TR3650 Transmission Tech Specs, Gear Ratios, & More

TR3650 Transmission Tech Specs

The Ford Mustang is arguably one of the most liked cars in the world. Ford captured the hearts and imaginations of millions across the globe with one of the most iconic lines of cars they ever built. But rarely do you hear about the inner workings of such cars past just the aesthetic value and horsepower. Today, we pay homage to the transmission that supported some of our beloved Mustangs from the early 2000s to 2010.

First fitted in 2001 for the Mustang GT and Cobra, the TR3650 was a Tremec-built five-speed manual transmission. It would later find application in the Ford Mustang Bullit, 2003 to 2004 Ford Mustang Mach l, and the Ford Falcon.

Built to replace the T-45 5-speed, Ford was in need of a hardier gearbox that could handle more torque and they chose Tremec for the design. Among the improvements, the TR3650 came with was a fortified 11-inch clutch disc, a step up from the T-45’s 10.5”.

First generation TR3650s produced from 2001 to 2004 came with a cable-operated clutch fork and traditional throwout bearing, while the 2005 to 2010 models were upgraded to a hydraulic throwout sitting on the input shaft. Other modifications included a body-mounted shifter from previous transmission-mounted ones and a tail shaft design moved to a fixed flange from a slip-yoke.

TR3650 Gear Ratios

The TR3650 ratios were as follows:

  • One – 3.38
  • Two – 2.00
  • Three – 1.32
  • Four – 1.00
  • Five – 0.67 for 2001, and 0.62 from 2002 to 2004
  • Reverse – 3.38

The 2002 Ford Australia had slightly different modified TR3650 ratios:

  • One – 3.37
  • Two – 2.00
  • Three – 1.32
  • Four – 1.00
  • Five – 0.62
  • Reverse – 3.77

Other technical specifications for the TR3650 include an aluminum casing, an input shaft with ten splines, a 31-spline output rod, and a weight of 119 lbs.

Tremec TR3650 Fluid Capacity 

The TR3650’s fluid capacity sat at 3.6L or 7.6 pt.

Type of Fluid Needed for Proper Operation

Engineers recommend the Tremec TR3650 be used with the Mercon XT2 QDX (non-synthetic ATF) or the Texaco-Havoline Dexron lll. However, there has been some contradiction in the TR3650 community with some fluids rumored to cause noisy synchros, rough shifting, and gear grinding. This uncertainty is further perpetuated by different owner’s manuals recommending different fluids for cars with the same transmission.

The ’07 Mustang GT’s manual says three liters of non-synthetic Mercon ATF, and the 2008 Mustang GT reads Mercon-V ATF fluid. The pre-’05 Mustangs seem to work well with Dexron lll or Mercon non-synthetic ATF. To add even more to the confusion, Tremec engineers have also touted the GM Synchromesh.

TR3650 parts are fairly easy to get with complete rebuild kits with synchro rings, bearings, seals, and gaskets going for $437 on various online sources. On eBay, you can even get one for $360.

Factory torque handling capability

The TR3650 was built as an upgrade to the t-45 and boasted more torque handling capability. Different versions of the transmission had different torque capabilities, between 360 and 390 lbs-ft.

  • 360 lbs-ft – TR3650, TR3650-1, TR3650-3, TR3650-4, TR3650-5, TR3650-6
  • 390 lbs-ft – TR3650-2

Common TR3650 Issues

Separator plate buzzing sound. The 2005 to 2008 Ford Mustang 4.6 produced a buzzing sound while the vehicle was still not warmed up. The solution was to replace the separator plate.

Grinding noise and hardship make the one to two shifts. This was especially infamous in the ’04 Ford Mustang 4.6 but also affected other TR3650s. Drivers would experience a grinding noise when making the shift from one to two. It would also be hard to make this shift, with some drivers reporting the gear would pop out as soon as their feet left the clutch. However, it’s not a problem. Some GT owners say the shifter is especially sublime when shifting out of second and sometimes first. Just give it a light nudge and it jumps right out. Changing the 1-2 synchronizer assembly, synchro rings & cones, and 1-2 shift fork plus rail would solve this.

The Bullitt Mustang too had transmission problems. Somehow, all the other cars’ issues seemed to culminate in the Bullitt. Under intense acceleration, it would pop out of gear and, if left unattended for a few weeks, would not engage even with the pedal on the floor and the vehicle at standstill. Bent 1-2 forks and a bad synchro are usually to blame here. Replacement should solve this problem.

The 2005 to 2009 Mustangs were especially sensitive to these issues and the transmission would deteriorate very quickly if left unchecked. The symptoms start with a gear grind in reverse, then moves to the two to three shift, and finally the three to four shift. When it gets to this point, your 3-4 synchro is gone along with your blocking ring; the third, fourth, and reverse gears are also damaged. At this point, the repairs will usually be more than most shops’ rebuilding caps and they will have to put a new transmission in.

When looking for a TR3650 transmission for sale there are a few things to consider. Are you looking for a new one or a remanufactured one? A remanufactured can cost you $2390, you can get one with a three-year warranty for that price. For a used or rebuilt one, $1,000 with a $400 core deposit is common and if you are lucky enough to get it on sale or at a discount, figures as low as $780 are possible.