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Rear end gear ratios  Rate Topic 
 Posted: 07-03-2016 04:12 am
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Joined: 10-09-2014
Location: Paso Robles , California USA
Posts: 2
I have a JH5 built Dec 1974. Discovered today while going through the rear end it has a 11 tooth pinion / 41 tooth ring 3:73. Thought it was supposed to be a 3:45 with the 5spd. Maybe it was changed sometime in the past but no record of that being done. Have detailed records since new. Anyone else had this experience? Anybody have a 3:45 rear end they want to sell or trade??????

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 Posted: 07-03-2016 07:35 am
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Joined: 07-16-2014
Posts: 188
Hi Jetcat

What's the chassis number of your J-H? According to Richard Calver, J-H's with chassis numbers between approximately 18300 and 18900 had the federal rubber bumpers (making them look like J-H5s) but the 4-speed drive train. Is it possible your J-H is one of these vehicles, and a PO upgraded the gearbox to the Getrag at some later stage? It may even be possible that your J-H was built in its current configuration, checking the build sheet (which you can get from Martin Robey here in the UK) would confirm.

I don't know about the States, but here in the UK where thousands of Vauxhall Magnum 2300s (as well as a few hundred J-H5s and GTs) fitted with the 3.45:1 cwp axle were sold, this axle is now extremely rare. I managed to find a spare one for my GT from a Vauxhall racer, which is now being fitted with an LSD. In the States you may struggle to find one unless someone is breaking a J-H5 or GT.

You may be better off keeping your 3.73:1 cwp axle and swapping out the now very rare Getrag for the easy to find Toyota W58 gearbox, which is a common conversion giving a proper overdrive 5th gear.

Apparently with a stock 907 engine the W58 is a good match for the 3.73:1 cwp axle.

Hope this helps.

Best wishes,

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