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Trans for 1.6 NA

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#1
OctaneNation

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"Updating or backdating of transmissions (inclusive of shifters) from 90-05 is permitted; OE shifters must be retained."

 

My car could use a fresh trans. It's currently an early 1.6 version that had the issue with getting stuck in reverse. I have another core from a 1.6 that I took out because of lots of grinding from 4 to 3.

 

Do I build a new box using the best bit from the two that I have, along with new synchros? The bit of research I did said there was no major changes along the way.

 

Buy low mileage new? Rebuild my own? Who sells read-to-go transmissions? I'm in Canada so dealing with a core isn't really feasible.

 

Cheers,

Matt



#2
FTodaro

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I would get an NB transmission and a shifter. the 1.6 box is close to the same but not exactly, i do know that the cost of the parts to rebuild the NA box is more expensive from Mazda, also the NB box and some of its parts like shift rod ends are harder and last longer. IMO you best bet would be to buy a rebuilt NB box. you have to upgrade the shifter as the NA shifter will not work on an NB box.

 

Option two is to rebuild yours if you had someone close by to do it.


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#3
Andy Mitchell

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Nah, the NA shifter will work on the NB box - you just need to knock one of the locator pins out of the turret.

 

Rebuilding a trans is not rocket science (despite the impression you might get from reading posts on the internet). Just do it, like the Nike ads say,

 

OctaneNation, you're in Canada? And we don't know each other? Such a small place. We should do PM's sometime.  :) 


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#4
SaulSpeedwell

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My opinion:  If it was my own car, I'd rather rebuild a good NA core than a bad NB core - particularly if you do NOT run tracks with a difficult 3-2 downshift (in which case a dual-cone 2nd 94-05 box may be better for you).   If you continued to drive it for multiple sessions after it started grinding, you've added maybe $100+ of non-sacrificial non-brass parts (i.e. the sliders) to the build cost.  A street core may make more sense at that point.  Or use what you have as your learning experience.

 

It is true it is not rocket science to rebuild the trans. But if you add up making the special tools, the research, and learning to do it?  You will probably have 16 hours in the first rebuild?  If you fabricate fast or borrow existing tools to copy and already have presses and pullers, maybe you'll have it done in 8 hours.  But now you are set forever.  After the 3rd or 4th one, you will have broken even.  If you do them for others, now you are making money.  And then your life is ruined :)

 

I always tell people if you are going to do 4+, sure, learn to do it yourself.  Or if you are in this for DIY project fun instead of for wins and laptimes,  If you get good life out of trans and are short on time?  Better to farm it out, IMO. 


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#5
OctaneNation

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Like this missed 3-2 while leading the race? https://youtu.be/NG01IKecK6Y?t=16m



#6
Bench Racer

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Matt, contrary to the belief of some on this site, I've got an almost free deal for you, other than whatever for across the border, ship box and shipping costs. The original transmission from my car was taken out (shifted ok for street use) during build and a 99 plus transmission with 23,000 miles was put in. For a learning process I had tools made and took the original transmission apart last fall. It's 100 percent in loose pieces, could put all or whatever parts you need in box and ship. A couple of snap-rings are junk. I'd give instructions to make the loooog deep well socket and if you weld, for approx. $30.00 you could make your own. IIRC $10.00 for the socket and then cut in half, one end for socket/nut, other end for socket handle/torque wrench and weld them to a piece of $20.00 tubing. Would need to check socket size and tubing diameter and length. For taking the transmission apart I managed with my existing 3 jaw puller I modified and another normal puller I have.

 

Let me know if your interested and if you need all or just parts.

 

I've got a Pro rebuilt backup transmission.


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#7
SaulSpeedwell

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Like this missed 3-2 while leading the race? https://youtu.be/NG01IKecK6Y?t=16m

 

LOL.  Not exactly.  The gate precision has nothing to with whether you have a single cone or dual cone 2nd.  It is all about the motor mounts, shift selectors, and hand position.  Look how much your shifter is moving at 15:18, 15:40, etc.  Get those motor mounts stiffened up, pre-stressed toward the outside, etc. :)

 

At risk of offending you .... you are  "pistol gripping" quite a bit.  Keeping your hand on top (as if dropping an egg vertically) will help you find the gates despite that the PPF is moving around. Slick shift balls help, too, because your palm friction is 100X less than pictol gripping while your body is sloshing in the same direction as the PPF is sloshing - but when you clutch, the PPF rebounds back the opposite direction of the motor torque.   With a perfectly precise trans, you may not need to alter anything.  But nothing to do with the 1 cone vs 2 cone 2nd synchro, that's all I'm saying.


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#8
OctaneNation

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I have a couple seasons on the comp motor mounts but I'll have to double check them and the diff mounts...



#9
BNaumann

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#10
davew

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I rebuild a LOT of these transmissions. Over 50 this year alone, and it is only March. My record is 54 minutes, start to finish. Typically with cleaning time it takes me 3 hours to rebuild. I have a dedicated bench, with dedicated tools. The hot tank is next to my bench and the press is next to the hot tank. I stock every part needed to rebuild any year trans and have 100's of spare/used parts. I don't take more than 4 steps to get to any trans tool, equipment or parts.

 

Typical new parts cost from Mazda is $500. This varies slightly depending upon year and condition of the donor trans.

 

Special service tools: long socket, long bearing puller, big socket for main shaft nut will cost $100 to make and several hours.

 

Is it worth your time and effort to build it yourself? Only you can decide. Is there great satisfaction in doing it yourself rather than paying someone else, sure.

 

Dave


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#11
Andy Mitchell

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Is it worth your time and effort to build it yourself? Only you can decide. Is there great satisfaction in doing it yourself rather than paying someone else, sure.

 

Dave

 

Certainly agree with all of this (and what Mr. Speedwell said earlier).

 

But if you live way out in the boonies (like I do), shipping costs (both ways, new one to you, core back to your rebuilder) can start to add up. Plus, I am the kind of idiot that takes stuff apart just to see how it works. So rather than swap in a junker last time around I gave rebuilding a shot myself. And it wasn't actually all that difficult to do. I found a great guide on one of the other Mazda forums (complete with lots of photos) to help, and even though I don't think it was necessary, having that helped a lot with my confidence. Anyway, it all worked when I finished, and now I know what the guts of a transmission look like - so I count that as a double win in my books!

 

Would I do it again? Depends on how rich I was feeling at the time, I guess. I hate the stink of trans lube, and it goes everywhere. And there wouldn't be any thrill of accomplishment next time around, it would seem like pure drudge work. But hey, so do brakes - and I do those over and over.

 

Yer pays yer money and yer takes yer choice, I guess. :-)


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#12
BNaumann

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pre-stressed toward the outside


Can you elaborate on this? Are you just prying the subframe side outward, or spacing the engine side outward?

#13
SaulSpeedwell

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Can you elaborate on this? Are you just prying the subframe side outward, or spacing the engine side outward?

 

I ran two tracks where difficult 2-3 shifts could lose you a race.  Both 2-3 shifts were RH corners, and the tendency was to hit 5th or "mystery gear" (I think Ken Zalner invented this term, where you just bonk off of some dead space between 1-3 or 3-5).  So I would "jack" the PPF/motor for max compression to the left motormount when I torqued it all down.  I believe it helped with the windup/recoil that happens from the lateral acceleration versus the "unwinding" when clutching.

 

I admit this could be a bit anecdotal, but it seemed to help.  The cars that missed a lot of 2-3 shifts would shake the motor a lot on startup, or be physically able to be "shaken" if you just grabbed the oil cap on the valve cover.  A lot of oil-soaked/torn motor mounts out there, IMO.   


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#14
davew

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Saul is correct, use new or very good motor mounts. The Mazda comp mounts are the same price and fit just like your worn out stock units.

 

The 2-3 shift is tricky. As you prepare for the shift, your hand knows where 2nd gear is and anticipates where 3rd gear is. When you release the gas to shift, the entire drive train moves in the mounts. Which relocates 3rd gear to someplace your hand does not compensate for.

 

To cure this, let go of the shifter. Bump it into Neutral, then release the shifter. There are 2 small spring that will line everything up perfectly for a bump back up to 3rd gear. The bump/release/bump only takes 1/2 a second, but makes the 2-3 shift a reliable shift.

 

Other hints, use a stock shifter (required for SM) rather than a short shift kit. And, use the stock shift ball. The internal springs (mentioned above) are matched to the weight of the shift ball and the length of the lever.

 

Stock shifter + stock shift ball + bump/release/bump will make 2-3 shifts easy. (new springs help too)

 

Dave


Dave Wheeler
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#15
Alberto

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Would stiffer diff bushings (poly) help this?


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#16
davew

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No, motor still moves


Dave Wheeler
Advanced Autosports, the nations most complete Spec Miata shop
Author, Spec Miata Constructors Guide, version 1 and 2.0

Building Championship winning cars since 1995

3 time consecutive Central DIvision Champion car builder 2012-2013-2014

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2007 June Srints winner, (GT1, Mohrhauser)

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#17
BNaumann

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Thanks for the tips guys.  I do have new Mazdaspeed motor mounts in the car, which made a big difference, but as "Saul" alluded to I've also noticed that lateral loads move the motor more than the gobs of torque that it produces.  I have similar 2-3 shift problems especially with a particular right hand hill crest.  I know patience is a virtue but we're all trying to shift like Hille...



#18
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I know patience is a virtue but we're all trying to shift like Hille...

To be like Hille, coolness is required with his patience.


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