transmission choices hj47 + h42 + h55 + fairey (1 Viewer)

Feb 13, 2008
surf coast, Australia
Hello All, I am in the process of doing some repairs to my HJ47 Troopy, the roof and sides are off and the head as been reco etc. My old 4 speed had some semi nasty bearing noise for the last 2 years and the gear float is now out of tolerance. I am almost certain that the bearing noise was the input->main shaft roller bearings (noise practically went away in 4th (input:main is 1:1) and was loudest in R and 1st (input:main is -4.3 or 3.5:1), this was tested with the T/Case in neutral, so I assume the noise is not from the T/Case. Gearbox still changed well and didn't jump out of gear.

Anyway I am probably going to buy a second hand 5 speed + fairey OD from a HJ60 this weekend because I want to get better hwy rpm. The possible combinations I have are 4sp + F, 5sp + No F or 5sp +F. From memory the 2H with standard wheels in 4th gear sat on about 2800rpm at 100 km/h (screaming its titties off!). 4th in the h42 is 1:1, the 5th gear in the H55f is 1:0.845 and the Fairey in OD is 1:0.787 (1:1 not engaged). Which gives me this table (assuming I was correct with 2800rpm at 100km/h)

100km/h 120 km/h​
4th | 2800rpm 3360rpm
5th | 2366 2840
4th+F | 2204 2645
5th+F | 1862 2234

I want advice to make the best educated choice given my possibilities. The downsides to keeping the 4 speed is have to at least replace the input shaft and input->main shaft bearings, and perhaps put in new thickness circlips to address the out of tolerance float. The downside to putting in the 5 speed is I will have to change shaft lengths and adjust the floor cover panel, and I don't know the condition of it. The downside to the fairey is it's ancient with no spare parts and I lose the transmission parking brake.

At the moment I am leaning towards putting the whole new transmission (5speed + F) in and changing shafts. But 1862 rpm at 100km/h is probably overkill. I guess I can drive around in 4th + F a lot of the time. Also having an extra stick in the floor would be fun (which is totally the wrong reason to want an OD).

What would you do?


Jul 8, 2013
New South Wales, Australia
I would be somewhat wary of the Fairey, I understand it can be difficult to get parts for them, although there is something cool about lots of gear sticks.
Also, you might find yourself going back gears for hills - easier to have 1 gear stick to shift (unless you've got 3 arms)
Hope some of this makes sense.

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