1)I am told there are long and short, but the chassis accomodates both. What are the differences, is the long box better for cooling the oil, as bigger, or does the long box take the 6 gears and the short the 5 gears?
There are long and short boxes - both G50s, the . A short box looks like this
There are 4 speed boxes (they're the long ones and have a cable operated clutch so require you to fabricate your own operation mechanism - avoid these) and 5 speeds (the most popular). The G50 gearchange mechanism can be centre or driver side mounted although, the central rod linkage takes a more protracted route to the gearbox which personally put me off a bit.
The 6 speed is the Getrag 'box which is more expensive, but is short (quite a bit shorter than a short G50 in fact) and uses a neat cable shifter (centrally mounted in the cockpit). I believe that the factory make a neat cowel for the gearchange too which looks the business. The 6 speed obviously uses shorter ratios as there are more gears to play with. General feeling seems to be that the G50 ratios are better suited to the Ultima, but that's down to your personal preference.
2)What I am looking for is a box that gives good acceleration in all gears. I am not interested in 200mph, but really topping out around 150-160mph, as this is mainly useful for uk roads and short blasts. I prefer low down speed, low down generally to 120mph, so is a 6 speeder better for and not use the other top two gears or a 5 speeder with low gearing. My friend has a Diablo, so roughly the same power output, around the 600bhp figure, but obviously heavier, he rarely uses first and generally won`t drop below 3rd unless in slow moving traffic.
Right, there are a couple of variants of the G50 in terms of ratio and LSD. Here's the info to tell what's what:
1987 911 G50s have an 8 digit code stamped in the bottom, for example 'G50/0073H'_'12/00050'
G50/00 = G50 trans
7 = trans for 6 cylinder
3 = 5-speed Rest of World; 4= 5-speed USA/Japan/M298)
H = 1987 model
00050 = serial number
A 1988-89 trans has a 12 digit code, such as 'G5000 1 J 00903'
G5000 = trans type (see below)
1 = normal differential (0= no diff, 2= ZF ltd. slip diff)
J = 1988 model (K= 1989)
00903 = serial number
G50/00 = 911 Carrera, R.o.W.
G50/01 = 911 Carrera, USA/CND/J/AUS
G50/02 = 911 Switzerland (very short gear ratios)
G50/50 = 911 Turbo world wide, 1989 only
G50/52 = later Porsche turbo boxes ZF ltd. slip
I've got a G50/02 which is a short ratio box with LSD. This means that whilst I can't do 200mph (or I don't think I can
to my mind it's more usable day to day and has the benefit of having LSD fitted as standard. To retrofit something like the quiaffe ATB is more than 800 quid for the diff alone!. The G50/52 from the Turbo has LSD, but is the other end of the ratio spectrum using very long ratio's which will give you less 'urge' on acceleration (if that's possible with 614 ft/lbs of torque!).
3)There has been a lot of talk about changing the gear ratios, but is this needed for road use, I understand for track use, you want it suited to the track.
The G50/00 ratio's are fine. In fact, you could live with any of them but see comments above.
4)Which box keeps the driveshafts as straight as possible, so no chance of snapping driveshafts, as they maybe at a different angle?
Good question. But the differences between them are marginal and don't have a significant effect on the driveshafts. The only exception is (wait for it) supercharger installations. The engine has to move back a little to clear the bulkhead (for which the factory supply an adaptor kit) which offsets the drive flanges a little - but again, not enough to be a problem.
5)Are the long boxes used for the higher bhp engines as stronger or what. Sorry to ask so many questions in one hit, but I need to understand, so I don`t opt for the wrong box?
Nope. All G50's are the same strengthwise (Turbo included). The tyres will spin/clutch will slip before gearbox gives in anyway (he says