miataman86 None
Nov. 10, 2011 5:31 p.m.

I have a '91 Miata and the transmission is gonna be going out in the near future. The 5th-R rod has popped out a few times and I have got it back in place. Most likely, the springs for the rod are broken or something is bent. I plan on replacing the tranny with stock clutch in the near future. Does anyone know of any links, places, and such where i can find a replacement tranny? I've contacted J.O. Motorsports and they have remanufactured Spec Miata trannys for $750 plus shipping. I've got the clutch picked out on 5XRacing.com already. I've searched the web quite a bit so far and the only leads of any real interest I've come across is the J.O. Motorsports. I plan on getting into HPDE by spring and perhaps some autocross by this time next year, so to have a reliable and smooth shifting transmission would be great to have. I prefer to get a rebuilt tranny over just a used one. Thanks for any leads to one.

Nov. 10, 2011 6:51 p.m.

IIRC, Flyin' Miata has close ratio sets and a Quaife $$$ option.

Keith, to the white courtesy phone, please?

Dashpot Reader
Nov. 10, 2011 7:04 p.m.

How many miles on your gearbox? Reasonable service history?

I ask because these gearboxes are very robust and don't break often under stock power. Unless you're putting down big HP a used one should be fine forever.

miataman86 New Reader
Nov. 10, 2011 7:51 p.m.

136,000 miles are on the gearbox. When i changed the fluids in the gearbox and diff, both were dark grey. There has been a "chattering" sort of noise in the tranny since I got her last December and i believe its the 5th-R rod/fork/spring assembly seeing as the 5th-R rod has popped out a few times. The only upgrades to the 1.6 are a Green Filter, Magnecor KV-85 plug cables, and NGK Iridium IX plugs. A few more HP, but I'm not throwing out gobs of power. The service history is probably one of neglegence to the drivetrain. Clutch, flywheel and hydraulic fluid have never been touched and i say that due to the condition of the tranny and diff fluids.

miataman86 New Reader
Nov. 10, 2011 8:11 p.m.

Just checked out FM and I only found trannys in the Salvage Yard. Nothing of any other sort.

codrus New Reader
Nov. 11, 2011 12:50 a.m.

The quaife gearsets that FM offered were quite expensive (IIRC it was a couple grand just for the gearsets, installation not included), and I've heard a couple people say that they weren't enough of an upgrade to justify the cost. Perhaps that's why FM no longer lists them on the web site?

IMHO, if you've got a naturally aspirated Miata, just get a used low-mile 5-speed and throw it in. 30K miles trannies are available -- that should get you another 100K miles easy. If you're pushing a lot of power with a turbo and beating on it on the track, then either accept that 5-speeds are consumables, or find a 6-speed since they're supposed to be stronger.

failboat HalfDork
Nov. 11, 2011 6:43 a.m.

I also wouldnt hesitate for a second to go used.

When I sold my miata it had 176k miles on it, original transmission, working just fine. And the previous owner of my car did a few track days with it too.

miataman86 New Reader
Nov. 11, 2011 2:48 p.m.

Thanks for all of the input on this topic! I really appreciate the feedback. Either 5X Racing or FM for the tranny. If you havent checked out 5X Racing, check em out. Class act race team/online shop. Good guys with GREAT service! I'm running a little more power (5-6 HP) over stock and the engine IS a NA engine. Gonna stick with the 5 speed. Lighter tranny than the 6 and its going to be better overall come the track days. Thanks again!

Kendall_Jones Reader
Nov. 11, 2011 3:00 p.m.

Last time I checked (about a year ago), it was about $1300 for a "crate" trans from Mazda (with all the internal updates) - To have my local guy do a rebuild for a SM it was about the same.

Also, ISC racing in FLA does good miata trans builds.


redstack New Reader
Nov. 11, 2011 5:36 p.m.

Everyone says what bullet proof trans these are but I've noticed several 99's like mine with problems. I mentioned last spring that after a tough track weekend where a buddy and I double teamed the car, that it suddenly wouldn't go into 5th. Let it set all summer while I was at work and when I came home it was OK again. So I'm not totally convinced that a used tran it going to be foolproof, but I'm hopeful. I plan on changing mine because the syncros are just too beat up.

Kendall_Jones Reader
Nov. 11, 2011 5:46 p.m.

Under racing conditions, the miata transmission is like glass. I know guys that can race years on them, and some that shatter syncros in a weekend. Depends how much ham is in your fist.


redstack New Reader
Nov. 11, 2011 5:48 p.m.

Seeing as my buddy isn't here to defend himself, it's all his fault, I'm sure. Honest

Alan Cesar Associate Editor
Nov. 11, 2011 6:09 p.m.

I'd just stick another stock used transmission in there from some Miata salvage outfit. I have 253k mile on my trans, along with quite a bit of autocrossing. Mine's a '91. I was under the impression that at stock power levels, especially with a 1.6, the transmission would likely never break. I could be wrong about that, but it seems to me there are other things likely to break long before the transmission. Differential comes to mind.

Places to go: isellmiataparts.com planet-miata.com and Flyin' Miata's salvage

Those are the places I know of. You can probably get a used trans shipped to your door for less than $300 all in. Don't forget to search your local Craigslist, too. I know in the Chicago area there were always a few people selling parts or parting out a wrecked car at any given time.

Keith SuperDork
Nov. 12, 2011 11:53 a.m.

The sticking reverse is a 1.6 trans thing. Luckily, you can stuff any NA or NB box in. The NB has a few extra synchros and a slightly modified pattern, but a 1.8 NA box is super-easy to find. You've got to be a bit of a hack to break one with a naturally aspirated engine in my opinion.

The Quaife box did not live up to expectations.

redstack New Reader
Nov. 12, 2011 5:14 p.m.

OK I resent that hack part, oh wait I have a Jac's SC Ha off the hook!

miataman86 New Reader
Nov. 13, 2011 3:11 p.m.

I think I'm gonna go with a used tranny for the meanwhile. In the future, I'll definitely upgrade the gearbox to more of a race spec.

miataman86 New Reader
Nov. 18, 2011 5:25 p.m.

Gonna look into getting a 1.8 tranny as opposed to a 1.6 tranny. A little bit beefier and it should fit in place with no problems. Ive talked to a couple of Spec Miata drivers and they said it should mate up perfectly.

Kendall_Jones Reader
Nov. 18, 2011 5:44 p.m.
miataman86 wrote: Gonna look into getting a 1.8 tranny as opposed to a 1.6 tranny. A little bit beefier and it should fit in place with no problems. Ive talked to a couple of Spec Miata drivers and they said it should mate up perfectly.

99+ have all the internal updates. If I was shopping thats what I'd look for (99-04 will fit). There is also a 6 speed, but I'm not a big fan of the ratios.


Keith SuperDork
Nov. 18, 2011 6:29 p.m.

Correct, look for a 1999-05 trans if you want any sort of upgrades. The 1994-97 1.8 are pretty much the same other than a tweak to the reverse forks from what I understand.

If you do go with an NB trans, you'll discover that one of the starter bolts is in the wrong place. You have two options:

  • say "screw it" and just use the two that still line up. A popular option.
  • get the starter and the steel plate that fits between the trans and the block. A bit more money, but you save a chunk of weight with the little NB starter at the same time.

In both cases, get the shifter as well if you can. And no matter what trans you put in, give it good fluid and it shouldn't be a concern.

miataman86 New Reader
Nov. 20, 2011 5:06 p.m.

Yeah, the 1.8 NB tranny is the one I was talking about. I'll prolly go with the second option with the starter in the future. I run Redline synthetics in the tranny, diff, and shifter currently and I love em. Shifts without much effort at all.

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