chrisyork said:
Not to my knowledge.
It would have to be a very seriously tuned - and therefore cammy - V8 to justify a six speed. When we had a 10.5 : 1 3500S from new, my father and I were in the habit of pulling away from rest in 2nd and then changing straight into top. Unless we were out for a blast and needing to overtake something in a hurry, in which case third occasionally got used, that was all that was needed for even the fastest progress. The problem with multi speed gearboxes is that it takes time to dip the clutch and swap the cogs. If you have a motor with a good wide power band then you can get on at least as quick by powering across and through other peoples gear change dips. I'm afraid I take the view that a six speed box is prima facie evidence of an overtuned quad valve that comes on cam at 6,000 and runs out of puff at 8! As for BMW needing 7 speeds in their latest offerings.... Mind you it makes more sense when delivered as a flappy paddle automatic.
But to return to the question. The big problem is sorting out the bellhousing and clutch parts for the job. That's why so many people have gone the LT77/R380 or Toyota Supra route. If there's anyone who can sort this out for your suggested boxes its Dellow in New South Wales
http://www.dellowconversions.com.au/index.html. Conversion Components in NZ also do some ready to go kits
http://www.conversioncomp.co.nz/results.php. RPi are also getting in on the act with the T5
http://www.v8wizard.com/TRANSMISSION.php. A number of the specialist V8 tuners in the UK such as Real Steel also do bits and pieces.
You're right - the autos, both V8 and 4 cyl, have a bigger transmission tunnel.
Actually, my recipe for the ideal P6 transmission would be a five or 6 speed ZF auto! And there aren't any bell housings etc around for them either!
Chris
Well, the familial BMW 520i - which is a lovely, cammy straight six, enough torque to do (same 210ft lbs as Dad's old 3500S, and at similar revs IIRC) but loves to rev, has a five-speed, and there's no doubting that it would benefit from a six-speeder. Frankly, the more gears you have, the better your fuel economy is going to be. BMW have ditched their old ZF six-speed autos and gone for the new eight-speeder. Jaguar are likely to do the same soon. Merc are phasing out their dreadful old 5-speed slusher in favour of a 7-speed. VAG use a 7-speed twin-clutch (as opposed to torque converter) unit. Jag are even talking in the long term of 9 or 10 speed autos. Four speeds on a P6 definitely isn't enough, and five is only adequate, not ideal. It's not all about sprinting up to a certain speed, it's having an additional overdriven top gear for economy - which is why, in the new BMW 320d "EfficientDynamics", they've effectively chucked out first gear from the six-speed box and shifted each cog down a row, then put in a "seventh". The consequence is that, even with 163bhp, and about 240 ft lbs IIRC, it'll do 70MPG. The first gear is still low enough to give it quite a decent turn of speed - 0-60 in something like 8 seconds. Those figures, in a 1.5 tonne, 4-door, RWD saloon. Not bad!
Also, having passengered in various six-speed manual-equipped V8s (Holden/Vauxhall Monaro - pushrod LS engine - and a Merc E500, Jaaaag XK8 converted to manual, BMW 540i), I can tell you none of them is excessively cammy, they've all got loads of low-end grunt, but are happy to rev up to 6,500rpm, and further if rev limiters allow. Now, if you want a really cammy V8, try a Ferrari or the current BMW M3 - those flat-plane crank things rev like crazy (peak power usually about 7500-8000RPM, redline about 9000RPM), there's not a lot of torque but there's masses of high end power. The Ferraris, and some Audis, have five valves per cylinder. How that works, I'm not sure. Now, I'd say, if you want that sort of character, don't have a V8, have a smoother flat-six or straight-six, which also would sound nicer, but hey... oh, and not forgetting Formula One! 2.4 litre, quad cam, 4-valve V8s, redline at 18000rpm...
As for the ZF autos - surely the five-speed, if not the six-speed, will just bolt right up to where you've taken off the 4-speed?
Mind you, I still say that the gearbox that shifts gears itself is tantamount to witchcraft and heresy, and that its creators ought to be burned at the stake... =P
