Question about mix/matching GT-FOUR parts

[angryface]

Hey guys, I'm doing a GT4 conversion on my Mazdaspeed Familia GT-R, this has been done before. It's known that the ST205 is the strongest and most refined of the GT4 drivelines, so if I can use those parts I will. It's economical for me to purchase a ST205 rear end from Japland, but shipping costs equal that of the transmission, so I'd prefer to buy one locally. The ST205 Celicas weren't available in Canada, but the ST185s were, and I managed to find a couple of transmission locally.

The question: Can I use a ST185 front-end with a ST205 rear-end, using either a ST185 or ST205 propshaft? If not, what would be the issue preventing that? Gearing, length of propshaft, something else? Thanks

[ee904age]

Im not sure about gearing, but I would guess the the shorter wheelbase of a Familia would require a custom driveshaft anyway. Why not just leave the stock GTR rear end in there??

[strx7]

Im not sure about gearing, but I would guess the the shorter wheelbase of a Familia would require a custom driveshaft anyway. Why not just leave the stock GTR rear end in there??

because the rear diff and the transfer box need to be the same ratio

[angryface]

So I guess that means... no, drats.

Actually, the driveshafts fit perfectly. Well, we use spacers for the rears to push it out about an inch, but they even fit in our hubs perfectly.

[iOnic]

He meant the prop-shaft from the gearbox to the rear diff

[Malcolm]

all GT-Four rear diffs have the same ratio, mixing a matching ST185 and ST205 boxes and diffs will be fine. They might even be the same part anyway

[angryface]

Good info you guys, thanks.

For axles, ST185 and ST205, I heard that they're interchangeable in a ST185 gearbox. I haven't found anything about the hubs, do the hubs from both generations accept the same diameter + spline count axle?

[strx7]

in the front i know they interchange, cant see why the backs wouldn't

i'm 99.9% sure the outers are all interchangeable. 4wd corolla and gt4 all have same splines

[DeeCee]

there are some differences in width and control arm locations between st185 and st205. But that is a moot point since I imagine that you'd be making up new mounting points for the control arms to attach to.

[Scottie]

Good info you guys, thanks.

For axles, ST185 and ST205, I heard that they're interchangeable in a ST185 gearbox. I haven't found anything about the hubs, do the hubs from both generations accept the same diameter + spline count axle?

ST205 front axles are longer than ST185/165 items. Splines are the same.

Rears I am unsure about. Can check tomorrow.

[Anth_555]

from what i been told the st205 run a wider wheelbase then st185 , with longer drive shafts are you using celica hubs or mazda hubs?

[Malcolm]

from what i been told the st205 run a wider wheelbase then st185 , with longer drive shafts are you using celica hubs or mazda hubs?

wheelbase = length, track = width
just fyi...

[Anth_555]

correction track is wider

[sergei]

Good info you guys, thanks.

For axles, ST185 and ST205, I heard that they're interchangeable in a ST185 gearbox. I haven't found anything about the hubs, do the hubs from both generations accept the same diameter + spline count axle?

ST205 front axles are longer than ST185/165 items. Splines are the same.

Rears I am unsure about. Can check tomorrow.

I have both ST165 and ST205, and ST165 has way fatter front axles (roughly by 30%).
Also You cannot use ST205 axles in ST165 due to wider track.

The gearboxes and diffs are interchangeable. Make sure you get LSD diff (preface lift ST165 and some export ST185 didn't come with LSD).

[angryface]

This is what we do to swap the GT4 driveline into the 4WD Familias/323s

Celica 4WD (st165/st185/st205) transmission
Order/fab Mazda engine/Toyota transmission adapter plate
Slightly modify the transmission housing to accept the Mazda starter
Toyota gear shifting assembly
Fab new transmission mounts
Use the Mazda flywheel
Mazda clutch modified to fit the Toyota spline
Toyota clutch master/slave
Mazda hubs all around (Toyota outer splines fit like a glove)
Toyota front axles, unmodified
Toyota rear axles, 1" spacer between rear LSD & axles
Toyota propshaft
Toyota rear differential
Modified Mazda rear differential brackets, or modified Toyota differential bracks (less popular)
Notched oil pan to clear the center differential

To my knowledge, nobody has tried to swap st205 bits into the GT-R. I'm researching track widths to see how big of a difference it is, don't want to deal with binding cv joints and custom axles if I don't have to.

I have a hunch that st205 axles in the front would cause a problem, not sure about the rears, might not need to use the spacers with st205s in the rear... I'll try to get some dimensions... anyways, I ended up finding a complete driveline + shifters + clutch master for $200... talk about a real steal!

[angryface]

Just so you guys get an idea of why we do this... here's a comparison pic of the two gearboxes...

[fangsport]

is this road or rally use??
this is quite a common alternative to using the $pendy X-trac unit in Europe .
unsure how many dead GTX/GT-R boxes i have seen due to there weak casings causing the gears to climb out of mesh.

[angryface]

is this road or rally use??
this is quite a common alternative to using the $pendy X-trac unit in Europe .
unsure how many dead GTX/GT-R boxes i have seen due to there weak casings causing the gears to climb out of mesh.

It'll be for rally use, but it also needs to remain street legal as some portions are on public roads and rally here is still a minor sport with little governmental support. I also needs to multipurpose as a street car for a few days at a time, when I'm working in the hills. The engine will be powered by a GT28 and a GT35/40 in a compound setup, so there will hardly be any lag and I will be in boost at the 2k RPM mark and up ^.^

[frost]

[quote]GT28 and a GT35/40 in a compound setup[quote]

holy crap that is madness,
so the gt35 blows through the gt28 and then feeds the engine correct?
are you going to intercool the charge between the turbos or after the two turbos? or both,

i would love to see some pictures when you finish this set up,

[angryface]

so the gt35 blows through the gt28 and then feeds the engine correct?
are you going to intercool the charge between the turbos or after the two turbos? or both

Correct, the outlet of the GT35/40 feeds into the inlet of the GT28r, which multiplies the incoming pressurized air. I plan to run a single intercooler between the GT28r and the engine.