i think the biggest problem is that every na trans i've gotten already made some kind of noise when i install them the first time. does the na trans not lose as much power as a turbo trans does?

does the supertrapp muffler really quiet the exhaust that much? that would be awesome! i've thought about a supertrapp muffler before. i love the way way they look and are tunable. i just had mixed feelings on how well they flow? it seems like that cap on the en would reduce exhaust flow like crazy. please tell me im wrong . Eric, how much of a power loss do you notice with the supertrapp equipped vs. not using it?

 

I can't tell you how much power the car looses with the Super Trapp end added to the Borla. I am running 12 discs and the spark arrestor cup and it doesn't change the responsiveness or idle speed. The Super Trapp really just breaks up the sound and muffles it a fair bit. I can't tell you about seat of pants or dyno work with it on, as it is only put on the car so I can start it at home and load it on the trailer or to futs around with the car in the driveway. Without the muffler, you can hear the car idling when you are in the house with all the doors and windows closed. With the added Super Trapp, the car can be idling and you can talk in a normal level around the car.

Its not quiet, but I think its liveable and you can reduce the number of discs to quieten the car down even more at the expense of some power.

Regarding the box, the NA trans is just as bad as the TII trans regarding gear ratios. Maybe a bit better. It is also lighter inside which reduces its torque handling capacity and its ability to handle shock loads. The lightness does reduce rotating mass weight of the drivetrain and its also a lighter box, so that helps some. Just treat the box like its glass and it lives okay, LOL.

Eric

 

mine did work, but lasted 2 laps before the stopped making it quieter, and now after 2 track days they are starting to sag... they just aren't built to withstand the sonic booms the rotary provides.

my friend has the quaife gearset in a 340hp miata, and it does fine, actually the stock trans held up ok behind that engine too.

i don't think its realistic to take a 100,000mile used transmission and spin it up to 9,000rpm and expect it to live. minimum should be new bearings and synchros. the miata gearset is an upgrade, too closer gears should be a little easier on the synchro's

 

with the stock port motor that was in the car, i never revved past 7-8k. it has polyurethane motor and tranny mounts and a unsprung 6 puk clutch. the transmissions that i have had, some had bearing noise when cruising steady speeds, other would have bad synchros, some would pop out of gear. all of these were "known good condition" when i bought them from people that "are sure they are good" bs. most of the ones i have gone through didn't even get beat on because of how bad they were when i installed them. i have NEVER rebuilt a transmission before and don't know anyone who has either. to have one rebuilt at a shop is stupid expensive.


anyone know about the supra transmission swap? the transmission that i pulled out of my car made bearing noise when cruising in 5th. i had decided to swap it because i know the powerful new motor would probably destroy it lol.

 

There's no excuse to use an unsprung clutch, ever.

My boss's dad was a drag racer since the 60s, he's forgotten more about racing all sorts of things and breaking things than most of us will ever know, and he told me that they stopped using unsprung disks in the 60s because they were twisting the input shafts of the T10s they were using at the time.

Unsprung disks are harsh on the gears, too. The springs are there for a reason, they give shock loads coming from both ends of the drivetrain a place to get damped out.

The only transmission that I ever broke in the sense of pouring teeth out of the drain hole, was due to using an unsprung clutch.

 

hmm...i hadn't thought of my clutch as being the reason for destruction of so many damn transmissions. when i ordered my clutch i ordered a sprung clutch and i received an unsprung clutch. when i order the new clutch it will be sprung! im going to take that into consideration.

im lost now on which transmission i should use. i cannot afford to pay someone to rebuild my transmission and don't think i have the tools on to rebuild it myself. however i did find a rebuild kit for the na trans for around $300. if anyone knows where i might find a write up for rebuilding it i'll look into that route. that would save me from replacing my brand new na starter with a turbo one along with my brand new slave cylinder.


i remember reading somewhere that the na trans was only good for about 200 bhp new (meaning a mazda replacement). im planing to make more than that to the wheels. i wander if there is a better budget option?

i really appreciate the feedback guys.

 

I put a LOT of shock loading through the transmissions and gets about 5-10k out of a set, at the 180-210hp, 140-160ft-lb torque level. I just grab another used stock unit and keep chugging. I replace them when the bearings start to get noticeably worn, which manifests as either a vibration that happens on the highway in 5th but not 4th, or the shifter moving around as the mainshaft racks back and forth.

Like this:

http://www.youtube.com/watch?v=ockS9tkED9k

Supply of transmissions is drying up, so I'm going to start rebuilding the ones I have. I've found bearing kits online for ~$110 and complete kits with synchros for $180. The problem is the special tools required to disassemble the gear clusters, I don't have them anymore.

 

I have 2 NA boxes and a 3rd with a Miata gearset that I haven't tried yet. I have found that as long as you treat them right and resist 4,000 rpm drops, then they can last for a good long time. The only time I blew an NA trany is when I went to an unsprung clutch as well. Odd, LOL.

If it means anything, I would suggest starting with a good stock NA box, get a rebuild kit for $180, go to a decent local transmission shop and pay them for the 3 hours it takes them to rebuild the tranny. You should be into it for below $500 and that is way lower than you would pay to put in any other kind of box.

Just use good gear lube, I swear by Redline blend of MTL and Shock Load Light. It should handle your power as it has handled mine for over 6 years of race abuse. I do need to repair the 2nd to 3rd synchro it is starting to grind a bit.

Eric

Eric

 

peejay, that is the sound i've heard out of most of my na transmissions lol. it normaly starts after about a week or 2 of driving on them lol.

Eric, you saying take the transmission and rebuild kit to a local shop and pay them for hourly wage to rebuild it? if so, i will make some phone calls tomorrow and see what kind of responses i can get. i guess if i have the kit then half the cost is down. lol. i normally use valvoline syntec blend and don't really even get to abuse the transmissions because they normally make noise before i even get to. i have a rule for if the trans hasn't been driven on in a while i give it another 500 mile "break back in period". and before that time even happens it normally starts making noises

i'll make some phone calls tomorrow and see what happens.

 

If you wanna explore the toyota trans route?.. I would lean more towards the R154, it came out of the MK3 turbo supras. The Getrag 6spd from the MK4 supra is the strongest but very expensive. Dont even think about the W58 transmission from the NA supras!..lol

 

con-3, so the r154 comes from the mk3 turbo supras, thats something i had been trying to piece together. any info on this trans swap? i know a few people make the adapter plate to our 13b. any idea on weight versus our na and turbo trans? i know the supra trans is a lot stronger than our turbo trans, but i wander if it can handle high rpm abuse? i need to recheck on price of the adapter plate and how much the trans sells for. also i need to see if our crossmember will fit it or if i need to make one.

 

the factory sold a close ratio version of the NA trans to put behind the peripheral port race engines in the 80's. it had a slightly beefier case, and synchros, but that's about it. its probably not quite as good as a stock miata trans.

IMO rebuilding an NA trans is pretty cheap in the scheme of things.

 

really? how? my NA trans lasted 100,000 miles before I got to it and then many years after that including serious rallycrosses. Nothing broke on it just the syncros wore out. I was running a 1st gen 13b NA trans too: you just bolt in the 2nd gen tail shaft/shifter assembly on the 1st gen 13b trans and you get shorter1-3 and 5th gear.

I've been Running solid mounts on engine/trans for years now too.

I still haven't broken an axle or a diff yet or a trans for that matter...

I'm calling bullshit on the "weakness" that is the NA drivetrain. I've put it through serious hell.

Sure mathmatically it is weaker you can see the differences between NA and turbo by looking at them, larger ring gear, bigger axle shaft diameter, larger transmission etc but many of us don't need the extra girth.

Granted my motor builds were just a bit over stock, it was driven prettttty hard.

 

Ignore the noise. That's pinion bearings. Watch the shifter change position based on engine load. THAT is mainshaft bearings.

 

i have probably gotten high mileage heavily abused transmissions for the most part.

any how, so i did a search across craigslist and the supra trans is 100% not an option. i didn't find a single one used. it's okay though.

i called a shop near my house that i've sent business to over the years. i know the boss man there, his name is Shawn. were not close or anything but we've been more or less aquatints for about 10 years or so. he said if it's as easy as people say it is, then he'll rebuild the na trans for $300. he's not sure how long it should take because he hasn't rebuilt an rx7 trans in a long time, but he will take his time and make sure it's right. if it's not simple, meaning needing to heat and freeze things to get them apart than the high side would be $500.

even if i swapped a turbo trans i would be looking at about $250 fora trans, $100 for yet another starter (mine is new) and another $50 for a slave cylinder and $140 for a drive shaft. plus it's heavier. im pretty happy about this decision, at least now it's new and should handle my abuse

thanks for the help on that decision guys.

im definitely convinced to go the pp route. more reliable and more output and not really any louder. im going to take racer23's advice and look for a supertrapp and run the borla in the middle. induction will be 65mm efi itb's off an rc51 motorcycle. comes with tps and fuel rail.

should i use msII and build an air box and tune with speed density or use msIII and slap some sock filers on the ram stack and tune with alphaN?

 

More fuel for fire on sprung clutches, where I work even our trucks use sprung clutches, and they are for 2000 lbs/ft



so yeah, sprung is where its at.

 

it is simple, you don't need to heat or freeze anything, i've even done them without the pullers before.

i would take the best shifting one, and it doesn't matter if its loud, the bearings get changed.

 

definitely getting a sprung clutch this time.

the trans that i recently removed from my car is the best i've had (i only had the trans in my car for about a week when i pulled the motor) i only drove on it for a couple hundred miles. jut makes a loud pitch humming noise when cruising between 58-62 mph in 5th gear. other then that, no noise and was the best one for initial take off. the rest of them were kinda rough.

if there's no freezing or heating then it should be $300+$200 for the rebuild kit =$500 fresh transmission im stoked to hear that. eventually i'll probably upgrade to the mazdatrix aluminum drive shaft, but for now i have a mazda reman that has about 5k miles on it

 

I have a buddy who has been using an original Mazda Comp box. Its a 4 speed, but 1st is like a regular box second and 4th is 1:1. He bangs 3 gears to my 2. The other thing it will handle the 9,000 rpm shifts.

The bad, parts are not available any longer as the box is based on an RX3 structure.

Eric

 

too bad parts for them are no longer available and finding one would be hard to come by. were they only used in the rx3 i've seen a few first gens with a 4 speed trans before. i actually almost bought one once lol

 

Competition boxes are usually 1:1 top gear no matter how many gears they have. Minimal drag in top gear that way, since a 1:1 in a RWD box is just directly connecting the input to the output, no load goes through the gears.

Mazda Competition also made a 5-speed box, I don't remember if it's overdrive or not. Quick way to tell is if it has a dogleg 1st or not. (And then there are the weird competition boxes where 1st gear is up and to the right, then 2nd is up and to the left like where 1st is in most transmissions)

If you want fun, the gearbox for the Lancia "037" had a 1st gear something like 2:1 or even 1.9:1, and top (fifth) gear was something like 1.1:1. It was a transaxle so no straight-through top gear. Closest ratios I'd ever seen speced out in an H-gated unit.

Closeness of gears makes higher RPM shifts easier no matter what. 4-5 shift in an SA/FB trans shifts like butter no matter what the RPM is. (But NOT with the huge drop the FC has) 1-2 and 2-3 aren't so nice. Miatas shift great because of their closer gears, even before Mazda went to double-cone synchros on 2nd gear.

 

the SA's had two competition boxes, 1-4 is the same, but they either had a .88 or .82? 5th.

the next closest gear set is the miata.

my friend has the quaife gearset in his miata, and it's pretty outstanding, there is no boost drop between gears, so its a solid 20psi, which in a miata is pretty out there.

 

i broke 3 na trannys in one weekend
swapped for a t2 and good

 

flaco, are you on boost?

do you guys think i should pick up a 1st gen 5 speed trans and have it rebuilt? a friend of mine has a few.

does the miata box swap right in or require machine work on the pilot shaft? i read somewhere that it requires machine work but im not sure.im going to do some searching on the subject.

 

Now when you say "broke3 na trannys" what did you actually break in the transmission? Was it a common failure or root cause?