FC diff ratios

[initial_j]

are auto and manual diffs the same or are autos shorter?

an are fc and fd diffs interchangeable?

basicaly after the shortest ratio possible for my fc which will be a skid car, wondering what the options are?

[turbotoaster]

an auto will be a longer diff than a manual.

the manual diff on an fc is a 4.30, the manual on a fd is 4.10 so its longer, they are interchangable but i wouldnt recommend it as its longer

probably the cheapest solution is to either track down a diff off a rx8  as they have a diff ratio of 4.444 or if you can get a late model diff as they are 4.777 which is super short

[initial_j]

an auto will be a longer diff than a manual.

the manual diff on an fc is a 4.30, the manual on a fd is 4.10 so its longer, they are interchangable but i wouldnt recommend it as its longer

probably the cheapest solution is to either track down a diff off a rx8  as they have a diff ratio of 4.444 or if you can get a late model diff as they are 4.777 which is super short

auto diff longer than manual? that definate?

i dont have much experience in mazdas but from everything else ive worked on auto diffs tend to be a fair bit shorter ratio?

do rx8 diffs fit straight in or do you have to swap the casing?

[turbotoaster]

yes an auto diff is longer than a manual diff.

remember the fd auto had 4 gears and the manual had 5 so it makes sense to make the diff longer to compensate.

I know the fc diff bolts straight up to an fd as a friend did it, so i assume its the same the other way around.

when people have put an rx8 diff into a fd they have just taken the final drive out of the diff and put it in the fd casing, it may bolt straight up complete but thats something i dont know about, maybe ask on rx7club

[SiH]

Err, I\'d double check on that auto thing dude - as said above, auto cars tend to have shorter final drives than the manual equivalents.
The whole 4/5 speed thing is totally irrelevant - my auto 14a has a shorter final drive than it\'s manual counterpart, and that\'s 4 vs 5 speed
In fact, the auto S15 has a shorter final drive than it\'s 6 speed equivalent.

EDIT: Google suggests that the auto diff is circa 3.9...

[turbotoaster]

for example,

fd manual diff, 4.10
fd auto diff, 3.90

it maybe the different for other manufactures but not for mazda rotarys.