What is the lowest possible gearing that I can have with turbo differential? I have read that 929 uses same internals and they can be swapped into turbo diff. But from what I found lowest ratio is 3.7. Maybe there are some other options that would give me even lower ratio?
If I can't find anything lower I will need to use non-mazda diff, but before I do that I want to consider all options with retaining stock diff.

P.s. it's for piston engine and short gearbox.

 

Nothing else has the same long pinion gear the FCs use. So i think the answer is a 3.9...

You're better off using a ford explorer diff.
http://www.roninspeedworks.net/index...&product_id=70

 

3.7 is the tallest mazda has made

 

Thanks for the info, ditching mazda diff seems to be the only option then

 

Just out of curiosity, which FC model came with a 3.909 TII Diff? I'm pretty sure that all Japan-Spec FCs with Automatics were 4.10 with a part number prefix of P012. 4.30 TII gears, such as those found on the Infini IV, are P072.

What cars were equipped with this differential gearing? Now you got me curious!

 

Sorry for resurrecting old thread but I am still trying to find an option. Maybe someone can give more input on 3.7 differential? This gear ratio could work for me. Also maybe there are any other bolt on options rather than pretty expensive Ford Explorer kit http://www.roninspeedworks.net/index...&product_id=70?

 

3.727 in RWD B2600i's
Mazda Differentials - Mazdatruckin.com

 

by the by, this is correct, the Japan spec T2's were all 4.10, manual or auto. additionally, i have an S5 brochure and the GT-X is the only model to come with limited slip. the GT-R, and GT-limiteds were open.

 

Not FC. I think its the automagic FD diff that has a 3.9 ring gear and it fits the FC. I could be wrong though.

 

The short pinion of the FD wont fit into the FC long pinion third member setup though. And the 4.1 pinion(fc) wont work with a 3.9 ring gear(FD).

 

With an Explorer diff you can run from a 2.73 to a 5.38.

 

I thought about doing an explorer differential even on a NA RX-7 (Not like Orangefonts NA ).

Getting a custom set of gears done for the FC costs about $1100 from Mazdatrix, Swapping in a explorer diferential has more integrity then the Mazda one, without the Mazda price tags for everything. Plus it can be setup by any shop without any experience with that sort of thing.

I couldn't find anything for the NA rear end that would be reasonable, or a GTUs differential (only so much added gearing) for a price that was also reasonable.

Anyhow, good luck!

 

this is backwards, most rear end shops can setup Ford rear ends with their eyes closed because they do it all day, every day. Ford's build quality is terrible, and they sell a lot of them. even at a Mazda dealership in the 90's we had a guy who spent a day a week building the ford diffs under warranty.

they don't break, but they are loud and sloppy.

 

Has anyone tried having a machine shop switch the gear on the pinion? I know this can be done, if there is anyone still alive that has the skills.

Long ago in an earlier life I had a machine shop switch a pinion gear from a short shaft to a longer shaft to fit a specific rear end in a

-wait for it-


1950 Chevy Pickup.

 

You forgot cheap. They are no louder than a Mazda diff honestly. The key is to use Ford gears if possible. They are quieter than aftermarket gears.

The Mazda diff setup is pretty straight forward actually. Very similar to a Ford 9 inch, so most rear end shops should not have an issue setting one up. The only hard part of the 8.8 setup is pinion preload. If you screw it up you have to pull the pinion and start over with a new crush sleeve.

As an FYI - the Ford 8.8 conversion ends up the same weight as the T2 diff and halfshafts.

 

i'm not saying they don't work, they do, i'm just saying everyone knows how to set em up because they have had to a lot

 

Its tempting, i could get an exploder diff with 4.56 gear in the Tii for what it would cost to have one made for the Tii 8" casing. Sadly I have a new Carbonetic diff I don't wanna waste :/

 

That sounds like throwing good money after bad.

You could do a Ford 8.8 with 4.56 and Detroit Locker for a 2 way diff if you want to drift, or like an Auburn pro if you wanted a 1.5 way LSD.

 

Whoa Cowboy.

I was talking about the Exploder rear end, not the Mazda ones. Sorry if I wasn't specific.

 

Mr. O, Font,

How much did your explorer set up cost you in the end?

 

About $2100, but I did an aftermarket diff and a full rebuild. The only parts reused were the housing and gear set.

That includes the conversion kit ($1200), Explorer diff and half shafts ($300), full rebuild kit ($70), solid pinion spacer ($20), Detroit Truetrac diff ($450), and setup at a rear end shop ($100).

If you want gears other than 3.55 or 3.73, add $140 to that for a set of Ford gears, less if you can find them used. You can sell the gears out of your diff if you don't need them. I wanted a helical style diff and 3.73 gears so I bought a 3.73 open Explorer 8.8 and then put in the diff I wanted. You can find the 02-05 Explorer diffs with clutch LSDs in them, that will save you some money. A standard Ford Trac Lok LSD is $219 shipped. A Trac Lok rebuild kit with carbon clutches is $120.

It is cheaper than an aftermarket diff, one off gear set, and a rebuild of your TII diff.

 

Where did you get yours setup for $100? Everywhere around here wants 4 hours ($350) to do it...

I had an easier time getting my t2 diff built...

 

4 hours???

I dropped it all off at a rear end shop that also does race car rear ends. They even asked if I wanted to wait around because it would be done in 2 hours. I just picked it up the next day.

Pro tip: all the Ford gears should require the same length pinion sleeve as whatever you pull out of the diff.