Safety apparatus in an automatic transmission for a vehicle to prevent engagement of the low speed clutch at high speeds

In an automatic transmission apparatus for a vehicle of the type having a high speed clutch of an oil pressure operated type interposed in a high speed power transmission system and a low speed clutch of an oil pressure operated type interposed in a low speed power transmission system, a shift valve, the clutches being selectively connected through said shift valve to an oil pressure source, said low speed clutch being provided with an oil pressure chamber connectible to the pressure source, a safety apparatus comprising an automatic control valve coupled to said low speed clutch having a valve chamber in communication with said oil pressure chamber, said valve chamber having an outlet for relieving pressure in said oil pressure chamber, and a speed responsive valve member in said valve chamber for selectively opening said outlet thereof when the speed of rotation of the low speed clutch reaches a predetermined value;

• and said high speed clutch having a pressure chamber, said apparatus further comprising means connected to said outlet and to said pressure chamber of the high speed clutch for supplying pressure fluid fed to the low speed clutch to said high speed clutch when said automatic control valve is open.