The BRZ / FR-S / GT 86 transmissions and driveline: what we know so far

Although the Toyota GT 86 (or, simply, 86) / Scion FR-S / Subaru BRZ triplets have finally been revealed, there still remain a number of half-answered or unanswered questions, such as North America pricing and precise curb weights, Scion equipment levels and detailed driveline information, such as which Aisin manual and automatic transmissions and Torsen limited-slip differential the sports coupes will use.

First, though, some background on Aisin, which has been widely acknowledged as the production FT-86 variants’ transmission supplier. Aisin, which is over 30% owned by Toyota, is an integral part of the carmaker’s vertically-integrated keiretsu group of companies with interlocking business relationships and shareholdings. Indeed, a vast majority of Toyota vehicles use an Aisin transmission or transaxle, even including the mighty Lexus LFA. Quite notably, the parent Aisin Seiki Company has separate divisions (and even individual websites) for manual transmissions (Aisin AI) and automatic transmissions (Aisin AW). In spite of Toyota’s historic dominant role in Aisin transmission usage, however, the latter has grown and branched out to supply virtually every major carmaker on the planet. This makes for some mighty unexpected transmission-sharing bedfellows, as you’ll read further on.

The manual transmission: Aisin’s AZ6
Since the demise of the 1st-generation Lexus IS manual transmissions in 2005, Toyota’s sole remaining shift-it-yourself tranny for longitudinal rear-wheel-drive and RWD-centric all-wheel-drive applications for cars and light trucks has been the 6-speed Aisin AY6, which, in Toyotaspeak, is the RA60 series of transmissions. It actually exists in a plethora of versions, with varying individual and differential gear ratios. The RA60 proper is used on current 2-wheel-drive Toyota Tacoma pickups, the beefed-up RA60F for 4-wheel-drive Tacomas, RA61F for 4-wheel-drive FJ Cruiser, RA62 for the Lexus IS 250 and RA63 for Europe’s Lexus IS 200d and IS 220d diesels. The Aisin AY6 is also used by General Motors in V6 manual versions of the Cadillac CTS, reborn Chevrolet Camaro and Australia’s Holden Commodore. With the AY6 receiving generally tepid reviews for its vague and rubbery shifter feel in both its Toyota/Lexus and GM applications (including yours truly’s thoughts on the Lexus IS 250C Manual), this author dreaded the possibility that this might be the leading row-your-own contender for putting the power down to the rear wheels of the FT-86 family of coupes.

Fortunately, Aisin also makes a far more appealing manual option: the AZ6 6-speed. Notably absent from the Aisin AI website’s FR (front engine, rear-wheel drive) transmission page, Internet research (including Wikipedia) reveals a veritable cornucopia of vehicles that use the AZ6: Honda S2000, Mazda RX-8, 2nd-gen (NB) Mazda MX-5 Miata, the final S15 Nissan Silvia Spec-R… and the Toyota Altezza/Lexus IS 200!

So, which Aisin 6-speed manual would BRZ, FR-S and (GT) 86 use? AY6 or AZ6? This author certainly wasn’t alone in wondering. Members of ft86club were asking this very question as far back as March 2010! A stroll through the 2011 Tokyo Motor Show produced the “smoking gun” you see above, brought to us courtesy of the response.jp website.

Bear in mind, however, that the Aisin AZ6 is but the basic “framework” or “structure” for the transmission. Each carmaker is able to tweak and tune such parameters as individual gear ratios, transmission cases, internal architecture, drive shaft coupling, clutch actuation and even shift “feel”. The fiercely independent, go-it-alone Honda, in particular, is understood to have widely modified its take on AZ6 for its S2000 sports car. The carmaker, which develops its own widely-praised transaxles, saw the need to swallow its pride and turn to archrival Toyota’s keiretsu for its first front engine/rear-wheel-drive transmission in decades in order to meet S2000’s cost targets.

Toyota and Subaru enginers also tweaked the AZ6 for the “Toyobaru” sports coupe, shown above, with Christie Schweinsberg of WardsAuto reporting that “The (manual) is 80% changed…to maximize shift feel”. Club4AG webmaster, administrator and events coordinator Motohide Miwa was fortunate enough to drive one of the Scion FR-S pre-production prototypes, and shared these impressions on the Club Lexus forums:

The shell case and most of the mechanical elements seem similar to the Altezza, S15 transmission, however clearly there are guides and larger gear teeth than the previous units. From what I felt in the short drive in the FR-S, though, is that the issue of 3rd gear being slightly sloppy to throw in quickly has been eliminated and that the new transmission feels firm and smooth into each gear when nice and warm. I have high expectations for this gearbox as well as the all-new Torsen LSD equipped differential box. (at least from comparison with AE86, everything is much bigger and smoother…and it looks to handle whatever duty cycle a tuner has for this light car…)

I see nice deep splines on the output shaft too…

IS/Altezza feels similar, I suppose, but it always felt a but clumsy going into 3rd when warm, but overall it was great.

This FR-S unit feels quicker to shift, throw is very short and positive, and just feels like it wants to run through each gear on a raceway… (I haven’t done that yet, but I will let you know if I ever get a chance. So far everyone who DID drive says it’s glass smooth and precise, easy to operate.)

Perhaps what I wanted to say is that it feels like the best attributes of all Toyota RWD transmissions converged to make this one feel better than ever.

For those of you who are looking forward to turbo or supercharge your BRZ / FR-S / GT 86 via the aftermarket, however, we must remind you of a crucial caveat that appears on the second photo of this article: “Medium Torque Capacity RWD 6-Speed Manual transmission (AZ6)”. A cursory glance at all the vehicles that have used the Aisin AZ6 reveals that the torquiest of the lot is the S15 Nissan Silvia Spec-R, producing 202 lb/ft. All other AZ6 users produced somewhere between 124 and 163 lb/ft of torque, with stock BRZ / FR-S / GT 86 rated at 151 lb/ft. Notably, when the North American market demanded a manual transmission option for the Lexus IS 300 and its 2JZ-GE 3-liter inline 6’s 218 lb/ft of torque, the Aisin AZ6 (or J160 in Toyotaspeak) was deemed to be too weak. Instead, a W55 variant of the W58 5-speed manual from the naturally-aspirated Toyota Supra and Lexus SC 300 was used. Thus, it’ll be quite interesting to see what Subaru and Toyota engineers would do for a possible future manual supercharged or turbocharged FT-86 variant. Further modifying the existing AZ6? Or doing so with the higher-capacity AY6 (which can reportedly handle over 345 lb/ft of torque)? Or reach out to Getrag as Toyota did for the 233/V160 when it needed a stout yet sporting 6-speed manual for the Mk4 Supra Twin Turbo?

Also of interest is what designation Toyota will give to the Aisin AZ6 manual as applied to the Toyota (GT) 86 and Scion FR-S. We concur with Jeff Lange’s suggestion of J161.

The automatic transmission: a trio of Aisin possibilities, with one the likeliest
In stark contrast to the manual transmission situation, answers are more nebulous and speculative when it comes to determining which precise Aisin 6-speed automatic is used by the BRZ / FR-S / GT-86 triplets. And three is indeed the operative number here, for a trio of possibilities emerge in this author’s eye.

Most reports claim that “a 6-speed version of the IS F automatic” would be used in 2-pedal versions of the Toyobaru sports coupes. This would be a Toyota AA80E (or Aisin TL-80SN) 8-speed automatic morphed into an AA60E / TL-60SN 6-speed. These reports claim as evidence Part 2 of the 27 November 2011 Presentation by TMC Chief Engineer Tetsuya Tada and the translator’s comment around the 1:40 mark. This would mean that the GT 86 / FR-S / BRZ automatic would be one of the most responsive automatics in the world, with a lock-up torque converter in 2nd thru top gears and downshift rev-matching. Fantastic as that would be, color this author deeply skeptical, for the AA80E-to-AA60E changeover is not just a matter of removing 7th and 8th gears. Merely doing so would leave a top direct 1:000 6th gear, with no overdrive top gear for more relaxed highway cruising and better fuel economy, and would fly in the face of current Toyota/Lexus practice of a direct 1:000 4th gear and overdrive 5th and 6th gears for its 6-speed automatics. Thus, all individual gear ratios would have to be revised. Would Toyota go to all this trouble when it already offers a couple of more viable and less expensive Aisin automatic alternatives in other Lexus models? We think not.

For the 4th-generation Lexus GS 350 just reaching U.S. dealer showrooms, the A760E high torque capacity 6-speed automatic has received a number of welcome tweaks versus the previous GS and current IS 350, such as earlier torque converter lockup, faster upshift and downshift times and throttle blips accompanying downshifts, thus going a long way towards granting this author’s wish list from 2009.

But why use the A760E when the less powerful and less torquey rear-wheel-drive Lexus IS 250’s A960E 6-speed automatic is roughly 40 lbs lighter? And this, precisely, is what Toyota and Subaru seem to have done, for a comparison of Toyota Japan’s official 86 site’s Spec page and the Lexus IS 250/350 Product Information PDF document from the Lexus USA Newsroom reveals that 86 and IS 250 automatics share identical individual gear ratios of 1st 3.538 / 2nd 2.060 / 3rd 1.404 / 4th 1.000 / 5th 0.713 / 6th 0.582 / Reverse 3.168. Not a “smoking gun” in the manner of the Aisin AZ6 manual photo you saw earlier, perhaps, but very strong circumstantial evidence, nonetheless. Notably, though, the differential (or final drive) ratio for Japan’s Toyota 86 is the lower (numerically higher) 4.100 from all-wheel-drive Lexus IS variants (presumably for better low-end acceleration), as opposed to the RWD IS 250 Automatic’s 3.909. Best of all, numerous reports and early reviews suggest that the upgrades to the beefier A760E (earlier torque converter lockup, faster upshift and downshift times and throttle blips accompanying downshifts) have also found their way to the lighter A960E as applied to GT 86, FR-S and BRZ.

The limited-slip differential: Torsen’s T-2/Type B
Although a number of automotive suppliers, such as OS Giken, Eaton and Quaife offer limited-slip differentials, the name most associated with this valuable handling and performance helper is Torsen. Based on Vernon Gleasman’s pioneering work on the Dual-Drive Differential he invented in 1958, this Torque-Sensing (hence the name) limited-slip differential’s manufacturer has changed hands and corporate overlords a few times. The official Torsen site’s home page’s History Brief section summarizes the boardroom gyrations, but it was this passage that caught our eye:

Toyoda Machine Works Ltd., in 2003, purchased the worldwide Torsen division from Robert Bosch / Zexel Corporation. Zexel Torsen, Inc. was then renamed Toyoda-Koki Automotive Torsen North America Inc. to reflect this change. The company name change became effective on September 1, 2003.

Koyo Bearing Corporation merged with Toyoda Machine Works and formed JTEKT.

Thus, Torsen, like Aisin, is an integral part of Toyota’s keiretsu group of companies with interlocking shareholdings. Given this fact, it’s mildly surprising that the carmaker has made relatively little use of Torsen’s limited-slip differential in production Toyota, Lexus and Scion models. For one thing, none of the company’s numerous front-wheel-drive offerings have followed Alfa Romeo, Ford, Honda and Nissan’s lead in using LSD with FWD in their performance models from the factory, even though TRD does offer a FWD-compatible unit in its accessory catalog. (What performance FWD models does Toyota offer, anyway, many will rightly ask?) In fact, Torsen’s OEM Applications – Worldwide PDF document only lists recent all-wheel-drive Lexus (GX, LX and AWD versions of LS, GS and, presumably, IS) and Toyota (4Runner, FJ Cruiser and sundry Land Cruiser variants) models as using a T-3 (Type C) planetary type differential; and Lexus’ LFA supercar and post-2010 IS F as using a more rear-wheel-drive appropriate T-2 (Type B) unit. The contemporary Torsen applications listed there, however, ignore not only the upcoming Subaru BRZ, Scion FR-S and Toyota (GT) 86, but historical enthusiast models such as Toyota Altezza/1st-generation Lexus IS, Mk III and IV iterations of Toyota Supra and numerous Japanese Domestic market platform-mates of these much-beloved vehicles.

The T-2 (or Type 2 or Type B) denomination, however, simply informs us, in broad terms, that the Toyobaru triplets use a rear limited-slip differential with a parallel gear arrangement. Beyond that, a number of variables come into play, such as the differential gear ratio, the number of teeth in the drive pinion and ring gear, and the ring gear size. As we learn from an overseas 1st-generation Lexus IS Differential information page from a technical/training manual, these emerge as notable differences between the IS 200’s F19TX limited-slip differential and the torquier IS 300’s F20TX unit. While both use a 43-tooth ring gear, the F20TX gains an extra pinion tooth (12 versus 11) and, most crucially, the ring gear size is 190mm (7.48″) for the F19TX and 205mm (8.07″) for the F20TX. A third possibility (again?!) is the 2010-and-newer Lexus IS F’s FD21AT unit, but we’d rule that one out quickly, given that it would probably be overkill for a car with half the power.

Further informed, intelligent discussion on this subject comes to us from an ft86club thread titled Confirmed Torsen Differential.

Photo Credits:
Photo 1: Official Toyota Japan 86 site
Photo 2: Response.jp
Photos 3-5 and 7: Keishin Tamashiro
Photo 6: Scion USA Newsroom