400/412 Automatic Questions

They both used the TH400. The 400's were a little sluggish around town and at low speeds but were OK on the highway. 412's were quite a bit better with their extra torque at very low RPM. Both cars would have benefitted from a higher stall speed torque converter and a shift kit which should be rather easy to source. On both cars the trans feels as though it was set up for a Cadillac.

 

I owned an 85 Jag XJS V12 which uses a gm400 transmission so I may be able to give some help and perspective. The transmission for the jag was set up to shift SMOOTHLEY. It was so smoothe it would burn the clutches up in the transmission, but not for 100k miles. The only difference between the gm400 used in the Jag, and the gm400 used in domestic vehicles was how it was mounted to the engine. It used something like 8-12 mount bolts, instead of the four GM normally uses (or something like that). The GM400 transmission is used because it's highly reliable, and can handle the power of the V12 for everyday stop and go driving. I had the transmission rebuilt by a local transmission place for 1200$, so it's not a big deal. My jag was slow off the line, but that's because first gear was rediculously high. I could get 64mph in first gear taken up to its 6500rpm redline.
The only down side to the automatic is that it's a three speed. That's all. You could probably cruise all day at 130 or higher, but you wouldn't have the get up and go like you would get from the 5. One company sells a 6 speed manual transmission upgrade for all the 3 speed or 4 speed automatic XJS's out there. It improves take off by a second or so, and improves fuel economy drastically. It gives it the feel of a totally different car but it's really expensive. I wouldn't shy away from the auto. But, later on you may have wished you bought a manual. Plus you'll hear the roar of the engine more with the manual.
I hope it helps.

 

Hi,

The 400I and 412 are no race cars but nice to drive. IMO the 400 trans ruins the car. The whole character is changed by the 3 speed slush box. These are also expensive cars to fix. Wait untill it needs a water pump - the whole engine needs to come out for partial disassembly.

Wil de Groot

 

I'm having this battle myself while looking for a good 412 and I posted this quote from a highly respected journalist Peter Dron in a 1988 review of the 412. That seems to sum up the manual question;

'I cannot understand why anyone, other than a partially disabled driver, should wish to by a Ferrari with an automatic gearbox. It seems to me to take a lot of the joy out of the operation and in any case, although once among the world's best, the GM400 used in the 412 seems like a very dated piece of equipment. Ferrari's own five-speed manual may not be the fastest changing gearbox in the world, with a rather long movement, but it is certainly positive, and well sprung towards the third/fourth plane. the clutch, though heavier than that of the average saloon car, is fairly light by the standards of high performance cars. Shifting ratios smoothly is as easy in the 412 as in any of the ZF or Getrag-boxed opposition'.

I've had various opinions of the auto box but the general consensus is that its a ghastly bit of kit to harness to a Ferrari V12. Trouble is you're very limited for choice on the manual as they made very few so if you can live with the auto you'll have no problem finding a load of cars to choose from.

On the 456, it's worth bearing in mind that the early autos were poor boxes for such a modern car.

 

Have never driven a 400i, but I have owned and driven several cars with TH400's... including an XJS.

The 400TH is a wonderful transmission and is awesome for towing, etc... but it soaks up a lot of low end torque and really needs big cubic inches to perform. Having torque high in the rpm band is NOT a good match... which is why the trans works well with say a hot Chevy small block but is horrible with a Jag V12. I would assume, given the cubic inches and torque figures, the Ferrari would be even worse.

One of the Jag aftermarket suppliers developed a cam which would cut something like 2 seconds from the zero-60 times of an XKS...but they couldn't sell it because it was basically an RV-like cam that also dropped about 30-40hp off the top end. That alone should tell you it's a mismatch to the trans.

The Jag was horrible around town but a joy to drive on the interstate. But then a Cadillac is even better on the interstate! ;-)

For my next "big" purchase, I'm torn between an Aston Martin V8 or a 400....but either will have to be a manual trans. I'll buy a Bentley Turbo R if I'm going to be stuck with a slushbox...

Bill

 

Years ago I drove a 400A, but it still stands out in my mind as unresponsive and sluggish. Maybe the 412A is better. What I realized was that with the Auto, you never get to rev the engine, so you will never enjoy the Ferrari sound. I went on and bought a 400i 5 speed instead.