The T50 transmission in our AE86 was making some whining noises and had stiff and crunchy shifting. Being 40 years old, it probably needed some rebuilding. The trouble is T50 parts are no longer in production and getting genuine Toyota parts to rebuild it would be difficult and expensive.
The T50 ratios are considered to be kinda wide for the high revving low torque 4AG engine and your typical close ratio gear sets have pretty high 2.9 first gears and 1:1 fifths that scream the engine and limit the top speed. There are other somewhat weird close ratio options like the 3.5 cross-gear set where the 5th gear is a gear in between 3rd and 4th.
We decided that we wanted something more practical and a modern still in production transmission with plenty of OEM parts still available. This was the six-speed Asin J160 transmission as found in the FR-S/BRZ, RX8, S15 and MX5. For our car we got the version from a 3SG BEAMS version of the Altezza or IS. We chose this version because it is readily available on the used market. We got our transmission used on eBay for just under $800 shipped.
The transmission ratios for both transmissions are as follows.
T50- 1st 3.587, 2nd 2.022, 3rd 1.384, 4th 1.00, 5th 0.861
J160- 1st 3.874, 2nd 2.175, 3rd 1.484, 4th 1.223, 5th 1.00, 6th 0.869
The J160 gets rid of the infamous 3rd-4th AE86 bog out. Note that 2nd, 3rd, 4th, and 5th are all the gears you would probably typically use on the track and that they are all quite close. Something we did was to get a 0.767 6th gear from an S15 so we could run a lower final drive for better acceleration but still have good top-end speed.
The J160 can handle about 300 ft/lbs of torque and although it has a reputation for being weak in the S chassis and FR-S/BRZ, FT86, GR86, there is no way our little NA 4AG will ever even come close to this. It is still probably twice as strong as the T50 and best of all the parts are plentiful as the transmission is still in production!
Our transmission was a little crusty looking and had about 60k miles on it but when we took it apart it was in great shape internally. To reduce friction and make our transmission slick shifting we WPC treated all of the transmission internals, gears, shafts, sliders, shift forks, and shift rods, all got the WPC treatment. Then Izumi from WPC recommended we treat the syncros. We didn’t think this was a good idea because we thought synchros had to grip but Izumi said this would improve shifting so we ended up treating the synchros and balk rings as well.
To clean up the outside of the transmission we took the case to Mountune and had them vapor hone the exterior which restored the case to a better-than-new stain shine. Man, the more we vapor hone stuff the more we are addicted to the process. Check out this video on how it is done.
SQ Engineering sells this adaptor kit which allows the BEAMS J160 to bolt up to the 4AG and fit into the AE86. It comes with all the hardware and everything. We did not show all of the little nuts and bolts but the kit is quite complete. The kit also comes with a transmission mount and spacers to better fit different chassis.
SQ Engineering also sells a shifter relocation kit so the shifter can come up right in the same place on the AE86.
14 comments
Open lug nuts in Southern California on an AE86…Mike you’re braver than I am!
Are all J160 gears compatible with each other? I have an NC with the J160 which also has an absolutely horrible bog on the 3-4 shift… can I mix and match ratios out of all the cars they came in? Previously I’ve only been looking at NC’s and RX-8’s… but will gears from the 86 twins and S15 work too? And aftermarket gears designed for those transmissions? I know this might be a “duh” question, but I’m having a pinch me moment about it… might finally be able to get gearing I like!
Also, are these transmissions really good for 300 ft/lbs of torque? seams a little ambitious, no? Reason I’m asking is I’ve been toying with the idea of putting a Honda J series V6 into an RX-8 but the transmissions grenading itself with “crazy V6 power” has been one of the discouraging factors… How much torque would you realistically trust to this transmission for a street car with a decent amount of track use?
From messing around with S chassis cars and the FR-S it seems like the 300 ft/lb thing is about true, Once you exceed that kaboom. at least on track driven cars. On cars like our supercharged FR-S, the transmission seemed happy and reliable at 250 ft/lbs.
We exchanged 6th gear with an S15 one so the other gears can probably change. This one Australian company has a reliability mod for the box. We never had this chipping problem, more like 3-4 loosing the teeth,
https://neatgearboxes.wordpress.com/2014/04/16/nissan-silvia-s15-6-speed-gearbox-circlip-mod/
We’re talking crank torque, not torque at the wheels, correct?
more gear ratios to play with potentially makes things more interesting… time to spend hours looking up all the ratios and mix and matching them to find the perfect spread, haha..
Thanks for the link! Did you chip the teeth with the 250tq FR-S?
Hope you meant NB – the NC and later RX-8s are an inhouse Mazda top loading transmission.
There’s some variations, I think the NB has smaller diameter shafts, certainly a different size output shaft. At some point I’m going to get ahold of a Subaru version and see how much can interchange between them.
From many sources:
Vehicles that use the J160
Toyota Altezza AS200 and RS200
Mazda MX-5 (Miata)
Nissan Silvia
Mazda RX-8
Lexus IS
Toyota 86/Scion FR-S/Subaru BRZ
Correct; but only the 1999-2005 (NB) Miatas and the 2004-2008 RX-8 used the Aisin AZ6/J160 gearbox. The 2006-2015 MX-5 (NC) and 2009-2011 RX-8 used a completely different transmission for whatever reason; if you look up photos the differences aren’t subtle. More subtly though, while the Miata and RX-8 Aisin gearbox casings bolt to one another, the Miata version has some dimension differences on the output shaft and yoke. I don’t know if the Miata version is an oddball or if they’re all subtly different on internals.
Good to know!
well thats a shame… but thanks for the detailed info Dani!
Any chance you know if the 09+ RX8 transmissions can handle more power over the earlier Asin units?
Supposedly the NC transmission holds more power than the Aisin transmission; they used it again for the Fiat 124 Spider and they have a better reputation for hard use than the Aisin transmission does. They all have the annoying 4th gear ratio though; I think the Fiat 124 just has a different input to countershaft gear pair than the NC and RX-8 as the 3/4 gear ratio split is identical.
For the record, I’m coming from all of this from wanting to put an RX-8 front case on a Subaru version of the trans to get rid of that 4th gear (and a closer ratio 6th for track use) behind an NA 13B.
There’s a version of the RX8 in the UK (think 09+) that has a taller 3rd gear (1.536) which helps quite a bit with the 3-4 spacing. There’s a guy over on the Miata forum that did it and says the difference is huge. You do end up with a little bit longish 3rd, my IMHO thats easier to overcome being a lower hear and lower speed. With the long 4th and all of the wild 150whp my NC had it was starting to hit the aero wall right around the time you bogged into 4th gear.
I plotted out all the ratios, and I think my ideal would be the long 3rd paired with the 86 4th gear. If that was a thing… which its not…
What are the ratios for these transmissions?
US NC MX-5 and S2 RX-8 (the Mazda inhouse gearbox) are 3.815, 2.260, 1.640, 1.117, 1, 0.843. The US NB Miata with the Aisin box is 3.76, 2.269, 1.645, 1.257, 1, 0.843 and the S1 RX-8 with the Aisin is the same except that 4th gear is 1.187:1. I have no idea why.
I’m seeing the UK NC MX-5 having 3.709, 2.190, 1.536, 1.177, 1 and 0.832 which, yeah, seems a little better. It looks like the JDM NC had the same ratios as the US ones.
That is a pretty big jump!