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Aisin AX15 vs TREMEC TR-4050

The Aisin AX15 5-Speed Transmission History

This 5-speed was used in Jeeps equipped with the AMC 242 4.0L Inline 6 and AMC 258 4.2L Inline 6 engines. Jeep put them in several different vehicles, including the Cherokee (XJ), Comanche (MJ), Wagoneer, and both the YJ and TJ models of the Wrangler from mid-1988 to 1999.

The TREMEC TR-4050 5-Speed Transmission History

First introduced in the early 90's the TR-4050 5-Speed was a favorite of Chevrolet, Ford, and Dodge for applications that required a heavy-duty transmission. This aftermarket version of the TREMEC transmission is the result of a partnership between TREMEC and Silver Sport Transmissions to fill the need of the off-road enthusiast market and was launched in 2019. 


Aisin AX15 vs TREMEC TR-4050 by the Numbers


Gear Ratios

AX15 vs TR-4050 Gear Ratio Table

The TR-4050's 1st gear and reverse are almost twice as low as the AX15's. The advantage here is the ability to slow down the wheels and transfer more engine power to climb or descend steep terrain and large boulders or crawl through the slick mud. The TR-4050 has a comparable 5th overdrive gear for highway use so you're really just exchanging an extra roll around town gear for a gear that can take you further.


Torque Ratings

AX15 - We couldn't find authoritative numbers for the AX15's torque capacity. The max torque output of the 4.0L and 4.2L engines was about 220-235 lb-ft so the 275-300 lb-ft torque capacity estimate we found mentioned in 4WD forums by transmission builders is probably pretty accurate although real-world application varied. A used and abused AX15 may not have the same torque capacity it once had when it was brand new which could explain why some people with 300 lb-ft torque output engines were still able to break the AX15.

TR-4050 - The TR-4050 is a brand new transmission, fresh off the assembly line, and is rated at 600 lb-ft continuous input torque. More than enough if you're going to swap out your old I6 for an LS or Gen 3 HEMI. It is the strongest 4WD transmission available in the aftermarket.


TREMEC TR-4050 Spec Sheet

  • 600 lb•ft Torque Capacity
  • Brand new transmission, not rebuilt or remanufactured
  • Right Side PTO - 6 bolt offers the ability to run hydraulic pumps
  • High-contact constant-mesh helical gears for maximum strength
  • Die-cast aluminum alloy housing saves weight while offering considerable rigidity
  • Multi-rail shift linkage provides excellent shift feel and performance
  • Tapered bearing on input, main and counter shafts provide excellent internal stability
  • Needle bearings under gears reduce friction and noise output
  • All forward gears and reverse gear synchronized
  • Advanced synchronizer technology promotes smoother shifting and reduced shift effort
  • Countershaft mounted 5th gear synchronizer improves noise, vibration, and harshness in overdrive


Complete Kits Available

We have conversion kits for several makes and models. Choose an application below to see if we have a complete kit for your 4WD.

Choose an Application

Cummins Ford GM Jeep Land Rover Mopar

Cummins Diesel

  • 4BT
  • 6BT
  • R2.8
  • 5.0


  • 289, 302, 351
  • I6 - 240, 300
  • Modular V8

General Motors

  • SBC
  • BBC
  • LS
  • LT
  • 3rd Gen I6

AMC / Jeep

  • I6 - 232, 242, 258
  • V8 - 304, 360, 410

Land Rover

  • Defender

Dodge / Mopar / RAM

  • V8 - 318, 340, 360
  • Gen III Hemi


Don't see your vehicle? Give us a call to discuss your options.