2008 Lexus IS-F
2008 Lexus IS-F. Click image to enlarge

By Jim Kerr; photos by Chris Chase

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2008 Lexus IS F

Talk to most car enthusiasts, especially the sports car types, and you will find that a manual transmission is their overwhelming choice in transmissions. The positive control, quick shifts and deceleration driveline braking are all attributes they desire when demonstrating a vehicle’s performance. Now Lexus has introduced an automatic transmission than will not only do all the things a manual gearbox will do – it will do them faster and better.

Lexus has already introduced an eight-speed automatic in their large sedans, but now they have designed a high performance eight-speed automatic for their new 2008 IS F sports sedan. The more gears you have, the easier it is to keep the engine operating in its peak power or torque range. The big problem with having eight gears is that there is a time delay every time a shift occurs, where power is not applied to the drive wheels. Lexus has overcome that with the internal design of the transmission.

2008 Lexus IS-F
2008 Lexus IS-F. Click image to enlarge

When placed in Drive mode, the computer shifts the transmission like it was a conventional sports sedan. Light throttle applications give smooth almost imperceptible shifts. Move one of the paddle shifters and the transmission will upshift or downshift immediately if engine r.p.m. is within operating limits, and the system will revert back to full automatic mode in fifteen seconds if no further paddle shifter inputs are seen. The real performance starts when the driver places the transmission in M or manual mode.

Manual mode gives the driver full manual control of the transmission. The transmission uses planetary gearsets and clutches like most common automatic transmissions, but the Lexus IS F has large, high flow control solenoids to shift each gear. The rapid response of the solenoids and application of the clutches enables the transmission to upshift gears in only one-tenth of a second. This makes it among the quickest shifting automatic transmission on the streets, quicker than the Ferrari F430 and equal to the Ferrari 599 GTB.

The IS F computer will calculate the shift parameters in 0.2 seconds and then shift it in 0.1 second. Compare this to a conventional sports car automatic, where the computer can take 0.7 seconds to calculate the parameters and 0.6 seconds to complete the shift. I have never liked the manual mode in almost all automatics because they took as long to shift as if I had left the shifter in Drive. Now the Lexus IS F has made the shifts even more responsive than a good driver with a manual gearbox.

2008 Lexus IS-F
2008 Lexus IS-F. Click image to enlarge

The torque converter in an automatic transmission cushions the shift, which gives a mushy feel to the vehicle performance during a high performance shift. Lexus overcomes that by using the torque converter in manual mode only in first gear to allow the car to pull away from a stop. After that, the torque converter clutch remains applied at all times, locking the torque converter so there is no slippage and firm precise shifts.

Another feature of the gearbox is that the transmission does not automatically shift out of the selected gear when driving. Back off the throttle or rev it to red line and the transmission will remain in the same gear. The only time it will downshift automatically is if the selected gear is so high that it would cause the engine to stall. Then it will downshift a gear.

Finally, downshifting the IS F transmission is a lot easier than the old “heel and toe” routine that performance drivers do with the manual transmission pedals to keep the vehicle under the best control. The IS F does it all for you! When downshifting at higher engine rpm’s, the transmission computer will select neutral, blip the throttle to bring the engine rpm up to match driveline speed, downshift the transmission and apply the clutches for the gear – all in two tenths of a second. This ensures that the car’s tires don’t receive a shock from too much torque or too much engine braking that would upset the balance and handling of the car. This may not seem critical in a straight line, but when downshifting on a corner, any change in tire traction could send you off the road in a spin. The IS F downshift mode ensures this doesn’t happen because you selected a lower gear.

The hardware changes in this transmission are minimal but the software that is now applied to those small changes have allowed the IS F automatic transmission to become a world leader, besting even those manual gearboxes.

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