Gearbox is where gears are meshed, pivoted, rotates, synchronizes and spins;
my question is please tell me the theories behind two gearboxes where one is manually shifted up to 6 speed and the other is auto-shifted up to 4 speed but the performance are both the same! During acceleration and momentum and runs the peak maximum speed almost the same rate at any given road condition. Has it something to do with the torque?? Or HP?? But why auto shifted has 4 speed and 6 speed for manual? I gotta know and thanks guys for assistance.

 

Well, if you are tallking about a stock F-body a six speed manual is faster than a four speed automatic. It is harder to launch from a standing start, however. The reason the six speed accelerates harder is that the gearing is lower and that there is less power loss in the transmission.

 

The torque converter (TC) on an automatic helps make up for fewer speeds (gears) than the manual. The TC allows the engine to run at a higher rpm than the transmission input shaft when it is under heavy load, like starting from a stop. This allows the engine to get into it's higher torque range. Also the TC multiplies engine torque at the same time it is slipping. Effectively this acts like and extra gear or two.

Yes, the automatic absorbs some power, but in some applications it can accelerate the car as quickly as a manual. An excellent driver using the manual can beat the driver on an automatic if everything goes well. The automatic vehicle is usually more consistant especially during launch, as Rich said above. In some cases, the automatics are quicker.

Newer automatics are going to 5 and 6 speeds for a number of reasons including acceleration performance, fuel economy and probably emission control as well as marketing reasons where "more gears are better".

 

Yes, what SS said! I was speaking specifically of a stock 4th gen F-body: stock motor, stock rear end, etc. In a given application an auto may be as quick (or quicker) than a manual tranny. The auto also doesn't lose power between shifts like a manual tranny does. Of course, there are the "clutchless" manual trannies like the Lenco, G-Force, etc. The also shift from gear to gear without interrupting the flow of hp but do not use a converter and hence are more efficient. These are used at the highest levels of drag racing.

But the quickest trannies of all are the electronically shifted manual transmissions found in F1 and some other racing series. Now these are appearing on some street cars. Kind of the "best of both worlds" in that they shift very fast but have minimized power loss.

Rich

 

Aha an interesting info .. so the torque converter helps to get an additional power/torque in the A4

thanx OldSStroker and Rich for these great input