Excuse my stupidity, but what is the difference between:
T4 and a Toploader gearbox?
C4 and an FMX gearbox?
And an LSD and a 9inch diff?

And lastly which one of each best suits a 302 or 351 V8

T4? WTF? or do you mean T5?

a T5 is a different type of gearbox, has 5 speeds, etc, there isnt just one manaul and one automatic geatbox that has been used in every falcon since the XK's

C4 and FMX are different types of automatic gearbox

LSD refers to the internals of any differential that limit slip in situations where traction at one drive wheel is less than at the other

a 9 inch diff is a specific type of rear axle/differential assembly, so called because the crownwheel is 9" in diameter

Yeah, its a T4, its the 4 speed version of the T5, came out in 6 cyl falcons and cortina's.
What i want to know is the actual difference in apllication between the gearboxes and diffs. ie "the FMX can only be used with the 351" or "LSD's are not as strong as a 9inch"
I want to know what i should use, what is best for a 351 or what cant be used with a 351 (as im attempting a 6 to 8 conversion, and am not sure which combo to get)
I do realise that there is more than one gearbox for each ford, which is why im asking the difference, so i know what to get for mine...

the fmx is a big auto and parts are harder to find for them so stay away from them , if you go an auto ( and want to stay old school with a 3 speed which id suggest ) id get a c10 , some call this the c4 , it came out in about 1970 and you tell the difference is that the dipstick goes into the transmission pan ( sump)

depends on the power and hoiw much you flog it depends upon diff and manual gearbox selection

with under about 350hp engine and a auto id stick with std single rail four speed box and borg warner diff , this comes in open center and lsd( so you can lay twins)
if you want a manual and want to do burnouts you need a bigger diff , a 9 inch diff comes out in some 351 falcons up until about 1979 i think and are interchangable easily enough , there are thousands of different mods and parts to get for these so you can change to what ever ratio you want
they come in different lengths ( f100 , xc , xy)i think so check that
the 9 inch sucks more power than a std diff , but will last a fair bit more , they arent unbreakable though

i put a xc disk brake 9inch in my xd which was easy enough
for a very good manual box you cant go past the toploader , this comes in a few versions also
the only problem with a lsd is that you can wear the clutches out in them
to get around this you can put in a spool to lock the axles together but its illegal on the street and rather scary for a newcomer in the wet

hope this helps

never heard of a T4, the 4 speed gearboc used in 6 cyl falcons and cortinas is commonly known as a 'single rail", and IIRC is the borg-warner 807-xxx 4 speed

So, the 4 speed manual i have (out of an XF) is a "single rail" and not a T4 at all?
I would probably prefer a 302, as i just like the idea of having a V8 (plus the sound).
If i stick with a 302 Cleveland, am i correct in assuming i can use the single rail (with a different bell housing) and the disc LSD i've already got?
How easy would it be to kill the gearbox and LSD with a 302 as i dont want to put it all togetherto do one burnout and find out i broke it...

if u break it - you know to make it stronger next time around

if your going to use the 4-speed manuel, then watch the 3rd gear they can go within month(s) of putting it in (experience), the C4/10 auto will take a fair bit of abuse and they have alot of spares out their, use that with a borg-warner LSD and that will be a fun combo.

The borgwarner single rail 4 speed? What happens to them, and what can i do so it wont die? Do i need a toploader instead, as i wanted a manual?

351 + toploader + 9inch is the go

single rail 4 speeds are a bit of a hit and miss affair, i've seen them die with normal use behind a 6, and i've seen them live through 2-3 years of "unofficial" racing/hooning behind a 351 in an XD

thier biggest weakness IMO is the shifter (the nylon nut that holds the shifter in strips out way too easily) otherwise i've never seen any particular component fail repeatedly

not a lot can be done to beef them up, but if you've got one now, run it till it dies, then get a toploader, and the same goes for your existing diff