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  American Powertrain Unveils New Ratios For TR-3650 Transmission

  Aug 17, 2010
  By:  All Ford Mustangs News Desk

American Powertrain is set to unleash a rebuild of the venerable TR-3650 5-speed transmission that closes up the gearing and opens up a world of power possibilities. The Tremec transmission is standard equipment on Mustang GTs from 2005, and is a direct swap for the more common T45. If you’re looking for a little extra stir in your stick, this might be right up your alley.


The stock TR-3650 is a five-speed box with a 3.38 to 1 first gear and a 0.68 or 0.62 overdrive fifth. The torque cap is 360 ft/lbs. Drag racers -- and guys who like to get a good jump off the light -- know a taller tail is best for quick getaways. But the standard 3.38 first winds out almost instantly with anything more than a 3.73 rear gear. It’s almost as well to start in the 2.00 to 1 second gear.

American Powertrain’s version offers a 2.90 first, a closer range to the 0.57 or 0.53 fifth, and new gearsets capable of taking on an 800-horsepower engine. With the closer gear ratios, they say, higher rpm shifting will be easier and more consistent.

As tech support “guru” Richard stated on the All Ford Mustangs forum, “It is an entirely different second to fourth gear kit that can be placed in either the 2001-2004 or the 2005 and up 3650's and will support up to 800hp. Plus, it will convert the 1st gear ratio to a 2.90! The overdrive is modified due to the different tooth count on the gears, which actually makes 5th gear either a .57 or a .53 depending on your current overdrive in the factory transmission. If your stock 3650 has the .67 5th, with our new gear set, you would end up with a .57, if your current O/D is the .62, you would end up with a final ratio of .53!”

The upgrade also makes necessary a 26-spline clutch disc, as the input is only available in 26-spline configuration to be able to support 800 hp without twisting the splines. But the stock bell housing, shifter, cross member and driveshaft are reused.

These will be ground cut gears so they will be a little more noisy than the OE transmission -- hey, some of us like a little mechanical noise in our machines -- but American Powertrain plans on introducing a helical cut gear in the near future which would reduce the noise to OE levels.

A warranty will be available, and although prices are not yet set, Richard advises, “We are still working out the details but figure $2500. In the scheme of things, putting a TKO in your car would run you about $2800+ and it is not as strong as this is going to be and with the preferred gear ratios of the new 3650, it's a win win situation for everyone.”

For more info, visit the American Powertrain website.

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