R154 Technical Writeup

Technical write up on the Toyota R154 gearbox.

Toyota R154 Specifications and Details

R154The R154 is made by Toyota, Japan. It’s a 5 speed gearbox (5 forward gears + reverse). As with most Toyota driveline components, the R154 is of quality design and construction. Unfortunately as always seems to be the case with modern technology, there is always an Achilles heal.

The R154 is a conventional 5-speed gearbox, with 5 forward gears and a straight-cut reverse gear. The reason for the strength of the gearbox is plain to see even by the naked eye. The external casing and the gears themselves are credibly sized for a performance-oriented gearbox.

The weak point, however, is the first gear thrust washer. Being of a cast construction, this part is prone to failure if the box is maltreated. In most known cases this is a result of one (or a combination of!) three things:

  • abuse or misuse of the gearbox
  • when the gearbox is used with a high-clamp and/or button clutch
  • big-horsepower applications

The easiest fix for this weakness is to lighten up on the gearbox and treat it with respect. For gearbox owners with less self-control, the best option is to have the gearbox broken down and reassembled with a new thrust washer made of chromoly for added strength.

The part itself is quite inexpensive (around AUD$26.50), however the damage it can cause in the event of failure is quite humbling. The first gear bearing takes the brunt of this failure due to being located in front of the thrust washer.

thrust washer 1 thrust washer 2 thrust washer 3 thrust washer 4 thrust washer 5 thrust washer 6

In more severe failures, or if the car continues to be driven after a failure, one or more of the gears will need to be replaced. First gear alone has been priced at AUD$550. Certainly not a cheap exercise, and one better avoided.

In a perfect world the ideal solution is to replace the R154 with a V16x gearbox from a Mk4 Supra. These are much stronger and more widely proven behind big-horsepower 2JZ engine combinations.

Manual Transmission Specifications

Gear                              Ratio                  Km Per 1000rpm
First                               3.251                     9.6
Second                           1.955                    16.0
Third                             1.310                    24.0
Fourth                           1.000                   31.4
Fifth                               0.753                    41.7
Reverse                         3.18

Final Drive                    3.727 (Mechanical LSD)

Lubricant Capacity      3 Litres
Oil Specifications          80W-90 GL4 or 5 Gear Oil

Dry Weight                    46kg

R154 - case removed 4 R154 - case removed 5 R154 - case removed 3 R154 - case removed 2 R154 - case removed 1

  • Length – Bell housing to Out put shaft
  • Length – Bell housing to End case
  • Length – Bell housing to Centre of Shifter
  • Width – Bell housing
  • Width – Gear Case (maximum)
  • Height – Bell housing
  • Height – Gear Case (maximum)
  • Input Shaft OD     30mm
  • Drive Plate Diameter     245mm
  • Drive plate surface area     40mm