'95 4.1 gears in '01 diff

[JackF]

Hey guys,

I'm looking at upgrading the diff in my NB8B (open 3.63), currently looking at getting a Kaaz clutch pack centre, but I also want to change ratios. I've found a 4.1 ring and pinion gearset from a '95 NA diff, and just wanted to double check with anyone who might know if it would be fine to put in my '01 diff?

I'm not too knowledgeable on NA diffs, but am I right in saying that all 1.8 diffs are essentially the same? I've heard bad things about the 1.6 diffs, does any of this weakness extend to the NA8 diffs, or did they basically fix them by going to the 7" size?

By the way, for anyone interested, Nengun have the Kaaz DBZ1810 for $923, which is the cheapest I've seen.
http://www.nengun.com/kaaz/basic-solid-lsd

Cheers,
Jack

[hks_kansei]

Yep, the 1.8s are the same, and the issue was fixed by going to the 7in ring gear.

So yeah, using a 1995 4.1 will be fine.


The only freak diff of the lot was the SE, which used different axles to the rest of the MX5's (stronger fatter ones) and so they use a difference diff centre (but I think thye kept the same ring and pinion?)





Also, good on you for changing the ratio, the 3.6 diff was the worst thing Mazda did to the car.
Combined with the shorter ratios in the 6 speed it should feel pretty good. When my 5 speed goes boom I'm looking to stick a 6 speed in mine for the same reason.

[ryuhou]

if its for a road car i find 3.9 to be the best balance. Ive tried both currently running 3.9 t2 on an 03 - just my 2c
Cheers

[JackF]

hks_kansei - Thanks a lot, exactly the answer I was looking for

ryuhou - You're probably right, I can see how 3.9 gears would be slightly better for street use. Was it a significant difference between 4.1 and 3.9? Was the 4.1 particularly buzzy on freeways? It is a street car, but I don't really do freeway driving or get out of the city much, so I'm not *too* fussed by a extra few hundred RPM at cruising speed (although we'll see, I guess). There's also the fact that we only got the 3.9 ratio in the 10ae, which makes the finding the gears by themselves in Aus a bit of a hassle. Might have a look on yahoo Japan, or US ebay or something though, see if anything comes up.

Cheers guys

[hks_kansei]

Was it a significant difference between 4.1 and 3.9? Was the 4.1 particularly buzzy on freeways? It is a street car, but I don't really do freeway driving or get out of the city much, so I'm not *too* fussed by a extra few hundred RPM at cruising speed (although we'll see, I guess).

roughly a 4.9% difference between the two.

My 8A (with a 4.1 and a 5 speed) sits at about 3100rpm at 100kph from memory.

Take into account the different ratios of top gear for the 5/6 speeds and you sit at about 3200rpm.

go 5% lower for the 3.9 rear end and you get about 3050rpm


The ratios are here:
http://www.miata.net/garage/KnowYourCar/S8_Gears.html

so if you feel like it you can get out the calculator and work out the engine speed on the highway.

edit:
be aware that my calculations there are pretty rough, and rounded.
That, and I can't remember exactly what RPM mine sits on at 100, I just know it's right where my exhaust drones most (fun)

[ryuhou]

yeah the numbers dont tell the full story. big difference in my experience

[93_Clubman]

There's also the fact that we only got the 3.9 ratio in the 10ae, which makes the finding the gears by themselves in Aus a bit of a hassle.

Aust Domestic Market 10AE came with 3.6 ratio:
viewtopic.php?f=29&t=62562&p=784010&hilit=10AE#p784010