a lighter duty TH400. Just as bulletproof. The TH400 was more for trucks and Cadillacs.

And you’re right, a very bulletproof transmission. Popular in dragsters because of the torque it can handle.


Greg you need to up your game, the 402/ 454’s Chevelles got the much coveted 400TH. We like to beat this tranny up but stick with shift kit and gear ratio change. You’re good to go!

The ratios, shift points and power bleed are why it was a very poor decision for the V12, plus you add 2.88 rear gears, and the chevy van it belongs in, will nuke you to 60.

It needed a 3.54 and a T700R4 by 1983, or better yet, a Mercedes trans.

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Simply not true.
Heated seats can be fitted - life isn’t the same without - ABS is useful despite being a government mandate, so are seat belts. Some parts got cheaper, some wher improved in other ways. There’s no single perfect XJS for everyone.

Building a transmission is very complex and expensive. Instead of such a huge undertaking the better choice is to get the best for the job that is available. And stick with it. More speeds would have been much better… but behind a V12 some will have preferred fewer gear changes.

Everything you said is 100% true.

Nothing you said addresses the parasitic drag on torque. Of course it can absorb the torque. It absorbs most of it, and doesn’t leave enough.

And even with the 2.88:1 rear end, 70mph cruise is about 3,000 RPM.

Yes, I can change modulator, and install a shift kit. And that won’t make the shifts any smoother.

I had a C4 Vette. That had a six speed. Put that six speed in the Jag and I’ll be happy. Leave off the forced 1 to 4 shift. I can do that part all on my own, if I want to.

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Seat belts = good. Would use them even if I didn’t have to.

Motorized seat belts that don’t really address the problem when they do work, add weight whether they work or not, are mandated because the average person didn’t have the common sense to actually use seat belts that worked, and are otherwise a kludge to the problem? Not so much.

Airbags are also good. I just wish I could replace my over 30 year old air bags.

I’m also in favor of using ABS. I’m not a luddite. I’m just not sure you can call it DYI friendly. And I think the Teeves III system can be described as “not ready for prime time”.

Total garbage and never even sat in a car so equipped but it’s such a strange concept…

I once had a 91 VW Jetta that didn’t have airbags. It had a much better way i think than the xjs. Shoulder belt simply attached to top of door. So you’d sit down, and simply closing door put that shoulder harness over you.

Of course, not sure how good an anchor point the door would be?

Depends; if there’s a catch in the door and the door can take the ~600 kilos required… can a 91 Jetta even take 600 kilos as a whole?

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Fair number of people were killed, including a friend of mine, when in a relatively otherwise-survivable accident, the door popped open and puked them onto the street.

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If the seat belt is anchored to the top of the door, that top corner of the door needs to securely latch to the door top jamb and to the top of the B pillar to have any chance of staying put in an accident.

Then once in an accident, getting that door open will likely be a serious challenge, and if that door doesn’t open, that belt may very well be keeping that person from getting out of the car.should they be able to and need to get out.

That seat belt may keep them pinned in the seat. Which might be the last seat they’ll even be in. That would not be a good way to go.

There was a buckle release at the center console.

That would address my ‘getting out’ concern, but there is still the ‘how is the top corner of the door’ secured concern.

Correct, domestics were even worse, as the crap build quality on a largely plastic door that housed the entirety of the three-point system, effectively crushed inward.

On the VW, sans lap belt, you could at least dive away from impending doom, but not really.

That reminds of the seatbelt chime in that car - the first bars of La Cucaracha :crazy_face:

It doesn’t: I have a dead friend because someone thought it was a good idea.

Did those door seat belt load points securely latch into the car body, or just rely on the weak window surround up and across the window, and a typical door latch to not only hold the door closed, but to withstand the loads placed on the shoulder belt?

I’m suspecting ‘typical’ door latch and no special latching at the top corner of the door.

Yes: the car had the “special latching,” at the top of the door, as all of them did. None of them relied just on the window frame. It still failed and killed my friend.

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As a novelty item the V12 has huge value :slight_smile:

Personally I’ve loved my two V12 Jags. But it’s mostly a vanity thing. I get enjoyment simply from having something a little different. And I get some satisfaction from taking on the challenge of keeping in good working order.

The beauty of hobby cars is that not everything has to be practical. :slight_smile:

The Delanair systems can be a real PITA no doubt about it.

I’ve never felt that automatic climate control …on any car…was a “plus” but buyers of upper-end cars expected such convenience features. Personally I’ve never felt that having a manual control HVAC was a misery ! It isn’t beneath my station in life, nor a great effort, to adjust a couple of control knobs.

Which cars got which transmission was actually a bit complicated depending on a slew of factors. But, yeah, the TH400 was used even behind some of the smaller engines.

Officially the lighter duty version of the TH400 was the TH375. And the lighter duty version of the TH350 was the TH250.

The TH400 was built in countless sub-variations depending on application. A great transmission in many respects. In the luxury cars, though, they were calibrated for very soft shifts and as a result often didn’t live very long lives. Overhauls at 80k-100k miles were fairly common.

The bugaboo with the 400 has always been that it is very parasitic. Back in the old days some hot rod guys ditched the 400s for 350s to pick up about 10-15 usable horsepower.


With some tweaking the TH400 behind a V12 can be made more responsive and thus a bit less annoying.

I went from 2.88 diff to 3.31 in my Series III V12, still with the 400 trans. Naturally the difference is pronounced; like a different car. And, naturally, the highway speed RPM is a lot higher than we’re accustomed to these days. For me the trade-off was good.

Jaguar’s version was problematic and subject to a recall to fix certain problems. For many years (and maybe still?) the parts needed for the recall repairs were not available. Not a good situation. How Jaguar got away with this for so long is a mystery to me.


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My 88 has factory lattice wheels which I personally think are fine