Up To Standards
- Author: Mike Weinberg, Contributing Editor
The only constant in our business is change. The competition for market share and the rapid growth of new technology keep us busy just learning the new components being introduced in the cars we work on.
The venerable Mustang is still the performance vehicle of choice for Ford Motor Co., and Ford has upgraded the driveline with two transmissions that are new to the company. The Mustang comes equipped with a 4.6-liter “modular” engine with either two or four valves per cylinder. For 2003 models the two-valve engines are coupled with a TR3650 5-speed manual transmission, and the four-valve engines use a T56 6-speed manual transmission.
The T56 is not new, having been used for years by General Motors in the F-body (Camaro/Firebird) cars and the Corvette and by Daimler/Chrysler in the mighty Viper model. The TR3650 was introduced into the Mustang in 2001 and continues in use behind the two-valve 4.6-liter engine. New in 2003 is the T56 model. This article will concentrate on the TR3650.
The TR3650 is manufactured by Tremec Corp., a state-of-the-art transmission manufacturer with facilities in the United States and Mexico. Tremec bought the standard-transmission line from BorgWarner Corp. and continues to manufacture the T5, T45, TR3550, TKO and T56 transmissions.
You can trace the design evolution through the Ford Mustang models. In developing the 5-speed manual transmission they started with the T5. The T45 then replaced the T5, and in 2001 models the TR3650 was introduced.
The TR3650 is a 5-speed manual transmission with an aluminum bellhousing, main case and extension housing. All forward gears are helical cut and synchronized with 5th being overdrive. The reverse gearset is fully synchronized and is in constant mesh. A shift interlock system prevents the driver from engaging more than one gear at a time. The 5th/reverse synchronizer assembly is mounted on the countershaft to make a more-compact design. The TR3650 weighs 120 pounds dry and is capable of handling 360 lb.-ft. of torque.
Ratios¬:
- 1st gear – 3.38-1
- 2nd gear – 2.00-1
- 3rd gear – 1.32-1
- 4th gear – 1.00-1
- 5th gear – 0.67-1
- Reverse – 3.38-1
A metal tag bolted to the extension housing contains a Ford part number, and a Tremec part number also identifies the unit. The Tremec part number will begin with 1381 followed by three zeroes, which indicate a complete transmission assembly, and the final three digits indicate the design level of the gearbox. See the identification chart included here.
This unit uses double-lined synchro rings for improved shifting, and the required lube fill is 7.5 pints of Mercon synthetic ATF. Using fluids other than those specified by Ford will lead to shift complaints and possible synchronizer damage or premature wear. As of this writing, parts had not been released to the aftermarket and must be obtained through the Ford dealer network. If you need to replace a unit because of extreme damage, a Tremec 3550 aftermarket performance unit is a direct bolt-in replacement, and for customers who wish a little more top-gear acceleration the TR3550-II unit is available with a 0.80 5th gear
This unit will be disassembled in a vertical position like the T45 and T56 units you are familiar with. A Ford service manual will make all the specifications and repair procedures available to you when you need to repair one of these gearboxes. The design changes in this transmission are not radical, and if you have worked on T45 and T56 units, you will find this to be very similar.