Jeff's 323 GTX

[BFMRGTX]

I used to know the answer to this, but is the GTR rear diff a viscous unit or clutch-type? Memory seems to recall it being a VLSD, but I think that it wasn't usable with the BF pumpkin? I forget / don't care enough.

[trailrider098]

Bf and bg use the same rear diff casing. The GTR diff is a Viscious LSD and can be put in a bf case. Im using a stock miata Torson LSD in the back of my protege 4wd and know those will swap too

[Scott@USRT]

added some a few mods, s10 front dam, rocketman chip, some Recaro seats and a GTR rear diff., Tenzo-R DC6 16'' wheels

You stuffed a GTR (BG chassis?) rear diff in the stock BFMR rear housing?

Fiberglass rear hatch (not yet installed)

Where'd you find this piece?

Triangle skirts (will replace USDM when the car is painted)

Blasphemy! NADM skirts for the WIN!

GTAe hood hump

EPIC

[sprint45]

Nice build so far. Where did you find the GTR replica front bumper? I noticed you had the GTAe front bumper as well. Which one are you going to use? I would definitely be interested if you ever wanted to sell it.

[trailrider098]

Nice build so far. Where did you find the GTR replica front bumper? I noticed you had the GTAe front bumper as well. Which one are you going to use? I would definitely be interested if you ever wanted to sell it.

Corksport sold the GTR replica for a BF chassis, im using the GTAe one now but the GTR replica will stay in my attic as part of the "collection".

Scott, Im using a complete GTR rear diff and housing/case. the case is the same as a BF chassis GTX, just a lsd diff. The rear hatch was from a group buy about 7 years ago. Aperently only one person in the US bought 2 of them and he finally sold me the extra one. The triangle skirts will be added when i do all my body work since they attach to the car via plastic clips which require holes on the rear quarter panels. GTAe hood hump was pre-facelift gtx stuff and i love it


Now if Terry could just sell me that rear plate support piece he has layin around so i can complete my master plan/the back of my car........

[Scott@USRT]

Scott, Im using a complete GTR rear diff and housing/case. the case is the same as a BF chassis GTX, just a lsd diff.

Okay, school me, please. I know of the Miata viscous (weak) rear LSD, the Mazda MS unit (made by... Cusco iirc?), and... nothing else that fits the BF rear housing. Then there's the Miata Torsen-type which comes from the BP-powered cars and that's too big to fit the BF/early Miata housing. So, which unit is this "GTR" piece that you've used? Where does it come from?

Thanks for the other answers, too.

GTAe hood hump was pre-facelift gtx stuff and i love it

Oh, it's total sex. I'm going to do it one of these days! Btw, what's the weight difference between the CF hood and the OEM steel piece?

[evohunter323]

Nice hood.

[Scott@USRT]

hold up a sec...

Scott, Im using a complete GTR rear diff and housing/case. the case is the same as a BF chassis GTX, just a lsd diff.

So... the BG GTR rear diff is the same piece as the VLSD from the early Miata? If not, then what's the difference?

Im using a stock miata Torson LSD in the back of my protege 4wd and know those will swap too

Mmmm... something smells fishy here. Yes, the Miata Torsen diff fits a BG without any issue. There's sufficient room back there. However, have you (or for that matter "has ANYbody") EVER seen a Miata Torsen-type rear diff installed in the rear of a BFMR? I have not. I've also read for years that they're not compatible given the amount of room in the rear of our early cars.

Edit: This just popped up from Bob Bundy on the Yahoo!groups GTX list:
"Torsens wont fit they are larger 1.8l miata size unless you get serious with some custom mounting of a different carrier assembly. 1.6l miata VLSD or a mazda comp clutch type bolt into the GTX housing. Need to re-use the ring and pinion from the GTX to keep the 3.909 ratio."

Yeah... I think a lil' bit more explanation would be a good thing, Jeff.

Anyway, this brings to mind my internal debate about viscous LSDs vs Torsen/helical gear-type vs. clutch-type. Each has benefits and compromises: In the rear, a clutch-type is superior for rally competition. However, it's a bit jerky in operation (and they require maintenance over time). The Torsen variant is super-smooth but only works when both tires have *at least some* grip. This makes it fairly inconsistent on loose surfaces and occasionally completely useless (still WAY better than open, though). Finally, viscous is as smooth as Torsen and consistently delivers torque to the proper wheel. However, it is also reactive by nature requiring slip to exist before it can step in and correct anything. Folks consider them "weak" in effect as a result.

FWIW, If I had my "druthers" I'd have a Torsen up front, moderately stiff viscous in the middle, and clutch-type out back. That's with a 10 -15% gear torque bias to the rear, of course. I'm eyeballing the BG AWD system and also the DSM setup (along with 4G63).

Cheers,

P.S. Sorry if this fixation of mine on diffs = a thread hijack! It seems to be related enough to your build to keep it goin' but state any difference of opinion if you have it, please!

[BFMRGTX]

Happy Reading, lots of good info here:

http://autos.groups.yahoo.com/group/323gtx/message/37425

http://autos.groups.yahoo.com/group/323gtx/message/32681

http://autos.groups.yahoo.com/group/323gtx/message/33167

http://autos.groups.yahoo.com/group/323gtx/message/32934

http://autos.groups.yahoo.com/group/323gtx/message/33160

http://autos.groups.yahoo.com/group/323gtx/message/26854

[trailrider098]

I'm posting from my phone now but Ill edit this tonight, I have pics on the computer from the rear diff install on the protege diff. I was pretty sure it was a torson diff but i did buy it from a local miata guy so maybe it was just the miata viscious diff.

And yes, the Mazda Gtr rear LSD is the same as a miata viscous LSD. You are also correct, the 7inch gear from a BP miata will not fit into a 6inch Gtx/gtr/b6 miata rear differential case. I always thought there was a factory option for torson or viscous rear LSD's on the miata.

[Scott@USRT]

I always thought there was a factory option for torson or viscous rear LSD's on the miata.

Yeah, there are. The viscous is what you and I both have installed and the Torsen doesn't fit our cars as you've accurately described. The BFMR just doesn't have enough room but the Miata rear assembly does. So, anything fits in the Miata but only the viscous LSD works for us. Well... that unit, the clutch-type, and obviously the stocker.

P.S. Thanks for the great links, BFMRGTX.

[trailrider098]

So i bought the rear lsd from a 1.6L miata, owner claimed it to be the torson lsd. i took the diff out of the miata case, open diff out of the protege case, swaped ring gears and reasembled(basicly). what i meant in my last post was that i thought torson and viscious lsd's were availabe for the 1.6, i know differentials for the 1.8 were an inch to big for our case

left pic is the lsd i installed in my protege, help please if anyone can tell if its torson or viscious
on the right is the slightly bigger 1.6L miata ring gear vs. our gtx/gtr/pro 4wd gear

[NoBoDy_nz]

Nice Build, where did you get the CF bonnet from?? i want one so bad to finish the look of my car off, are you still able to get them ?

[Scott@USRT]

Nice Build, where did you get the CF bonnet from?? i want one so bad to finish the look of my car off, are you still able to get them ?

Uh oh... You went "there". There was a notoriously horrific group buy on the Yahoo!Groups GTX list several years ago. There was fraud involved, a burnt down fab shop, lots of unhappy customers who pre-paid... Yeah, it was a big time sh*t show.

[BFMRGTX]

Ohhhhhh, that is a long, sad story.