Toyota plans to have a 4.6L 1UR engine available on the 2010 Tundra, as well as a new 6spd automatic transmission for the 4.6 motors.



"Toyota is stating the new V-8’s specs at 310 horsepower at 5,600 rpm and 327 pounds-feet of torque at 3,400 rpm. Although these numbers may not sound hugely impressive -- especially compared with its direct competitors -- this new engine does offer the best horsepower and torque for its size, especially when you look at horsepower and torque per liter.

As for fuel economy -- an all-important number nowadays -- EPA numbers haven’t been finalized, but Toyota is saying the numbers will be as good as, if not better than, the leading V-8 numbers in the class, which means upward of 15 or 16 mpg in the city and a minimum of 20 mpg on the highway. These numbers are most likely for the regular cab, short-bed, two-wheel-drive model.

This new engine isn’t the only trick up Toyota’s sleeve; along with the new V-8, the automaker also has a “new” six-speed transmission (the A760E). Some might have guessed Toyota would use the six-speed it already pairs with its 5.7-liter V-8, but after considerable testing engineers concluded that transmission wasn’t a perfect match for the horsepower and torque output of the smaller V-8. Instead, they decided to slightly modify the gear ratios of the existing five-speed auto and include another cog without having to increase the size or weight of the transmission itself. As a result, 1st gear is a respectable 3.52:1 and 6th gear is a low-rpm-running 0.59:1. Preliminary fuel economy numbers are calculated with the lower (numerically) of the two ring-and-pinion gearsets offered (3.91:1 and 4.10:1). We’re guessing Toyota is leaving itself plenty of room for a possible high-mileage option package down the road, possibly offering 3.55:1 or 3.73:1 axle gear options. Some major players in the segment are using 3.15:1 gears for their high-mpg packages."



More info here:
http://special-reports.pickuptrucks....ive-video.html

Also found on Toyota's website:
http://www.toyota.com/about/news/pro...-1-tundra.html



This appears to be another version of the 1UR motor. Toyota has two other version of the 1UR. The GS460 has a 1UR-FE making 342hp, and the LS460 has a 1UR-FSE (direct injection) making 380hp.

This motor should also be available as an option in the Sequoia, and I think it is vary likely to be an option on the 5th gen 4Runner.