Theoretically, how much torque could the strongest 6-speed manual gearbox take?

[454Casull]

I'm just wondering, since some guy told me that automatics are best for dragging because manuals can't handle the power.

[SaabJohan]

A manual gearbox can generally handle more torque than an automatic gearbox with the same size. The manual also have better effiency.

[454Casull]

So are you saying, that if you enlarge a gearbox (and its internal components) it can handle more torque?

[ivymike1031]

yeah, you can make a gearbox to handle any amount of torque you want. The troubles start when you want to make it small, or spin it quickly.

[454Casull]

or spin it quickly

So the larger it is, the lower the maxium RPMs?

[ivymike1031]

not necessarily, it just gets more and more critical that you properly design the parts if they're big & fast.

[454Casull]

Oh... Thanks.

[BeEfCaKe]

Automatic may actually be better when you really got alota horsepower. This can be seen here (www.exvitermini.com). The drag skyline the owner of the site has put together has been put to a track, using a 6-speed Hollinger manual drag box, but due to the high power output, an automatic gearbox is now being tested for use, just as most other competitors are using.

[Pennzoil GT-R]

theoretically a gearbox can handle any amount of power/torque. i really believe autos are best for acceleration as they can match the revs perfectly on the upshift. this is why alot of race cars now use autos.

[454Casull]

this is why alot of race cars now use autos.

What kind of races?

[Pennzoil GT-R]

F1 use switchable semi-autos for a start, cant get much better than that.

[454Casull]

They're closer to manuals than automatics...

[Polygon]

Originally posted by 454Casull
They're closer to manuals than automatics...

Yeah, they are sequential. There is a still a clutch, it is just controlled by the computer.

[texan]

I feel that automatic transmissions with torque convertors are more ideally suited to high powered applications than traditional manual transmissions. The reason is simple, torque convertors soften the blow engine torque delivers to the gears and clutch packs. What usually breaks in a transmission is the gear teeth, which is either caused by too much torque or too hard a shock load. Manuals naturally shock the gears more by using clutches which grab suddenly, though there are slipper clutches which soften this blow (commonly used in racing bikes). The additional advantage an auto has is in using multiple clutch packs and negating the need for inherently weak synchro mesh gears, which are often the first to fall in a high performance manual tranny.

None of this is to say that either system can't be broken, I only mean that autos naturally soften the hit from a powerful engine, spread the torque out over multiple clutch faces, and do away with brittle synchro gears. Any properly designed transmission should handle the intended torque loads, it's only when you go beyond their design that you find weak points in each system. And remember, it's not horsepower which breaks transmissions, it's torque. A tranny is rated by torque capacity, the horsepower an engine generates has nothing directly to do with whether it will break or not.

[454Casull]

Originally posted by texan
And remember, it's not horsepower which breaks transmissions, it's torque. A tranny is rated by torque capacity, the horsepower an engine generates has nothing directly to do with whether it will break or not.

There has been no mention horsepower in this thread except in yours.