The 1998-2000 1.8iS and 1998-99 “Sport” (watch out for tarted up ordinary cars sold as a “Sport” special edition) had a 5-speed with a 4.1 final drive JTEKT/Zexel Torsen T2 differential. The problem is, 25 years on, cars have had so many wheel swaps etc, it becomes hard to tell a standard 1.8 from a 1.8iS, as the major visual addition was 15" wheels.
10AE and Icon (the early version, not “Icon 2”) came with a 6-speed box and a JTEKT/Zexel 3.909 final drive Torsen T2 differential.
All 1.8 manual Japanese imports of this period had the 6-speed box and a 3.909 final drive Torsen T2 differential. Many imports would have come in during 2005-2010, and may have a lot less rust. But they are most costly or harder to insure.
There is a source claiming all of the JDM NB 1.6 models had the JTEKT/Zexel 4.300 final drive T2 differential, making this the same ratio as the T1 diff in the NA RS-Limited, and exactly the same diff as the Phase 2 NA 1.8 in Japan. If that’s true, for hillclimbs, that the most desirable diff out of the scrapyard. But I don’t think this is correct.
Late on, the parts list DO show a 4.300 LSD ringset for the facelift NB. I think this is a spare part for the clubman spec NR-A, which was a track special 1.6, and the Web Roadsters.
The face lifted car came in during 2000. LSD was fitted to 6-speed models. The Japanese model in 2000 is listed with a 3.909 final drive LSD, which I believe would have been the unburstable Torsen T2 differential. However the UK December 2001 technical spec lists the Sport as having a 3.636 final drive. Note the UK car developed a lot less power 146PS @ 7000rpm versus a heady 160 PS @ 7000rpm. At the time, this created controversy because Mazda “accidently” used Japan numbers in US brochures, resulting in a law suit and Mazda compensating owners.
I’ve never noticed before, but the JDM 1.6s are also up on power, about the same as the Mk1 1.8. Anyone with a naturally aspirated 1.6 Mk1 with 125hp would have been pretty happy that the £1000 spent on Racing Beat intakes and exhausts paid off,
In Japan, they never adopted the 3.636 diff. The Mazdaspeed Turbo Roadster in Japan retained the 3.909 diff, but the US version had a 4.100 diff, reportedly a Hitachi built Torsen.
Some time in 2003, the differential switch from the JTEKT/Zexel/Hitachi Torsen differential to the notorious Tochigi Fuji Super Lsd, the same diff fitted to NCs. Some of these, at least for the owners who bothered to look, had lumps of clutch plate fall out with the oil. I woudln’t be surprised if there is a lot of these cars still with original differential oil in. No reports of anything bad happening, except that the diff might revert to being an open diff. That owners can’t tell might be telling about the true lock up ratios of these Torsens.
Whats the practical difference between a 3.9 and a 3.6 diff. The 3.6 diff car will be faster off the mark but pulling higher RPMs at motorway speeds, so noisier and thirstier. So the Japanese face lift cars will feel a lot quicker than the British equivalents. Plus less rust.
The 6 speed box isn’t just a 5 speed with an extra gear. The 6-speed is an Aisin AZ6 box also used in a number of Toyotas and Nissans. The earlier 5-speed was Mazda built, and during the NB lifespan, Mazda switched to Aisin for the 5-speed. Aisin 6-speeds are stronger boxes, but the original 5-speed isn’t really known for being weak.
Rare UK 1.8iS Sport (Autotrader), with the correct bodykit. Both arches have rotted. Typical histpry of rotted sills, front chassis leg rot. Interior ok. £2700.
Standard early NB UK interior
Standard early NB JDM interior
LSD part numbers for JDM NBs
NB1, NB2, NB3 (anything below NB8-4000000); MM03-27-200
NB4; MS01-27-200
NB4 Turbo; MM04-27-200B
Phase 2 T2 Torsen NA8: MM02-27-200A
Phase 1/ 1.5T1 Torsen NA8: MM01-27-200 (the RS and R limited had different final gear sets)
Personally, I would forget about looking for a car specifically with a LSD. Its always been the adage buy on condition not spec, and that’s never been truer but for the NB. There seem to be a extremely large number of tired and abused NBs on sale; many seem to have lead a harder life than the NAs. Or maybe all the really terrible NAs have gone.
A car with LSD is more likely to have been ragged. I also wouldn’t rule out a 1.6 NB; more likely to have a more careful owner. Yes, down on power, but the 1.8 s hardly a powerhouse. You can turbocharge the NB 1.6 if you want. The B6 is a revvier lump than the BP. The Japanese parts lists indicate that the final gear set on the open 4.3 diff is exactly the same as the 4.3 gear set listed for the LSD in th final NBs, suggesting you can use bits from a 1.6 diff to change a fuji 3.6 diff from a scrapped car to 4.3. Which is also interesting if you get one of the late 5 speed 1.8 special editions, which will have a 4.100 final drive.
