Alright, so I'm looking at getting a new trans for my 85' since third gear just went out in mine. So i'm wondering what other year trans will fit that would also be 'best' for serious street use. And, are there any 'mods' I could do to one of the same year or later? Besides obvious things like a short throw shifter or polished/lightened gears etc.

Thanks,

-Crispin

 

no experience with the later trannys but anything from 81-85, including gslse, will be a direct bolt in with slight variations in gear ratios. not sure on later models as they use larger diameter flywheels/clutches. the tranny mounts may also be slightly different which may require slight modification to the stock fb mount, making it not quite an exact bolt in swap.

 

It all depends what you want to do. I switched to 81 trans due to lower gearing. The new they got the higher the gearing got. Mazdatrix had a page in the catalog of what gear ratios and transmission gears. Some people use the turbo 2 trans because it is the strongest but it isn't a bolt in.

 

Yeah. I'm not quite sure what I'll go with I'm just searching for ideas.

 

get a earlier 5speed miata tranny and transfer the miata internals into your FB. You just need to shorten the input shaft.

 

Yeah, I've actually got one. And I definetly think it'd be worth while but, I'd rather find some 626 gears. They also interchange. I'm still not sure what I'll do, I need to find out what my local rotary shop has for trannys.
I'm also sorta crammed for time. I planned on painting my car this month.

 

RWD 626 tranny will be hard to find as most of these cars have been recycled but I still see them here in LA every now and then. B2000 trucks are plenty but I have no experience/knowledge.

 

the B2000 has a shorter 1st, so it's a wider gearset than the cars.

 

instead of swapping trannys, because they are aged too and must be worned out as well.
has anyone rebuilt their tranny?
Im thinking of taking that route if its not too expensive

 

It's expensive at all. Unless you need parts like syncros or gears, then you might as well as go find a whole 'working' trans like I prolly will.

 

ive done it. if its just bearings and synchro's its not too bad, but if it needs forks and hubs and stuff it can get expensive.

if its just a "normal" rebuild its probably double the cost of a used trans, but it'll be known good, instead of someone elses old broken one

 

Get a S5 n/a transmission (89-91) and just swap your tailshaft.

 

If everything just bolts in then i'll definetly do it,

 

According to mazdatrix it's more then just the tailshaft.
Bellhousing I think also.

 

nope

 

I quoted this from the mazdatrix website:

'For 1986 thru 1988 (non-turbo) the rear mount location and design was changed. The torque and horsepower of the 13B six-port, coupled with the weight of the 86+ models appears to be approaching the design limit of the transmission. We have heard of some being replaced before 10k miles, and we have replaced/rebuilt more than a few ourselves. Adequate maintenance and lack of abuse appear to definitely be linked to longevity.

With the introduction of the Turbo in 1986, Mazda added a much beefier transmission. This transmission is patterned after the early "Ribcase" 13B 5-speed, and appears to be excellent, but they made it difficult to install in other models. The bellhousing diameter (not the bolt pattern) is larger, the flywheel is larger, the starter is different and mounts further out, and the driveshaft yoke is larger. It can be installed in other cars (we've done a few) but it is not a "Bolt-In".'

 

And although that never actuAally talks about 89-91 trans in particular its still talking about FC trans in general. It never does actually talk about S5 trans.

 

the turbo uses a totally different transmission than the NA FC. the first paragraph is about the NA trans

 

Right.

 

My stock s3 gslse transmission has held up to a few years abuse behind my camden powered 13b

 

I'm not worried about longevity, I just want the gears out 86-88 NT transmissions, because they're much higher. Hoping I can make that swap possible.

 

I have heard the complete 1.6 miata trans will bolt in. No need to swap internal parts.

"Again this is just what I heard".

The two things that may need to be done is how long of drive line and shifter hole.

I will be trying fit it in next month. So I'll know for sure then. But if time's an issuse then I don't know if thats a option for you.

 

the internal parts are fine, except the input shaft gets shortened.

its the EXTERNAL parts, the miata has a different bellhousing bolt pattern, and the rear mount is different.

http://mazdatrix.com/faq/miatainputshaft.htm

 

I have the RWD 626 gearset and it's great. Simply less rpm drop with each shift. 5th gear is short, .858. Throw in a .4625 final drive and you'll never underestimate the speed of a properly geared ported rotary.

I bought a new bearing and synchro kit for $139 shipped off ebay. Cost $600 to have it installed in the trans. Cost another $100 to properly machine the input shaft splines back, and shorten the tip about 1/8". I also supplied the 1st gen case, and Miata tailhousing (built in short throws!). I think that's a good deal.

Use the dual bearing input shaft needle bearing. And with the right spacer you can use the thicker 20.5mm front countershaft bearing from the early 80's Mazda trannies. Otherwise the 15mm one is okay.

I wouldn't attempt to rebuild a trans myself w/o someone who knows what they're doing. Gears chew up fast when installed wrong.

The 1994+ miata trans has dual cones for smoother shifts. That's the one you want if you go Miata route.

 

Mel, if you find one in a boneyard run, send me a text. I want another spare. May be worth a sixer of Heineken's. If you pull it and clean it, a case.