Legacy GT:Subaru Legacy (fourth generation)/Transmissions

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5EAT

The 5EAT/ 5AT is the most common transmission available in the 4th Gen LGT/ OBXT. Based on the Jatco 5R05, the 5EAT is a 5-speed, planetary-gear type automatic transmission. All variations of the 5EAT have an open front differential, an electronically controlled, VTD (Variable Torque Distribution), limited-slip center differential, and are paired with a viscous limited-slip rear differential. The center differential has a default torque-split of ~ 40%(F)/60%(R), but can adjust or lock itself as needed based on wheel slip. All models of the 5EAT are equipped with Subaru's "SportShift" tiptronic manual shifting system, which was co-developed with Prodrive. The 5EAT's stock converter stall speed is ~3000rpm. The 5EAT weighs ~210lbs.

A stock 5EAT can reliably support ~300-325whp without modification, but is susceptible to clutch-slip in high-torque applications. The addition of a secondary fluid-to-air transmission cooler improves the 5EAT's reliability considerably and provides increased reliable power capacity up to ~325-350whp, but clutch-slip will still be an issue in high-torque applications. Modifying the transmission's valvebody with a shift-improvement kit or valvebody modification service increases the reliable power capacity even further, up to ~425-475whp. With a valvebody modification, the 5EAT can achieve shift speeds as low as 150-175ms. (Note: There are currently no mods available for the '08+ model 5EAT valvebody.) With the addition of an external fluid cooler and a valvebody modification, the threat of clutch-slip is minimized, but the integrity of the center differential becomes the main failure point. The 5EAT's center differential is susceptible to shock loading (such as when launching the vehicle under boost), as well as large amounts of low/mid-range torque. Tuning and/ or careful driving to minimize shock/ torque loading on the transmission can greatly increase reliability.

The 5EAT, in regards to the 4th Gen LGT/ OBXT, has been released as two different model generations with three different variations among them. The model generations are split between the '05-'07 model years and the '08-'09 model years. The '08-'09 received an updated 5EAT with improved shifting smoothness and drivability; although, as stated, there are currently no valvebody modifications available for this model. All variations of the 5EAT use the same gearset, but changes were made to the differential final-drive ratios through the years.

5EAT Gearset:

  • 1 - 3.54
  • 2 - 2.26
  • 3 - 1.47
  • 4 - 1.00
  • 5 - 0.83
  • R - 2.37

5EAT Final Drive Ratios:

  • 3.08 - 2008-2009 LGT
  • 3.27 - 2005-2007 LGT, 2007-2009 OBXT
  • 3.58 - 2005-2006 OBXT

Below is a table of top-speeds capable in each forward gear with each variation, as well as tach reading at 65mph in top gear. Using stock tire sizes (LGT-215/45r17, OBXT-225/55r17) and factory 6500rpm limter.

4th Gen LGT/ OBXT - Top Speeds - 5EAT
FD Ratio 1st (MPH) 2nd 3rd 4th 5th RPM @ 65mph
3.08 45 68 105 155 186 2280
3.27 (LGT) 42 64 99 146 175 2410
3.27 (OBXT) 46 70 108 158 191 2230
3.58 42 64 98 144 174 2410

5MT

The 5MT was released in ~30% fewer cars than the 5EAT across production of the 4th Gen LGT/ OBXT. The 5MT used in the LGT/ OBXT is an improved and beefed-up version of the 5MT used in the WRX, FXT, and NA models, using heavier gearsets comparable to the 6MT's gearsets, as well as a heavier case. Due to these improvements, the LGT/ OBXT's 5MT can reliably handle significantly more power than its weaker cousin. Like most 5MT models, the LGT/ OBXT 5MT uses an open front differential, a viscous 50%/50% limited-slip center differential, and is paired with a viscous limited-slip rear differential. The 5MT weighs ~150lbs.

With the stock clutch, the 5MT can reliably handle ~300-350whp. With an upgraded clutch and case reinforcements, reliable power capacity is increased to ~425-475whp. The failure point of the 5MT is most often the transmission case, which is prone to flexing and breaking under large amounts of torque. Much like the the 5EAT, tuning and/ or careful driving to minimize torque loading can greatly increase reliability.

The 5MT was released in three different variations in the 4th Gen LGT/ OBXT. All three variations use the same gearset, with changes to the final drive ratios.

5MT Gearset:

  • 1 - 3.17
  • 2 - 1.89
  • 3 - 1.30
  • 4 - 0.97
  • 5 - 0.74
  • R - 3.33

5MT Final Drive Ratios:

  • 3.90 - 2008-2009 LGT
  • 4.11 - 2005-2007 LGT
  • 4.44 - 2005-2009 OBXT

Below is a table of top-speeds capable in each forward gear with each variation, as well as tach reading at 65mph in top gear. Using stock tire sizes (LGT-215/45r17, OBXT-225/55r17) and factory 6500rpm limter.

4th Gen LGT/ OBXT - Top Speeds - 5MT
FD Ratio 1st (MPH) 2nd 3rd 4th 5th RPM @ 65MPH
3.90 39 65 94 126 165 2570
4.11 37 61 89 119 157 2700
4.44 37 62 90 120 157 2700

6MT

Only released in the 07-09 LGT-SpecB, with ~1000-1200 units being sold in the US, LGTs with factory 6MTs are hard to come by. The LGT's 6MT is based on the 6MT used in the '08-'18 STi, however, it was not released with the STI's DCCD and limited-slip front differential. Instead, the LGT's 6MT was released with a more-standard 50%/50% viscous limited-slip center differential, an open front differential, and was paired with a Torsen limited-slip rear differential. The 6MT weighs ~200lbs.

The 6MT is consensually agreed-upon to be the strongest transmission released by Subaru, even one of the best transmissions ever made. The stock clutch is, of course, a limiting factor right out of the gate. Without modification, the 6MT can handle ~300-350whp reliably. With an upgraded clutch, the 6MT can take significantly more power, upwards of ~500+whp reliably. Accounts of 6MTs holding well above 600whp are not uncommon. As with the LGT's other transmissions, tuning and/ or careful driving to minimize torque loading can greatly increase reliability.

The 6MT was only released in one configuration in the LGT. This is the same gearset used in the '08-'18 STi with a slightly taller top gear.

6MT Gearset:

  • 1 - 3.64
  • 2 - 2.24
  • 3 - 1.50
  • 4 - 1.14
  • 5 - 0.90
  • 6 - 0.71

6MT Final Drive Ratio:

  • 3.90 - 2007-2009 LGT SpecB

Below is a table of top-speeds capable in each forward gear with each variation, as well as tach reading at 65mph in top gear. Using stock tire size (LGT SpecB-215/45r18) and factory 6500rpm limter.

4th Gen LGT SpecB - Top Speeds - 6MT
FD Ratio 1st (MPH) 2nd 3rd 4th 5th 6th RPM @ 65mph
3.90 35 57 85 111 141 179 2360
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