Kramer
Kramer Dork
12/20/18 12:38 p.m.

I made a $600 offer on a 1994 Miata.  Auto trans.  Stupid or no?  This would be a track rat for me, since i already have a roll bar and other leftovers from my previous Miata.  How expensive/difficult is a trans swap?   How stupid will this car be without a Torsen?  If it is mostly rust free, maybe it would be worth it?  Should I autocross/track it as is until i trash the auto trans?  I'd probably do NASA time  trials and PT, not Spec Miata.  Pic soon

Kramer
Kramer Dork
12/20/18 12:39 p.m.

mazdeuce - Seth
mazdeuce - Seth Mod Squad
12/20/18 12:42 p.m.

Running 1.8 motors are that much around here. 

John Welsh
John Welsh Mod Squad
12/20/18 12:42 p.m.

Even with manual trans and torson this should still be a less than $1,600 car.  Does it seem like it would be a good car at less than $1,600?  

With the auto trans you are assured that the motor has not spent its life up to this point bouncing off the rev limiter.  

Rodan
Rodan HalfDork
12/20/18 1:45 p.m.

I'd be all over that.

5 speed transmissions are pretty cheap... as John said, with a Torsen you'd still be well under $2k.  Nice NA's are $3500 and up.

About this time last year, I bought a nice NB auto, and swapped it to manual.  It's an easy swap mechanically... Transmission, clutch, flywheel, driveshaft, PPF, shifter and clutch pedal assembly.  Everything bolts right in.  On the NA, the speedo cable is mechanical, not sure if that's a direct swap.  I'm not sure what the ECU ramifications are on an NA, on the NB I used a manual ECU, and had to make a few wiring connections.  I get an occasional CEL because the ECU is looking for a clutch switch that isn't there.

 

ManhattanM (fka NY535iManual)
ManhattanM (fka NY535iManual) Reader
12/20/18 3:15 p.m.

You raise a good question.  Your offer is nowhere near stupid, and it depends on what you want the car to be.  Back in October I ran through this analysis to figure out whether converting a local to me cheap auto made sense.  I penciled it out, assuming that I did all the work myself. Here are my thoughts, YMMV.

The guys who wrench on Miata's all the time could have the swap done in half a day, its pretty plug and play deal. If the goal is a low as possible cost track rat, it may be better to buy a whole manual car at the outset.  I say this because to my thinking, getting a cheap auto with the intention of doing a manual swap, creates a bunch of "while you're in there" expenses (fresh gearbox, clutch upgrade, new master cyl/slave,  radiator, ECU, etc.) that would be deferred costs if you bought a manual in the first place, and all those things would add up. I think I figured parts & materials at around 1800 without shopping around and including a new from mazdamotorsports tranny

If you are willing to spend a bit more than bottom dollar, to make it a clean, solid, reliable track car, then an auto conversion can make sense. At a purchase price of $5-800, buying a clean auto car works out pretty well.  If the car has a factory hardtop, any price under $1500-1800 is in the money.  If the idea is to spend under $1500 all-in on a "disposable" car to beat on until it dies, I'd say skip the conversion.

The biggest variable cost is what 5spd to source. It can be surprisingly hard to find a used manual box that is known to be good. (This is why being able to test drive a car thats already a manual is a big plus.) Mazda Motorsports is selling Mazda built units with some of the SM approved upgrades for around $1200.  You can buy used gearboxes all over the place, without quite knowing what you're getting, and rebuilds cost more than what mazdamotorsports sells their new boxes for (which has all the SM transmission builders mighty ticked off.)

I ended up passing on the car since it had rocker rust and smelled like the PO made a habit of pouring buckets of stagnant water onto the carpets, but its still something I'd consider in the future.

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