Tougher Gearbox Options

[Cus]

Greetings humans!

I saw this on bookface and though some people hewre might be interested: (BMW GBs into NA/NBs)

https://kmiata.com/blogs/news/big-news-bmw-transmission-upgrade-for-your-miata

[greenMachine]

link to thread on MT.net

I presume you are familiar with the other threads there on gearbox issues.

[The American]

Have been trawling gumtree for zf 6 speed. Are these less common in Aust? Have not seen much to choose from...

[celicapain]

The 6 speeds are rare in aus, the five speeds are plentiful in wreckers though. Im torn. currently making more power than the mx5 5 speed can take, the 6 speed would is marginal and i dont want to keep blowing boxes @ 1500 a pop. Anyone interested in doing a group buy on these kits?

[madjak]

350 - 380whp is plenty for the MX5 chassis which when tuned correctly to limit the torque is fine for stock 6 speeds. I think pushing past that into the realm of 400whp + destroys what the MX5 is good at and makes this conversion a little excessive.

You need to ask yourself what you are trying to make... a super fast car or a undrivable weapon.

[omx500]

I liked my old 5 speed in my NA8. Replaced it with a 6 speed from an SE which had only done very low k's. It always had a lot of drag in neutral, ie when you release the clutch it would pull the idle down and on the flat with the handbrake off would actually pull the car along a bit. It never changed that great either. Perhaps this is an isolated example; damaged or rusted inside or something. Now it often won't let me change into 3rd if I was flat out in second, and moving from 3/4 gate to 5/6 (up or down) is a bit of a lottery. The six speed ZF in the non-M E46 BMW is wonderful to use. If it is strong too without being too heavy or hard to fit then good. While hard to find they are still cheaper than MX5 boxes and being able to use a street style BMW clutch sounds good too. I picked one up from a 75000km 330Ci for $1000 and will wait for the kit to materialize. I've learnt not to hold my breath. I'll post trials and tribulations in case it helps anyone else decide if it is a worthwhile mod.
Omar

[Lokiel]

omx500, Aisin 6-speed boxes are shite, even the new Toyburu-86 has issues with it going from 1st to 2nd when cold.

If I ever needed to do a gearbox change I'd be considering the BMW gearbox rather than installing another Aisin 6-speed.

The miataroadster tall-angled SSK reduced my hatred of the Aising 6-speed gearbox (less miss-shifts and I could actually find reverse reliably).

[Mr Morlock]

I dont get why people think that a baulk or crunch from 1st to 2nd is unusual and that some empathy with things mechanics is unnecessary, Many boy racer cars just abuse gearboxes and unsurprisingly wear the boxes - worn synchros. I was brought up expecting all manual gearboxes crunched 1-2 when cold and my 6 spd confirms it. I am beginning to think an auto is a better choice at least for normal use. Still the subject stands up and for those on track, a stronger box i.e. built for more powerful engines is a valid question. Furthermore modifiers probably enjoy the challenge in re engineering.

[Lokiel]

^
I've got a friend who sold his new 86 within a year of ownership because he often couldn't get 2nd gear when the car was cold and had several near-accidents because of it.
He took it to Toyota three times and all they did was try different gearbox fluids so he sold the car at a significant loss and vowed never to buy a Toyota again.
His case isn't unusual and it seems if your 86 gearbox has this issue, little can be done about it other than replace the gearbox which Toyota dealers wont do under warranty because Toyota doesn't refund them for this.

The fact that the manual Aisin 6-speed gearbox has been around for over 15 years now and is used by multiple Japanese manufacturers and STILL has issues would make me avoid any car with it in future - Mazda chose NOT to use it in the manual ND and developed their own gearbox, that's got to tell you something about their opinion of the manual Aisin 6-speed.

[Mr Morlock]

Sounds an interesting story but I would be absolutely staggered that Mazda make any gearboxes at all. Car makers rely on component suppliers for just about everything except the panels. Mazda along with other car makers set the engineering requirements and then get their selected sources to meet the spec and supply the product. I dont see how Toyota would refuse to replace a gearbox which is substantially flawed. Toyota backs the warranty.

[Daffy]

350 - 380whp is plenty for the MX5 chassis which when tuned correctly to limit the torque is fine for stock 6 speeds. I think pushing past that into the realm of 400whp + destroys what the MX5 is good at and makes this conversion a little excessive.

You need to ask yourself what you are trying to make... a super fast car or a undrivable weapon.

Subscribed!! When I'm running the hi boost (hitting that 380rwhp mark) the problem child is a monster.... I can get more power output winding up boost but she's a street car (and I do want longer engine life). If and when I can start looking at some reasonable track time in the future when I can start committing time for it, or when the SE 6 speed inevitably/eventually does go- thats when I would most like invest in and run with the beemer box. Its great to know the option is out there.

[The American]

I loved shifting the 5speed in my NA8. I really dread the 2-3 shift in my NB...

[Mr Morlock]

further to the "bad " gearboxes i.e. from OEM. Manufacturers in Eu for DSG type transmissions have made some dogs of boxes and it's said that the current Focus is one of them with fixes that apparently don't work. Its arguably common knowledge that these problems have been around with this type of tranny including certain major Euro manufacturers that mislead the public - i.e. cheating on a major corporate scale. I had not heard of problems with 86 but its a heads up check it out. You would have to wonder what constitutes a warranty i.e. if a faulty item is not fixed or replaced then what is the protection for the consumer?

[StillIC]

I dont get why people think that a baulk or crunch from 1st to 2nd is unusual and that some empathy with things mechanics is unnecessary, Many boy racer cars just abuse gearboxes and unsurprisingly wear the boxes - worn synchros. I was brought up expecting all manual gearboxes crunched 1-2 when cold and my 6 spd confirms it. I am beginning to think an auto is a better choice at least for normal use. Still the subject stands up and for those on track, a stronger box i.e. built for more powerful engines is a valid question. Furthermore modifiers probably enjoy the challenge in re engineering.

My NA8 gearbox subscribes to this theory, as did my NA6 gearbox. However, the Aisin 5 speed gearbox I had in my ST162 Celica was the sweetest shifting box I have ever used to this day, and never baulked in any gear, ever. It used Dexron 2 or 3 automatic transmission fluid as specified by Toyota.

[greenltd]

My NBB 6 speed is pretty good noe that my mechanic put "generic" oil in it, probably Burson's. Cold it will shift 1-2-3-4 smoothly, even without the clutch (I'm still practicing 4-5-6 clutchless).
These granted are a slow shift, maybe that is part of the answer.
When warm it's pretty good through all changes.
And my box has been worked hard!

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