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The mkiv Supra Owners Club

BHP through auto boxes.


Matt_J
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I heard a rumour saying there was a limit to the amount of BHP you can put through a supra automatic gearbox. Does anyone know if this is true? If so, what is the amount?

 

Most of the big American boys use auto's. With a upgraded torque converter they have handled around 800BHP if I remember correctly. Maybe more.

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I heard a rumour saying there was a limit to the amount of BHP you can put through a supra automatic gearbox. Does anyone know if this is true? If so, what is the amount?

 

There's a limit to the amount of BHP you can put through ANY gearbox, I think the standard Toyota auto is reputed to be good up to about 500 BHP. With the right rebuild (BoostLogic etc) it will reliably handle more power.

 

IMHO a true 500 BHP is more than enough for a road car, the main problem is transfering it to the tarmac :D

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Driving wise, I like it. It's nice to be able to quickly change down a gear or two without taking your hands off the wheel.

It certainly means you can always be in the right gear at the right time, where if you just leave it in auto, the 'box can get a bit lazy and not change down unless you kick down. Sometimes you don't need full throttle, just a lower gear.

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Is it better than a manual? I heard the 6 speed was described as 'an agricultural gear change'?!

 

It's difficult to say if it's better than a manual. It all depends on what you prefer.

 

I really couldn't say if autos or manuals are better, they're both good. Personally I was only looking for a manual, until I drove an auto, then it was just down to finding the right car.

 

IMHO autos are probably better for normal/town/dragstrip driving and cope OK with track/country lanes. Manuals are better for track/country lanes and cope OK in town/normal/dragstrip driving.

 

After driving an auto for nearly a year, I'm not looking to change it for a manual, but I'm pretty sure I'd feel the same way if it was the other way round, just for different reasons.

 

Either of them make a great car, you won't go far wrong whichever you choose.

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The TT Auto gearbox (A340E) is a very strong auto, but it will break if you are running over 300rwkw. This auto is unique to the 2JZ-GTE engine, despite many other Toyota autos also being labelled as A340E autos. The 300rwkw limit is well below the limit of the Getrag 6 spd gearbox (around 500rwkw), so if you are making serious power, make sure you are using the Getrag box. The W58 5 speed that comes with the non-turbo 2JZ-GE engine can only take around 260rwkw before it will break and the 2JZ-GE auto can only safely handle around 200rwkw.

 

You can make the TT auto box survive longer if you manually change gears when you race it, as this puts most of the torque loading during gear changes through a stronger part of the auto. Also you can get the solonoids upgraded so that it changes gear faster, as this reduces the loading on the auto during gear changes. This will allow for up to 350 rwkw. For it to survive beyond that, you will need very expensive strengthening of internal parts that is offered by several USA Auto transmission companies. When suitably strengthened (at much cost) the auto gearbox can then handle as much power as the Getrag does.

 

 

That was taken from MKIV NZ

 

*Just for reference I belive 350rwkw is approx 500bph

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Dude and Leon both run big power through auto boxes. They both use uprated TC's but not sure about other box internal mods.

 

Having driven both boxes I like both but have a personal preference for the auto. I mainly use the manual side of the box just switching to OD and auto for long distance highspeed hauls, but switch back to manaul when speeds drop. In this weather and low grip levels the auto in much safer in manual mode IMHO.

 

Keep your fluid changes regular and the box will last for a long time.

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