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Old 30-12-2011, 09:09 PM   #1
maztech
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Diffs , what's the diff ( rence )

Has anyone ever compared a F and G series diff ,to see what the differences
are ?

Can you fit G series internals into a F series ?
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Old 30-12-2011, 09:47 PM   #2
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you can't
the ring gear in the G trans is much bigger than the F.... so are the pinion gears
axle splines are different too

the other gears and shafts in the G trans are much larger than the F also


what are you trying to do?
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Old 30-12-2011, 10:16 PM   #3
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You can fit F internals into a G...(but why would you).

But as Ed said, no.
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Old 30-12-2011, 10:41 PM   #4
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Just asking the question never had the 2 apart at the same time to compare them and see the differences.
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Old 30-12-2011, 11:46 PM   #5
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The F box is a baby box
The G is it's father.

IMO having thrown around a few. If your not blowing a F box standard on standard 1.8l FP THEN don't worry too much about it.

If you go up to a 2.0L put G in.

IF you turbo the 1.8L make it a little laggy and allow some slip in the clutch and spung centre.

but I've learnt over time it's also about the actual tyre grip and suspension setup. Along with driver and clutch usage on how long the gearbox will last and or if you will break it.

The reason some of us break LSD input shafts etc is because we either have it setup really well or we abuse the living crap out of it or Both.
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Old 31-12-2011, 12:01 AM   #6
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Ta, any worthy mods to a G series while one is stripped down other than a LSD ?
What LSD is best for your $ ?
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Old 31-12-2011, 08:31 AM   #7
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the M-Factory LSD or the stock MSP LSD welded are the cheapest options

early G boxes have thinner cases and are prone to flexing... the flexing will cause the gears to go out of alignment under high loads and that is when it will get stuffed

the later boxes have thicker cases to make this much better, but if you plan on over 300hp, then you may want to machine the case and bolt in steel plates to reinforce the bearing areas



you can swap gears from various other G series boxes to change your gear ratio or questionably make it stronger... I'm sure you know already swapping the 5th gear is easiest

the mazdaspeed b-spec throwout bearing for the RX-7 also fits into the BA's G series box... it won't directly fit into the BJ's G series box without grinding out a little bit of the case... this throwout bearing is much larger and can handle higher loads and higher RPMs better.... my original one nearly blew up after 70000 miles!

you don't necessarily have to put in a laggier turbo... I have a GT25R myself and it is a very quick spooling turbo.... but I eliminated the low end surge of power by shifting the powerband upwards using cams and a better intake manifold... the linear powerband resulted in a much smoother driving car and less shock to the drivetrain, and more fun to drive as the engine doesn't run out of steam at high rpm unlike a stock mazdaspeed
a stock mazdaspeed has lots of low end torque, and has a lot of "kick" at 2000-3000rpm... many modified ones I've seen here make more torque than power! Mine isn't that way at all
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Old 31-12-2011, 09:14 AM   #8
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If you are thinking of puting a LSD into a F series box, I'd still investigate the NA6/BG8 rear diff options. By eye they look similar, but I have never had one next to a F series diff to comfirm it. Must be heaps of NA6 open diffs floating around you can get for free, as no one wants them.
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Old 31-12-2011, 09:29 AM   #9
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Thats what I was thinking to, have to get alot of bits to compare.
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Old 31-12-2011, 09:35 AM   #10
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Quote:
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If you are thinking of puting a LSD into a F series box, I'd still investigate the NA6/BG8 rear diff options. By eye they look similar, but I have never had one next to a F series diff to comfirm it. Must be heaps of NA6 open diffs floating around you can get for free, as no one wants them.
there were OEM options available in japan for the F gearbox
but I'm pretty sure the rear diffs won't work... the axle splines will probably be different, and more than likely the ring gear sizes are different too

it's really not worth trying to do anything to the F series gearbox... they're just rubbish

swapping a mildly built up G series in is worth your while... otherwise, look into a toyota gearbox swap with adapter plate
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Old 31-12-2011, 09:52 AM   #11
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gee really oem options out there for f series boxes? i'll have to investigate those. lol

and as for f series being rubbish, turbo applications yes, non turbo no.
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Old 31-12-2011, 11:10 AM   #12
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Ta, any worthy mods to a G series while one is stripped down other than a LSD ?
What LSD is best for your $ ?
M-factory one or the quife/expensive one. the Ms one ain't rebuildable and you can smash it';s clutchs and still can spin up one leg on the move. the gear torsen can as well but has a much more controllable transfer MS type which is pretty cheap type of diff. IMO A viscous would of been better option considering the Ms don't provide much of a rebuild option. if you could get new shims and clutch peices. I would of put a newring gear on mine and made it tight like my old R31 rear diff. Perfect for drag use
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Old 31-12-2011, 12:41 PM   #13
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the m-factory and quaife has the same problem as the stock MazdaSpeed Protege LSD... they all are "torque sensing" and will free wheel when one wheel is off the ground

the stock MSP "Super LSD" is a conical clutch type, and only are on the spider gears themselves, which provides very long life, low bias ratio, and smooth engagement.... it is NOT the same as the conventional plate clutch type that you find in a kaaz or the discontinued aftermarket mazdaspeed LSDs which have harsh engagement

viscous LSDs don't have a long lifespan when heavily used, nor are they rebuildable... the OEM F series LSDs are viscous ones, FYI

you won't really have to care about rebuildability with the stock MSP LSD nor the M-Factory nor the Quaife anyway because they have much longer service life than any viscous LSD and can sustain higher levels of torque... the helical gear type LSDs (M-Factory/Quaife) lasts practically a lifetime anyway... the rest of your car falls apart before it does!
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Old 31-12-2011, 12:48 PM   #14
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gee really oem options out there for f series boxes? i'll have to investigate those. lol

and as for f series being rubbish, turbo applications yes, non turbo no.
if you take a look on my website, you'll see the OEM options listed

the F series has a weak differential... if you put sticky tyres on and go racing, it wouldn't take long for it to blow up! the early G series also had a weak diff too... the later ones that was used in the BA/BJ, and Kias are much stronger

what I've been trying to say the whole time is, if you're going to spend any money on drivetrain upgrades, put it towards getting a better gearbox... why spend money on crap? of course, I'm not telling anyone to spend lots of money on a toyota gearbox swap... that's just when you plan on making LOTS of power
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Old 31-12-2011, 02:42 PM   #15
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sorry you missed my lol.
i do have a f series, i do have a ba, i do have a clutch plate lsd, i do put on sticky tyres, i do go racing. no blow up yet. have killed rhs drive shaft twice.
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Old 31-12-2011, 03:38 PM   #16
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sorry you missed my lol.
i do have a f series, i do have a ba, i do have a clutch plate lsd, i do put on sticky tyres, i do go racing. no blow up yet. have killed rhs drive shaft twice.
and lower weight bigger advantage again.

The Man I think you have to realise most people need a compromised LSD.
cars can't just be race cars on the street nor do they really want to spend X$$$ amount on car they will get rid of after another 5 years.

I know of several people who have toyota boxed a mazda and know of if not all most car now on new cars. Yet I've owned my Mx6 through out there ownership and still don't mind blowing up the odd box here and there. It's a h box and well reason I have 3 and blown one Torsne LSD up. I don't care.

My point on the MS diff or MSP or what ever is it single wheels in areas the Quaife won't. I know because I swapped between them and changed nothing else. Was a massive difference in performance.

Oh and some of your information on the G box which may becaue you are in the US. They are all similar an do have mixed number of improvments, to make them stronger. through out the years Some may work others do not. but I still think abuse it - it will blow regardless. The early ones don't seem any weaker. To the level that if you mildy turbo a FS - FE or BP you don't really have to go all out.
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Old 01-01-2012, 08:00 PM   #17
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Daniboy have you got any to add, need to build up a stronger box for a particular car.
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