XK150 FHC Tremec T5 gearbox conversion project
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My T5 conversion project began in September 2014, nearly a year after I had purchased my 1958 XK150 FHC in October 2013.

My car had its original gearbox and overdrive, and I had receipts from the prior owner that showed the gearbox had been dismantled and fitted with new seals and bearings during the car's full restoration by that owner in 1998-99.

A long 2000km return trip to Melbourne from Sydney for the April 2014 Jaguar National Rally was proof enough that both the gearbox and the overdrive were in excellent condition regarding basic function, noise level and vibration. The synchro effectiveness of the second and third gears was about what could be expected for a Moss gearbox that had been in service for 100,000 miles. However, the gearbox had two major faults which had to be repaired:

  • Occasionally becoming jammed in first gear
  • Never ending oil leak from the rear extension of the gearbox

I decided for two reasons to fit a Tremec T5 gearbox in the car, and to later rebuild the Moss gearbox to fix the jamming fault and the chronic oil leak.

  • I use my XK150 regularly, and the car is fully registered for normal use, not just club events. I live in an area of Sydney which is hilly, and the lack of first gear synchro is a real problem, when combined with the impatience of the majority of modern drivers. So a full-synchro box was, for me, a major plus.
  • I did not want my car to be off the road for a long time.

In October 2014, I ordered a T5 conversion kit from a supplier in England. The kit arrived in Sydney early March 2015, but it was not until mid-May 2015 that the conversion was fully completed. There were some hiccups along the way, which could have been avoided if there had been some instructions in the kit. In the web pages to follow, more details are provided. Hopefully, my experience will be of use to others contemplating a similar project.

An extensive discusion the history of the T5 gearbox is available here.

The XK150 with its T5 full-synchro box is a delight to drive. A 600km return trip to Canberra in July 2015 proved that the ratios selection choice was sound. In regular local driving, the first gear synchro is a blessing. However, at some point in the future, the original Moss gearbox and overdrive will go back into the car!   


5-speed gearbox choices

Ratio selection

Other parts needed

Preparing the gearbox

Preparing the XK150 body for the change

Installation tips

Gear lever and adapter modifications

Which oil?

Reflecting: Was it worth it?

Gear lash - T5 vs Moss

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