一個(gè)短期課程自動(dòng)變速器由查爾斯奧法里現(xiàn)代自動(dòng)變速器是迄今為止，在今天的汽車最復(fù)雜的機(jī)械部件。自動(dòng)變速器包括機(jī)械系統(tǒng)，液壓系統(tǒng)，電氣系統(tǒng)和計(jì)算機(jī)控制的所有完美的結(jié)合在一起，幾乎沒有什么問題。本文將幫助您了解里面的這些技術(shù)奇跡和修復(fù)他們當(dāng)他們失敗的時(shí)候去什么概念。本文分為以下五個(gè)部分：?什么是傳輸打破了最簡單的傳輸?shù)哪康氖鞘裁础?傳動(dòng)部件描述了每個(gè)系統(tǒng)的一般原理簡單來說幫助您了解如何自動(dòng)變速器廠。?發(fā)現(xiàn)問題變得更糟之前他們表示要尋求防止小問題變成大。?維護(hù)談?lì)A(yù)防性維護(hù)，每個(gè)人都應(yīng)該知道的。?傳輸修理了修理通常從輕微的調(diào)整傳輸完成檢修類型。________________________________________傳輸是什么？變速器是連接到后面的引擎，將發(fā)動(dòng)機(jī)動(dòng)力傳遞到驅(qū)動(dòng)輪的裝置。汽車發(fā)動(dòng)機(jī)處于最佳狀態(tài)，在一定的轉(zhuǎn)速運(yùn)行（轉(zhuǎn)每分鐘）的范圍和它傳輸?shù)墓ぷ饕源_保動(dòng)力傳遞給驅(qū)動(dòng)輪的同時(shí)保持該范圍內(nèi)的發(fā)動(dòng)機(jī)。它是通過不同的齒輪組合。在第一輪，發(fā)動(dòng)機(jī)將關(guān)系到驅(qū)動(dòng)輪的速度更快，而在高速運(yùn)轉(zhuǎn)的發(fā)動(dòng)機(jī)，即使是蛇王的汽車可能會(huì)超過 70 英里的。除了不同的前進(jìn)檔，變速器也有一個(gè)中立的立場(chǎng)斷開發(fā)動(dòng)機(jī)與驅(qū)動(dòng)輪，反向，使驅(qū)動(dòng)輪向相反的方向轉(zhuǎn)讓你回來了。最后，有停車位。在這個(gè)位置，閂鎖機(jī)制（不像門上的鎖舌鎖定）插入輸出軸的槽，鎖驅(qū)動(dòng)輪和阻止轉(zhuǎn)動(dòng)，從而防止汽車移動(dòng)。有兩種基本類型的自動(dòng)變速器的車輛是否是后輪驅(qū)動(dòng)、前輪驅(qū)動(dòng)。在后輪驅(qū)動(dòng)的汽車，變速器通常安裝在發(fā)動(dòng)機(jī)后端和位于下底盤中心與油門踏板位置。驅(qū)動(dòng)軸連接傳輸后，位于后橋最終的驅(qū)動(dòng)和用于將動(dòng)力傳遞給后輪。功率流系統(tǒng)是簡單直接地從發(fā)動(dòng)機(jī)，通過液力變矩器，然后通過變速器、傳動(dòng)軸，直到最后傳動(dòng)是分送到兩個(gè)后車輪。傳輸是什么？變速器是連接到后面的引擎，將發(fā)動(dòng)機(jī)動(dòng)力傳遞到驅(qū)動(dòng)輪的裝置。汽車發(fā)動(dòng)機(jī)處于最佳狀態(tài)，在一定的轉(zhuǎn)速運(yùn)行（轉(zhuǎn)每分鐘）的范圍和它傳輸?shù)墓ぷ饕源_保動(dòng)力傳遞給驅(qū)動(dòng)輪的同時(shí)保持該范圍內(nèi)的發(fā)動(dòng)機(jī)。它是通過不同的齒輪組合。在第一輪，發(fā)動(dòng)機(jī)將關(guān)系到驅(qū)動(dòng)輪的速度更快，而在高速運(yùn)轉(zhuǎn)的發(fā)動(dòng)機(jī)，即使是蛇王的汽車可能會(huì)超過 70 英里的。除了不同的前進(jìn)檔，變速器也有一個(gè)中立的立場(chǎng)斷開發(fā)動(dòng)機(jī)與驅(qū)動(dòng)輪，反向，使驅(qū)動(dòng)輪向相反的方向轉(zhuǎn)讓你回來了。最后，有停車位。在這個(gè)位置，閂鎖機(jī)制（不像門上的鎖舌鎖定）插入輸出軸的槽，鎖驅(qū)動(dòng)輪和阻止轉(zhuǎn)動(dòng)，從而防止汽車移動(dòng)。有兩種基本類型的自動(dòng)變速器的車輛是否是后輪驅(qū)動(dòng)、前輪驅(qū)動(dòng)。在后輪驅(qū)動(dòng)的汽車，變速器通常安裝在發(fā)動(dòng)機(jī)后端和位于下底盤中心與油門踏板位置。驅(qū)動(dòng)軸連接傳輸后，位于后橋最終的驅(qū)動(dòng)和用于將動(dòng)力傳遞給后輪。功率流系統(tǒng)是簡單直接地從發(fā)動(dòng)機(jī)，通過液力變矩器，然后通過變速器、傳動(dòng)軸，直到最后傳動(dòng)是分送到兩個(gè)后車輪。在一個(gè)前輪驅(qū)動(dòng)的汽車，變速器通常是結(jié)合形成所謂的最終驅(qū)動(dòng)橋。在一個(gè)前輪驅(qū)動(dòng)的汽車發(fā)動(dòng)機(jī)通常是安裝在車側(cè)與跨橋塞在它所面臨的汽車后部的發(fā)動(dòng)機(jī)側(cè)。前車軸是直接連接到驅(qū)動(dòng)橋和提供電力的前輪。在這個(gè)例子中，功率流從發(fā)動(dòng)機(jī)，通過液力變矩器到一個(gè)大型鏈條將動(dòng)力通過一個(gè) 180 度的轉(zhuǎn)向傳動(dòng)是沿側(cè)發(fā)動(dòng)機(jī)。從那里，權(quán)力是經(jīng)由傳輸?shù)阶詈蟮尿?qū)動(dòng)器，這是分裂，通過傳動(dòng)軸傳遞給兩個(gè)前輪。有一些其他的安排，包括前輪驅(qū)動(dòng)車輛的發(fā)動(dòng)機(jī)安裝前后而不是橫著有其它系統(tǒng)，四輪驅(qū)動(dòng)，但兩種系統(tǒng)是目前最受歡迎的。一個(gè)不太常見的后驅(qū)布置變速器直接安裝到最后的驅(qū)動(dòng)器后部和由傳動(dòng)軸扭矩轉(zhuǎn)換器，仍然是安裝在發(fā)動(dòng)機(jī)的連接。本系統(tǒng)是在新出廠的發(fā)現(xiàn)，用以平衡的重量均勻地在前輪和后輪之間的改進(jìn)的性能和處理。另一個(gè)后輪驅(qū)動(dòng)系統(tǒng)安裝一切，發(fā)動(dòng)機(jī)，傳輸和最終的驅(qū)動(dòng)器，在后面。這發(fā)動(dòng)機(jī)后置的布置上流行的保時(shí)捷。________________________________________傳動(dòng)部件現(xiàn)代自動(dòng)變速器是由設(shè)計(jì)，在一個(gè)巧妙的機(jī)械交響樂團(tuán)一起工作的許多部件和系統(tǒng)，液壓和電氣技術(shù)，經(jīng)過多年的發(fā)展，在許多機(jī)械傾向的人認(rèn)為是一種藝術(shù)形式。我們嘗試使用簡單的，通用的解釋來描述這些系統(tǒng)，但是，由于一些復(fù)雜的組件，您可能需要使用一些可視化的操作。組成自動(dòng)變速器的主要部件包括：?行星齒輪組，提供不同的前進(jìn)檔和倒檔的機(jī)械系統(tǒng)。?液壓系統(tǒng)采用一種特殊的傳動(dòng)液被泵的壓力下通過閥體控制離合器和為帶控制行星齒輪組。?密封件和墊片使用機(jī)油那里應(yīng)該是和防止漏油。?液力變矩器就像一個(gè)離合器允許車輛來齒輪停止而發(fā)動(dòng)機(jī)仍在運(yùn)行。?調(diào)節(jié)器、節(jié)流閥電纜監(jiān)測(cè)速度和為節(jié)氣門位置確定時(shí)移。?新型車輛，換擋點(diǎn)由計(jì)算機(jī)引導(dǎo)電螺線管改變油流到適當(dāng)?shù)慕M件在正確的即時(shí)控制。行星齒輪組在一個(gè)前輪驅(qū)動(dòng)的汽車，變速器通常是結(jié)合形成所謂的最終驅(qū)動(dòng)橋。在一個(gè)前輪驅(qū)動(dòng)的汽車發(fā)動(dòng)機(jī)通常是安裝在車側(cè)與跨橋塞在它所面臨的汽車后部的發(fā)動(dòng)機(jī)側(cè)。前車軸是直接連接到驅(qū)動(dòng)橋和提供電力的前輪。在這個(gè)例子中，功率流從發(fā)動(dòng)機(jī)，通過液力變矩器到一個(gè)大型鏈條將動(dòng)力通過一個(gè) 180 度的轉(zhuǎn)向傳動(dòng)是沿側(cè)發(fā)動(dòng)機(jī)。從那里，權(quán)力是經(jīng)由傳輸?shù)阶詈蟮尿?qū)動(dòng)器，這是分裂，通過傳動(dòng)軸傳遞給兩個(gè)前輪。有一些其他的安排，包括前輪驅(qū)動(dòng)車輛的發(fā)動(dòng)機(jī)安裝前后而不是橫著有其它系統(tǒng)，四輪驅(qū)動(dòng)，但兩種系統(tǒng)是目前最受歡迎的。一個(gè)不太常見的后驅(qū)布置變速器直接安裝到最后的驅(qū)動(dòng)器后部和由傳動(dòng)軸扭矩轉(zhuǎn)換器，仍然是安裝在發(fā)動(dòng)機(jī)的連接。本系統(tǒng)是在新出廠的發(fā)現(xiàn)，用以平衡的重量均勻地在前輪和后輪之間的改進(jìn)的性能和處理。另一個(gè)后輪驅(qū)動(dòng)系統(tǒng)安裝一切，發(fā)動(dòng)機(jī)，傳輸和最終的驅(qū)動(dòng)器，在后面。這發(fā)動(dòng)機(jī)后置的布置上流行的保時(shí)捷。________________________________________傳動(dòng)部件現(xiàn)代自動(dòng)變速器是由設(shè)計(jì)，在一個(gè)巧妙的機(jī)械交響樂團(tuán)一起工作的許多部件和系統(tǒng)，液壓和電氣技術(shù)，經(jīng)過多年的發(fā)展，在許多機(jī)械傾向的人認(rèn)為是一種藝術(shù)形式。我們嘗試使用簡單的，通用的解釋來描述這些系統(tǒng)，但是，由于一些復(fù)雜的組件，您可能需要使用一些可視化的操作。組成自動(dòng)變速器的主要部件包括：?行星齒輪組，提供不同的前進(jìn)檔和倒檔的機(jī)械系統(tǒng)。?液壓系統(tǒng)采用一種特殊的傳動(dòng)液被泵的壓力下通過閥體控制離合器和為帶控制行星齒輪組。?密封件和墊片使用機(jī)油那里應(yīng)該是和防止漏油。?液力變矩器就像一個(gè)離合器允許車輛來齒輪停止而發(fā)動(dòng)機(jī)仍在運(yùn)行。?調(diào)節(jié)器、節(jié)流閥電纜監(jiān)測(cè)速度和為節(jié)氣門位置確定時(shí)移。?新型車輛，換擋點(diǎn)由計(jì)算機(jī)引導(dǎo)電螺線管改變油流到適當(dāng)?shù)慕M件在正確的即時(shí)控制。行星齒輪組自動(dòng)變速器包括許多不同的齒輪組合。在一個(gè)手動(dòng)變速箱齒輪沿軸向滑動(dòng)，當(dāng)你移動(dòng)換擋桿從一個(gè)位置到另一個(gè)，從事各種大小齒輪的要求，提供正確的傳動(dòng)比。然而在自動(dòng)變速器中，齒輪，不移動(dòng)，并保持嚙合。這是通過行星齒輪組完成?；镜男行驱X輪裝置由一個(gè)太陽輪，齒圈和兩個(gè)或兩個(gè)以上的行星齒輪，所有剩余的常嚙合。行星齒輪連接到彼此通過一個(gè)共同的載體，使齒輪旋轉(zhuǎn)軸稱為“小齒輪” ，這是附著在載體。一種方式，該系統(tǒng)可應(yīng)用的一個(gè)例子是連接到齒圈發(fā)動(dòng)機(jī)的輸入軸連接，行星架與輸出軸，并鎖定太陽齒輪，使它不能動(dòng)。在這種情況下，當(dāng)我們轉(zhuǎn)動(dòng)齒圈，行星將“走” 著太陽輪（這是固定）導(dǎo)致行星架轉(zhuǎn)動(dòng)輸出軸在同一方向的輸入軸，但速度較慢的速度，導(dǎo)致齒輪減速（類似汽車的第一齒輪）。如果我們解開太陽齒輪和鎖的任何兩個(gè)元素，這將導(dǎo)致所有三個(gè)要素，把在相同的速度，從而使輸出軸將速度作為輸入軸同轉(zhuǎn)率。這就像一輛汽車是第三或高齒輪。另一種方式，我們可以使用一個(gè)行星齒輪組是由行星架固定移動(dòng)，然后運(yùn)用權(quán)力環(huán)帶動(dòng)太陽輪反向給我們倒檔齒輪。右邊的圖顯示上述簡單的系統(tǒng)將在一個(gè)實(shí)際的傳輸。輸入軸連接到環(huán)形齒輪（藍(lán)色），輸出軸與行星架（綠色）和單向離合器單向離合器（也被稱為“斜撐離合器）是一種裝置，將允許一個(gè)組件如環(huán)形齒輪轉(zhuǎn)一個(gè)方向而不是在其他。這種效果是一樣的自行車，在踏板將車輪向前蹬踏，但將自旋自由時(shí)，后蹬。一個(gè)單向離合器是用來在第一齒輪時(shí)，移相器在驅(qū)動(dòng)位置。當(dāng)你開始加速從停止，開始在第一齒輪傳動(dòng)。你有沒有注意到，如果你釋放的氣體，而它仍然是在第一輪會(huì)發(fā)生什么？汽車?yán)^續(xù)滑行仿佛你是在中性?，F(xiàn)在，切換到低速齒輪代替開車。當(dāng)你停止加油，在這種情況下，你會(huì)感覺到發(fā)動(dòng)機(jī)放慢你像一個(gè)標(biāo)準(zhǔn)的移動(dòng)車。這是因?yàn)樵隍?qū)動(dòng)，一個(gè)單向離合器使用而在低，離合器或者是用帶。樂隊(duì)一種帶是一種摩擦材料的內(nèi)表面的鋼表帶。該帶的一端固定在變速器殼體上，另一端連接到伺服。在適當(dāng)?shù)臅r(shí)間，液壓油被送到伺服壓力收緊帶在滾筒停止?jié)L筒轉(zhuǎn)動(dòng)下。液力變矩器在自動(dòng)變速器，液力變矩器以標(biāo)準(zhǔn)換檔車輛離合器的地方。它的存在是為了讓發(fā)動(dòng)機(jī)繼續(xù)運(yùn)行，當(dāng)車輛停止時(shí)。液力變矩器的原理就像一扇是插入吹向另一個(gè)的風(fēng)扇。如果你抓住拔掉風(fēng)扇葉片，你可以把它舉行，但只要你放手，它就會(huì)開始加速，直到它接近風(fēng)扇轉(zhuǎn)速的動(dòng)力。與液力變矩器不同的是，而不是使用空氣，它使用油或傳動(dòng)液，更精確。液力變矩器是一種形裝置的大炸圈餅（10“至 15”的直徑），安裝在發(fā)動(dòng)機(jī)與變速器之間的。它由三個(gè)內(nèi)部元素一起發(fā)射功率的傳輸。變矩器的三個(gè)要素是泵，渦輪，和定子。泵直接安裝的轉(zhuǎn)換器殼體依次是直接連接到發(fā)動(dòng)機(jī)的曲軸和發(fā)動(dòng)機(jī)轉(zhuǎn)速轉(zhuǎn)。渦輪機(jī)內(nèi)的房屋和直接連接到傳輸提供動(dòng)力以驅(qū)動(dòng)車輛的輸入軸。定子安裝在單向離合器使它可以自由旋轉(zhuǎn)在一個(gè)方向而不是其他的。三種元素各有鰭安裝在他們正是直接通過變矩器的油流在發(fā)動(dòng)機(jī)運(yùn)轉(zhuǎn)時(shí)，傳動(dòng)液進(jìn)入泵部分，是由離心力向外推，直至使其轉(zhuǎn)動(dòng)的渦輪。流體不斷循環(huán)運(yùn)動(dòng)回到定子渦輪中心。如果渦輪速度低于泵，液體會(huì)與定子的定子翅片，推到單向離合器的前接觸并阻止它旋轉(zhuǎn)。停止與定子，液體由葉輪重新泵在“幫助” 的角度提供扭矩增加。由于渦輪速度趕上泵，流體開始攻擊靜子葉片造成定子在同一方向轉(zhuǎn)動(dòng)泵和渦輪背面。隨著速度的增加，這三個(gè)要素開始轉(zhuǎn)向在大約相同的速度。年代以來，為了提高燃油經(jīng)濟(jì)性，變矩器配備了鎖止離合器（未顯示），鎖定為渦輪泵的車輛速度達(dá)到約 45 - 50 英里。這是鎖定計(jì)算機(jī)控制，通常不會(huì)進(jìn)行，除非是在第三或第四齒輪傳動(dòng)。液壓系統(tǒng)液壓系統(tǒng)是一個(gè)復(fù)雜的通道和管發(fā)送傳輸流體壓力的傳動(dòng)與液力變矩器的所有部件在迷宮。在左邊的圖是從 3 速自動(dòng)從 60 年代的一個(gè)簡單的。新系統(tǒng)更復(fù)雜，結(jié)合計(jì)算機(jī)電氣元件。傳動(dòng)液用于多項(xiàng)用途，包括：變速控制，一般潤滑和冷卻變速器。不像發(fā)動(dòng)機(jī)，主要采用油潤滑，一個(gè)傳輸功能的各個(gè)方面的壓力下，依賴于不斷提供的液體。這是不同于人類的循環(huán)系統(tǒng)（液體甚至是紅色）甚至幾分鐘的操作時(shí)，有一個(gè)缺乏的壓力可能是有害的或傳輸?shù)纳钌踔潦侵旅?。為了保持變速器在正常工作溫度，流體的一部分是通過一到兩個(gè)鋼管專用室 THA 派A Short Course onAutomatic Transmissionsby Charles OfriaThe modern automatic transmission is by far, the most complicated mechanical component in today's automobile. Automatic transmissions contain mechanical systems, hydraulic systems, electrical systems and computer controls, all working together in perfect harmony which goes virtually unnoticed until there is a problem. This article will help you understand the concepts behind what goes on inside these technological marvels and what goes into repairing them when they fail.This article is broken down into five sections:? What is a transmission breaks down in the simplest terms what the purpose of a transmission is. ? Transmission Components describes the general principals behind each system in simple terms to help you understand how an automatic transmission works. ? Spotting problems before they get worse shows what to look for to prevent a minor problem from becoming major. ? Maintenance talks about preventative maintenance that everyone should know about. ? Transmission repairs describes the types of repairs that are typically performed on transmissions from minor adjustments to complete overhauls. What is a transmission?The transmission is a device that is connected to the back of the engine and sends the power from the engine to the drive wheels. An automobile engine runs at its best at a certain RPM (Revolutions Per Minute) range and it is the transmission's job to make sure that the power is delivered to the wheels while keeping the engine within that range. It does this through various gear combinations. In first gear, the engine turns much faster in relation to the drive wheels, while in high gear the engine is loafing even though the car may be going in excess of 70 MPH. In addition to the various forward gears, a transmission also has a neutral position which disconnects the engine from the drive wheels, and reverse, which causes the drive wheels to turn in the opposite direction allowing you to back up. Finally, there is the Park position. In this position, a latch mechanism (not unlike a deadbolt lock on a door) is inserted into a slot in the output shaft to lock the drive wheels and keep them from turning, thereby preventing the vehicle from rolling. There are two basic types of automatic transmissions based on whether the vehicle is rear wheel drive or front wheel drive. On a rear wheel drive car, the transmission is usually mounted to the back of the engine and is located under the hump in the center of the floorboard alongside the gas pedal position. A drive shaft connects the rear of the transmission to the final drive which is located in the rear axle and is used to send power to the rear wheels. Power flow on this system is simple and straight forward going from the engine, through the torque converter, then through the transmission and drive shaft until it reaches the final drive where it is split and sent to the two rear wheels.On a front wheel drive car, the transmission is usually combined with the final drive to form what is called a transaxle. The engine on a front wheel drive car is usually mounted sideways in the car with the transaxle tucked under it on the side of the engine facing the rear of the car. Front axles are connected directly to the transaxle and provide power to the front wheels. In this example, power flows from the engine, through the torque converter to a large chain that sends the power through a 180 degree turn to the transmission that is along side the engine. From there, the power is routed through the transmission to the final drive where it is split and sent to the two front wheels through the drive axles. There are a number of other arrangements including front drive vehicles where the engine is mounted front to back instead of sideways and there are other systems that drive all four wheels but the two systems described here are by far the most popular. A much less popular rear drive arrangement has the transmission mounted directly to the final drive at the rear and is connected by a drive shaft to the torque converter which is still mounted on the engine. This system is found on the new Corvette and is used in order to balance the weight evenly between the front and rear wheels for improved performance and handling. Another rear drive system mounts everything, the engine, transmission and final drive in the rear. This rear engine arrangement is popular on the Porsche.Transmission Components The modern automatic transmission consists of many components and systems that are designed to work together in a symphony of clever mechanical, hydraulic and electrical technology that has evolved over the years into what many mechanically inclined individuals consider to be an art form. We try to use simple, generic explanations where possible to describe these systems but, due to the complexity of some of these components, you may have to use some mental gymnastics to visualize their operation.The main components that make up an automatic transmission include:? Planetary Gear Sets which are the mechanical systems that provides the various forward gear ratios as well as reverse. ? The Hydraulic System which uses a special transmission fluid sent under pressure by an Oil Pump through the Valve Body to control the Clutches and the Bands in order to control the planetary gear sets. ? Seals and Gaskets are used to keep the oil where it is supposed to be and prevent it from leaking out. ? The Torque Converter which acts like a clutch to allow the vehicle to come to a stop in gear while the engine is still running. ? The Governor and the Modulator or Throttle Cable that monitor speed and throttle position in order to determine when to shift. ? On newer vehicles, shift points are controlled by Computer which directs electrical solenoids to shift oil flow to the appropriate component at the right instant. Planetary Gear SetsAutomatic transmissions contain many gears in various combinations. In a manual transmission, gears slide along shafts as you move the shift lever from one position to another, engaging various sized gears as required in order to provide the correct gear ratio. In an automatic transmission, however, the gears are never physically moved and are always engaged to the same gears. This is accomplished through the use of planetary gear sets. The basic planetary gear set consists of a sun gear, a ring gear and two or more planet gears, all remaining in constant mesh. The planet gears are connected to each other through a common carrier which allows the gears to spin on shafts called “pinions“ which are attached to the carrier. One example of a way that this system can be used is by connecting the ring gear to the input shaft coming from the engine, connecting the planet carrier to the output shaft, and locking the sun gear so that it can't move. In this scenario, when we turn the ring gear, the planets will “walk“ along the sun gear (which is held stationary) causing the planet carrier to turn the output shaft in the same direction as the input shaft but at a slower speed causing gear reduction (similar to a car in first gear). If we unlock the sun gear and lock any two elements together, this will cause all three elements to turn at the same speed so that the output shaft will turn at the same rate of speed as the input shaft. This is like a car that is in third or high gear. Another way that we can use a Planetary gear set is by locking the planet carrier from moving, then applying power to the ring gear which will cause the sun gear to turn in the opposite direction giving us reverse gear. The illustration on the right shows how the simple system described above would look in an actual transmission. The input shaft is connected to the ring gear (Blue), The Output shaft is connected to the planet carrier (Green) which is also connected to a “Multi-disk“ clutch pack. The sun gear is connected to a drum (yellow) which is also connected to the other half of the clutch pack. Surrounding the outside of the drum is a band (red) that can be tightened around the drum when required to prevent the drum with the attached sun gear from turning. The clutch pack is used, in this instance, to lock the planet carrier with the sun gear forcing both to turn at the same speed. If both the clutch pack and the band were released, the system would be in neutral. Turning the input shaft would turn the planet gears against the sun gear, but since nothing is holding the sun gear, it will just spin free and have no effect on the output shaft. To place the unit in first gear, the band is applied to hold the sun gear from moving. To shift from first to high gear, the band is released and the clutch is applied causing the output shaft to turn at the same speed as the input shaft. Many more combinations are possible using two or more planetary sets connected in various ways to provide the different forward speeds and reverse that are found in modern automatic transmissions. Some of the clever gear arrangements found in four and now, five, six and even seven and eight-speed automatics are complex enough to make a technically astute lay person's head spin trying to understand the flow of power through the transmission as it shifts from first gear through top gear while the vehicle accelerates to highway speed. On modern vehicles (mid '80s to the present), the vehicle's computer monitors and controls these shifts so that they are almost imperceptible. Clutch PacksA clutch pack consists of alternating disks that fit inside a clutch drum. Half of the disks are steel and have splines that fit into groves on the inside of the drum. The other half have a friction material bonded to their surface and have splines on the inside edge that fit groves on the outer surface of the adjoining hub. There is a piston inside the drum that is activated by oil pressure at the appropriate time to squeeze the clutch pack together so that the two components become locked and turn as one.One-Way Clutch A one-way clutch (also known as a “sprag“ clutch) is a device that will allow a component such as ring gear to turn freely in one direction but not in the other. This effect is just like that of a bicycle, where the pedals will turn the wheel when pedaling forward, but will spin free when pedaling backward. A common place where a one-way clutch is used is in first gear when the shifter is in the drive position. When you begin to accelerate from a stop, the transmission starts out in first gear. But have you ever noticed what happens if you release the gas while it is still in first gear? The vehicle continues to coast as if you were in neutral. Now, shift into Low gear instead of Drive. When you let go of the gas in this case, you will feel the engine slow you down just like a standard shift car. The reason for this is that in Drive, a one-way clutch is used whereas in Low, a clutch pack or a band is used.BandsA band is a steel strap with friction material bonded to the inside surface. One end of the band is anchored against the transmission case while the other end is connected to a servo. At the appropriate time hydraulic oil is sent to the servo under pressure to tighten the band around the drum to stop the drum from turning. Torque ConverterOn automatic transmissions, the torque converter takes the place of the clutch found on standard shift vehicles. It is there to allow the engine to continue running when the vehicle comes to a stop. The principle behind a torque converter is like taking a fan that is plugged into the wall and blowing air into another fan which is unplugged. If you grab the blade on the unplugged fan, you are able to hold it from turning but as soon as you let go, it will begin to speed up until it comes close to the speed of the powered fan. The difference with a torque converter is that instead of using air, it uses oil or transmission fluid, to be more precise.A torque converter is a large doughnut shaped device (10“ to 15“ in diameter) that is mounted between the engine and the transmission. It consists of three internal elements that work together to transmit power to the transmission. The three elements of the torque converter are the Pump, the Turbine, and the Stator. Thepump is mounted directly to the converter housing which in turn is bolted directly to the engine's crankshaft and turns at engine speed. The turbine is inside the housing and is connected directly to the input shaft of the transmission providing power to move the vehicle. The stator is mounted to a one-way clutch so that it can spin freely in one direction but not in the other. Each of the three elements have fins mounted in them to precisely direct the flow of oil through the converter With the engine running, transmission fluid is pulled into the pump section and is pushed outward by centrifugal force until it reaches the turbine section which starts it turning. The fluid continues in a circular motion back towards the center of the turbine where it enters the stator. If the turbine is moving considerably slower than the pump, the fluid will make contact with the front of the stator fins which push the stator into the one way clutch and prevent it from turning. With the stator stopped, the fluid is directed by the stator fins to re-enter the pump at a “helping“ angle providing a torque increase. As the speed of the turbine catches up with the pump, the fluid starts hitting the stator blades on the back-side causing the stator to turn in the same direction as the pump and turbine. As the speed increases, all three elements begin to turn at approximately the same speed. Since the '80s, in order to improve fuel economy, torque converters have been equipped with a lockup clutch (not shown) which locks the turbine to the pump as the vehicle speed reaches approximately 45 - 50 MPH. This lockup is controlled by computer and usually won't engage unless the transmission is in 3rd or 4th gear.Hydraulic SystemThe Hydraulic system is a complex maze of passages and tubes that sends transmission fluid under pressure to all parts of the transmission and torque converter. The diagram at left is a simple one from a 3-speed automatic from the '60s. The newer systems are much more complex and are combined with computerized electrical components. Transmission fluid serves a number of purposes including: shift control, general lubrication and transmission cooling. Unlike the engine, which uses oil primarily for lubrication, every aspect of a transmission's functions is dependant on a constant supply of fluid under pressure. This is not unlike the human circulatory system (the fluid is even red) where even a few minutes of operation when there is a lack of pressure can be harmful or even fatal to the life of the transmission. In order to keep the transmission at normal operating temperature, a portion of the fluid is sent through one of two steel tubes to a special chamber that is submerged in anti-freeze in the radiator. Fluid passing through this chamber is cooled and then returned to the transmission through the other steel tube. A typical transmission has an average of ten quarts of fluid between the transmission, torque converter, and cooler tank. In fact, most of the components of a transmission are constantly submerged in fluid including the clutch packs and bands. The friction surfaces on these parts are designed to operate properly only when they are submerged in oil.Oil PumpThe transmission oil pump (not to be confused with the pump element inside the torque converter) is responsible for producing all the oil