Multi-speed transmission

1. A transmission comprising:

an input member;

an output member;

first, second, third, and fourth planetary gear sets each having first, second, and third members;

a first torque transmitting mechanism selectively engageable to interconnect the input member with the first member of the second planetary gear set;

a second torque transmitting mechanism selectively engageable to interconnect the third member of the fourth planetary gear set with at least one of the third member of the first planetary gear set and the third member of the second planetary gear set;

a third torque transmitting mechanism selectively engageable to interconnect the second member of the first planetary gear set with the third member of the fourth planetary gear set;

a fourth torque transmitting mechanism selectively engageable to interconnect the second member of the fourth planetary gear set with at least one of the third member of the first planetary gear set and the third member of the second planetary gear set; and

a fifth torque transmitting mechanism selectively engageable to interconnect the second member of the fourth planetary gear set with the third member of the third planetary gear set, and

wherein a plurality of combinations of two torque-transmitting mechanisms are disengaged to establish at least eight forward speed ratios and at least one reverse speed ratio between the input member and the output member.

2. The transmission of claim 1 wherein one of the at least one reverse speed ratios is achieved by engagement of the first, fourth, and fifth torque transmitting mechanisms.

3. The transmission of claim 2 wherein a first of the at least eight forward speed ratios is achieved by engagement of the first, second, and fifth torque transmitting mechanisms.

4. The transmission of claim 3 wherein a second of the at least eight forward speed ratios is achieved by engagement of the first, third, and fifth torque transmitting mechanisms.

5. The transmission of claim 4 wherein a third of the at least eight forward speed ratios is achieved by engagement of the second, third, and fifth torque transmitting mechanisms.

6. The transmission of claim 5 wherein a fourth of the at least eight forward speed ratios is achieved by engagement of the third, fourth, and fifth torque transmitting mechanisms.

7. The transmission of claim 6 wherein a fifth of the at least eight forward speed ratios is achieved by engagement of the second, fourth, and fifth torque transmitting mechanisms.

8. The transmission of claim 7 wherein a sixth of the at least eight forward speed ratios is achieved by engagement of the second, third, and fourth torque transmitting mechanisms.

9. The transmission of claim 8 wherein a seventh of the at least eight forward speed ratios is achieved by engagement of the first, second, and fourth torque transmitting mechanisms.

10. The transmission of claim 9 wherein an eighth of the at least eight forward speed ratios is achieved by engagement of the first, third, and fourth torque transmitting mechanisms.

11. The transmission of claim 1 wherein the third member of the first planetary gear set is continuously interconnected with the third member of the second planetary gear set, the second member of the second planetary gear set is continuously interconnected with a stationary element, the second member of the second planetary gear set is continuously interconnected with the first member of the first planetary gear set, and the first member of the third planetary gear set is continuously interconnected with the first member of the fourth planetary gear set.

12. The transmission of claim 1 wherein the first members are sun gears, the second members are carrier members, and the third members are ring gears.

13. The transmission of claim 1 wherein each of the torque transmitting mechanisms is engaged in at least five of the speed ratios.

14. A transmission comprising:

an input member;

an output member;

first, second, third, and fourth planetary gear sets each having sun, carrier, and ring members;

at least four continuous interconnections from at least one of the sun members, the carrier members, the ring members, and a stationary member to at least one other of the sun, carrier, and ring members;

a first torque transmitting mechanism selectively engageable to interconnect the input member with the sun member of the second planetary gear set;

a second torque transmitting mechanism selectively engageable to interconnect the ring member of the fourth planetary gear set with at least one of the ring member of the first planetary gear set and the ring member of the second planetary gear set;

a third torque transmitting mechanism selectively engageable to interconnect the carrier member of the first planetary gear set with the ring member of the fourth planetary gear set;

a fourth torque transmitting mechanism selectively engageable to interconnect the carrier member of the fourth planetary gear set with at least one of the ring member of the first planetary gear set and the ring member of the second planetary gear set; and

a fifth torque transmitting mechanism selectively engageable to interconnect the carrier member of the fourth planetary gear set with the ring member of the third planetary gear set, and

wherein a plurality of combinations of at least three engaged torque-transmitting mechanisms and at least two disengaged torque-transmitting mechanisms establish at least eight forward speed ratios and at least one reverse speed ratio between the input member and the output member.

15. The transmission of claim 14 wherein the first torque transmitting mechanism is engaged in at least a first, second, seventh, and eighth of the at least eight forward speed ratios and at least one of the at least one reverse speed ratio.

16. The transmission of claim 14 wherein the second torque transmitting mechanism is engaged in at least a first, third, fifth, sixth, and seventh of the at least eight forward speed ratios.

17. The transmission of claim 14 wherein the third torque transmitting mechanism is engaged in at least a second, third, fourth, sixth, and eighth of the at least eight forward speed ratios.

18. The transmission of claim 14 wherein the fourth torque transmitting mechanism is engaged in at least a fourth, fifth, sixth, seventh, and eighth of the at least eight forward speed ratios and at least one of the at least one reverse speed ratio.

19. The transmission of claim 14 wherein the fifth torque transmitting mechanism is engaged in at least a first, second, third, fourth, and fifth of the at least eight forward speed ratios and at least one of the at least one reverse speed ratio.

20. A transmission comprising:

an input member;

an output member;

first, second, third, and fourth planetary gear sets each having first, second, and third members, wherein the input member is interconnected with the second member of the third planetary gear set and the output member is interconnected with the third member of the third planetary gear set;

a selectively engaged reverse torque transfer path including the first member of the second planetary gear set interconnected with the input member and the third members of the first and second planetary gear sets interconnected with the second member of the fourth planetary gear set and the third member of the third planetary gear set;

a selectively engaged first torque transfer path including the first member of the second planetary gear set interconnected with the input member, the third members of the first and second planetary gear sets interconnected with the third member of the fourth planetary gear set, and the second member of the fourth planetary gear set interconnected with the third member of the third planetary gear set;

a selectively engaged second torque transfer path including the first member of the second planetary gear set interconnected with the input member, the third member of the fourth planetary gear set interconnected with the second member of the first planetary gear set, and the second member of the fourth planetary gear set interconnected with the third member of the third planetary gear set;

a selectively engaged third torque transfer path including the third members of the first and second planetary gear sets interconnected with the third member of the fourth planetary gear set and the second member of the first planetary gear set, and the second member of the fourth planetary gear set interconnected with third member of the third planetary gear set;

a selectively engaged fourth torque transfer path including the third members of the first and second planetary gear sets interconnected with the second member of the fourth planetary gear set and the third member of the third planetary gear set, and the second member of the first planetary gear set interconnected with the third member of the fourth planetary gear set;

a selectively engaged fifth torque transfer path including the third members of the first and second planetary gear sets interconnected with the second member of the fourth planetary gear set and the third member of the third and fourth planetary gear sets;

a selectively engaged sixth torque transfer path including the third members of the first and second planetary gear sets interconnected with the second member of the first planetary gear set and the second and third members of the fourth planetary gear set;

a selectively engaged seventh torque transfer path including the first member of the second planetary gear set interconnected with the input member, and the third members of the first and second planetary gear sets interconnected with the second and third members of the fourth planetary gear set; and

a selectively engaged eighth torque transfer path including the first member of the second planetary gear set interconnected with the input member, the second member of the first planetary gear set interconnected with the third member of the fourth planetary gear set, and the third members of the first and second planetary gear sets interconnected with the second member of the fourth planetary gear set.