View single post by Tony Hollart
 Posted: 05-07-2007 11:27 am
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Tony Hollart

 

Joined: 03-21-2005
Location: Waitomo Caves, Otorohanga, New Zealand
Posts: 40
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 My aim was to get a slightly higher ratio in 4th gear, at 100 kmph my car pulls about 3400 rpm. This is  bit buzzy and I thought with a slightly taller diff ( 3.08 to 1 ) I might achieve this by installing a $ 150 diff rather than a $2000 5 speed gearbox.

I think the ideal would be a the JH 5 speeds diff at 3.55 to 1,  used with the 4 speed gear box would cut down the revs to 3000 rpm, still in the good tourqe range for the engine but not revving as hard. Problem is the 5 speed JH are not that common round here and classic cars are experiencing somewhat of a resurgence and not that many end up being wrecked to donate just a diff.  My spare diff in the picture is out of a Viva Magnum 1800, which has a slightly different hand brake arrangement but is essentially the same as on my 1974 JH.

The Torana Diff would be useful for those who end up with more horse power and torque from either a 2.2 l engine upgrade or a complete engine swap. The XU1 Torana had much success in the hands of the late Peter Brock on Mt Panorama and other circuit racing in Australia. With both the Torana and the JH using much of the components from the HB and HC Viva range it was always going to be a close but not a drop in replacement.

Could look at this a 5 speed box from a VK Commodore, very common and GM did not build any lemons did they?

Thanks for you interest. Tony H.

Attachment: commodore 5 speed box.jpg (Downloaded 90 times)

Last edited on 05-07-2007 11:52 am by Tony Hollart