I pulled the blown transmission yesterday and was quite disappointed. I was expecting horrible things when I drained the fluid but all I got was nice looking oil and a few tiny chunks of metal. I'll disassemble the transmission later this week to see the real damage. I don't feel like working on it today, so the new transmission goes in on Monday.


I think I'm going to just email Kennedy Engineering since they make the 13B to T-5 adapters and ask them. I would assume they know for sure.

Finding non-RX-7 rotary cars around here is like finding an orifice on Paris Hilton that has not been violated. I think my Cosmo is probably the only non-7 rotary vehicle for 200KM in this area. So it would be rather easy to get a TII transmission, but an RX-4 unit would be significantly harder.

 

I've got a 4 speed out of an RX3 As a technician I enjoy seeing carange in transmissions and other components. It reveals the weak points of the component and it helps in future diagnosis of other vehicles.

 

From My experiences a T5 is a little shorter... but you can move the shifter easily

 

I had my TII unit cryo treated and it seems to be holding up to 550 HP fairly well. I stripped 3rd gear on my last TWO trannies though..

 

Back in the day we used to run OLD SCHOOL CELICA TRANNYS(the cast iron ones)on several horsepower 13B powered cars and held up a lot of abuse,I have a old friend that until this day still holds the ET drag record using a TURBO 2 TRANNY on his full chassis RX3 WEST RACING with a couple of mid 8 seconds passes and a handfull of low 9s so in my opinion T2s trannys are hella strong.

 

Hey aaron its ok, atleast you vcan always find another N/A tranny and for 1/3rd of the price of a t2 one,jajaj.

And if it breaks in another 2yrs you still come out on top.

 

The picture of the remote mounted shifter above is sort of exactly what I am trying to avoid. Remember, my car is not some stripped out track shell, it's a full interior daily-driver. I just replaced all the carpets and trip (including most of the dash trim) so I'm not really willing to cut massive holes in the floor and rework the shifter area.

I have nothing against the strength of the TII transmission at all. My issue with it is a philosophical one in that I cannot stand to have TII parts on the car. However if it turns out that the T-5 is going to be a major pain, it looks like a TII transmission is where I will go. Regardless, with the T-5 I need to use a TII bellhousing, starter, flywheel, clutch, slave and get a custom driveshaft. With the TII transmission I would need the exact same stuff but the shifter ends up in the same location and the cross member from the NA (all new...) bolts right on.

Tonight though, another NA unit goes in so I can take advantage of the great weather and drive the car.

 

Ouch Aaron, glad to see you didnt have to much downtime. When i read the thread title i thought it was your engine that blew, not your tranny. But what a sigh of relief. Wish you good luck with your next transmission swap. My vote is T-5

 

Well, at least it didn't end up like my buddy's Sentra SE-R tranny. It wouldn't shift into any gear anymore, so we proceeded to drain it. The oil had turned a bright and shiny silver with the consistency of a gritty paint.

 

I got a little sad when I saw this thread cause I thought your motor might have blown XD. Lets hope you can somehow get the T-5 In there, would suck to have to put something TII in there T_T

 

Used FC race box? ...I guess finding one for a reasonable price would be pretty few and far between. And a new one would be out of the question.

But hearing that an NA box can last for two years on that much HP makes a TII swap sound a bit easier. I'm tired of having no torque.

 

Same thing back home, St.Croix USVI. Alot of people favor the TII trannies as the stock form handles more power than the NA. Also just wondering..Where did the divide come from I.E.TII vs NA..FC vs FD vs FB. Is it just personal preference or ego? I personally love ROTORIES period, the fb is my choice of ammo(fits my 5'11 frame real well ).

 

The new transmission is installed but I have not driven the car yet. Didn't feel like pulling two cars out of the driveway just to drive the RX-7. We'll see how this one holds up. I'm going to take it easy for the next month but after that it's open season. And my boost controller should arrive tomorrow, so no more wussy 13 PSI.

 

if you crank up the boost that tranny is gonna go KABOOM,Cmon 15 psi plus on a GT40 and bridgeported,good luck buddy.

 

So what is the common weakness in the n/a drivetrain? Just wonder what order I should expect to break things in and maybe see if there is anything I can do to prevent it.

 

damn guy, thats gnarly.

 

How much did you abuse that tranny? Hard launches? Or did you just do alot of WOT pulls? From what I read a long time ago, and it might've been from you, is the NA trannies don't enjoy being put through alot of WOT pulls, launches don't seem to hurt it very much. I could be wrong though.

 

hahaha i have a mint 117k kms tranny here for you if that one breaks lol

what about the miata gears? rebuild kits are cheap, the tranny rebuilding is more intimidating than it is hard

 

I didn't realize how significant this information was when I first read it. Now that I have researched the T-5 a little more, it is pretty clear that the "stock" tailhousing is very short and puts the shifter somewhere in the dash. This isn't going to work for me. Now, I have to believe that if I called my transmission shop and asked for options for relocating T-5 shifters (moving the shifter box backwards) they would have some options. Worst case is that I cut and weld the shift rod and make a custom bracket for the box. But that is starting to sound like a lot of work. Then again, if I can find an early turbo 280Z tailshaft then I'm in business and it almost bolts right in minus the adapter plate (cheap) and the mount (uh, about 30 minutes with the welder and some scrap aluminum).

True enough. The only problem is that if it breaks outside of the city, I better have a plan. On the highway if I loose everything but 4th again it's no big deal, but a hundred miles from home in the middle of Toronto; that could be an issue.

I don't think there's a reason for most people who drive on the street to worry about breaking NA transmissions when doing a TII swap. For stock turbo applications, the transmission would be fine unless the car is being launched.

The common weakness is the transmission according to everyone else. To me, I consider it to be the driveshaft. I've blown up one NA transmission, but two driveshafts. And the driveshafts let go with a a LOT less power.

This transmission has a lot of WOT time on the highway on it. About 50 passes down the 1/4 mile as well. And a few hours on the dyno. Keep in mind that the first three gears are generally just a tire fire which isn't very stressful on the transmission. When the car really digs in in the upper gears is when it starts to feel the hurt. 4th gear would be the safest gear to abuse it in, since the input and output shaft are locked.

The Miata transmission is basically the FC transmission. It's far weaker then the TII unit...

And now, the damage!

Last night I disassembled the transmission to take a look at the destruction. Having not taken a transmission apart before I was surprised that it was quite easy. Just pull the front cover, remove a snap ring holding the input shaft bearing, pull the rear shifter box (there is a split pin you need to drill out), remove the long bolts holding the case together, pull the tailshaft housing and then split everything apart with the aid of a hammer. Very easy.



Hmmm...There seems to be something missing from these gears. I'm not sure the technical name for these gears, so I'll call them the "input gears". Obviously this is the issue with my transmission. As the damage occurred in 3rd, these two gears took the brunt of the torque. This explains why only 4th worked. As these gears transfer power to the cluster shaft for all other gears, if they are totalled, then nothing but 4th is available.



And the missing gear teeth have been found! A few hours of some careful TIG welding and I'm sure she'd be as good as new. Maybe JB-Weld and some SeaFoam? That fixes everything, right?



So knowing what I know now about what's broken, I think I may fix it. I happen to have another NA transmission with a snapped input shaft. It looks like I could just undo two snap rings, then slide the broken gears off of the shaft and slide a good set back on. Any flaw in this plan?

 

Hmmmm.... I foresee already stressed gears being supplemented by newer gears getting jeaolous of their newer counterparts and blowing up to make you upset. But hey, learning is fun!

 

Hummm... You mentioned that you already had a "whine" in 1st thru 3rd on the shredded tranny. If the donor tranny wasn't abused, then I would think that you might want to go a little further into swapping the gear stack. I guess it really depends on how much you trust the donor pieces.

 

Aaron- I figured you had some WOT pulls in it. Also, the person who told me about WOT pulls on N/A transmission's was Adam (mazdaspeed7) but he experienced problems with his setup on a bridgeported motor, but that won't make much of a difference.


How many miles did you get out of it? I know that you are not going WOT and doing hard launches all of the time, just curious what you got out of it?

 

I actually forgot about the whine. After a trip to the 1/4 mile last year, the transmission picked up a whine in the first 3 gears. So maybe it's not really worth putting much effort into. Then again, the transmission that came with the car whined from the moment I bought it until the input shaft let go (ran dry) 100K later.

I'm not sure of the actual mileage. 10K or so? I don't drive as much as I used to. What I tend to think of is in terms of timeframe. Two years of semi-daily driving, plus the 4 months before the big turbo.

 

Honestly, why not consider cryo treating the gears while their out? It's known to make the gears considerably stronger.

And bringing up the Miata parts made me think of something... Why is this 400+hp beast still on a open diff? You should swap in a Torsen rear end if you have some extra time. :P

 

During my NA days, I lost two trannies, on the first one, I lost second gear completly, and on the second one I lost third gear (or fourth, can't remember). I never went to the strip, but I did abused the car

First one had Amsoil gear, and the second one had Red Line...