Hello, I happen to have a TH400 from a v12 xjs on hand and a full rebuild kit and very mild shift kit that I was going to use for my v12 project but decided to go manual transmission so it’s just laying around now. I wanted to know if there is anyone here who has done it and how do they like it? my BW66 seems to be unhappy as of late as it makes some “interesting” noises when you shift it manually, and it sometimes slips on the 1-2 shift. I figure rather than trying to rebuild a transmission I dont like very much I may as well try and use the perfectly good th400 I have laying around. I know that the TH400 has a slightly shorter 1st gear the should make acceleration from a stop slightly better plus they are simple as hell to rebuild compared to the BW66.
I’ve never done it so you can take my words with a grain of salt.
Despite the obvious appeal ( you already havethe transmission) it isn’t an ideal choice in my opinion. One drawback is that the 400 is notoriously parasitic…and IMO the 4.2 engine doesn’t have much power to spare to begin with. There are better choices, IMO, but you’d be spending more money.
How were you planning on mating the 400 to the engine? For the limousines Jaguar used an adapter, item #19 in the illustration below.
Cheers
DD
If it’s making noise and is slipping maybe increasing the pressure will help for a while. Maybe the tv cable just lenghtened or ist beginning to die? At the throttle body.
Are your shift points, stall speed in order?
For the hassle of a conversion i would try the 4 speed transmission with direct drive, not that old thing (which you might be able to sell for some money?)
Otoh, if you like it why not.
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Have you checked band adjustment, William…?
Frank
xj6 85 Sov Europe (UK/NZ)
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Thanks for all of the reply’s, I did more research over the last few days and decided If i’m going to go through the trouble of swapping another transmission in some day its going to probably be a ZF from the XJ40 or even an 8speed ZF from a 328i BMW. For now though I am going to go through the BW66 and test the line pressure and check the adjustment of the bands. I also noticed that it isn’t kicking down when it’s supposed to so I would assume the kick down is out of adjustment as this engine and trans combo has been out of the car before.
Again, check the throttle cable. It can be either torn or loosened. Mark position and tighten it from there; as harsh as possible is better. Ideally you would set the pressure with a gauge per the manual, but I eyeballed it and it turned out to be to spec.
The transmission won’t like being out of adjustment for long; the bands wear quickly.
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It is not really a kick-down, William, it’s a ‘downshift’ cable - which is an integral part of the shift behaviour. It tells the box the driver’s intent by the position of the gas pedal…
With light throttle input; the box rapidly upshifts - heavy throttle delays upshift. From high gear at slow speed the box should downshift if the pedal is used even moderately…
Proper adjustment require measuring fluid pressure at the take-of point. However, check at the cable adjuster; when the cable is adjusted, a ferrule is crimped on to the cable.
Check clearance between the ferrule (if present) - it should be 0,4 mm/0,01". Adjust as required…
But slipping is usually related to band adjustment - and require prompt action…
Frank
xj6 85 Sov Europe (UK/NZ)
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Thank you, for the info. I am following the factory service manual procedure. I already have the adaptor/extension tool for the service port and I have a proper gauge for the job. What I noticed with the slipping though is that under moderate to full throttle it does not slip and the shifts are as crisp as can be expected from an old slush box. It only slips a little under very light acceleration and only on the 1-2 upshift. Is that characteristic of out of adjustment band?
Not only that, Frank, but it also influences shift quality: the more torque the engine produces (per throttle position), the harsher the shifts are. A disconnected cable gives almost imperceptibly smooth upshifts and is in 3rd below 30 kph. If it is too long the shifts are too smooth and it might never do any kickdown as it will never measure full throttle.
The tv cable operates a cam in the box with a special profile (the detents you feel in the pedal). This controls a plunger that varies line pressure in conjunction with pressure from the governor (output speed), while overall pressure is determined by pump rpm (input speed). I thought the TH were similar.
What you describe might well be the band and I think it’s reasonably easy to adjust per the manual.
As much as I‘d like to see an 8-speed it would be a lot of work to get the electronics working?
It would be but I know some companies like Megasquirt make some aftermarket DIY controllers. If that doesn’t work I’m sure some company over in Europe has thought of something. The ZF 8-speed is used in a lot of cars so it would surprise me if there isn’t a stand alone solution out there.
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It’s difficult to tell, William - other factors may come into play…
Like; shift quality mentioned by David is a function of application and release of bands and clutches. As bands/clutches are applied by hydraulic pistons, fluid is squeezed out between band and drum - there is an imperceptible slip before the two locks together. If for some reason ram pressure is marginal - lock-up may be delayed…
The valve body is responsible for synchronised application and release to change gear - if release/application is out of sync; there may be a brief period with none is applied - appearing as a slip. Which indeed may be an anomaly between the three pressures involved; engine driven fluid pump, downshift cable adjustment and governor pressures - confusing the valve body…
Band adjustment cannot be excluded. But in any case; as you are prepared to the relevant adjustments by the book - it should be clarified, and come right. There does not seem to be much wrong with the box…
Frank
xj6 85 Sov Europe (UK/NZ)
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I am still going to do the tests but I am sort of embarrassed to admit this but for the kick down issue all it was, was the throttle getting stopped by #2 injector hose that I replaced a while ago, and made too long so it hung down in the way of the throttle. now that I fixed the issue, it kicks down just fine, and the shifts are nice a smooth. I also topped off the fluid and that seems to have stopped (for now) the slipping.
Good work well done, William…
Frank
xj6 85 Sov Europe (UK/NZ)
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