Diff ratios

david muir · Post by **david muir** » Wed Oct 31, 2012 7:18 pm

What diff. ratio was the most commonly fitted , from new, in the 3.8 series?
I was led to believe that my 3.31 was but I hardly see this ratio mentioned on here.........is it unusual?

David

christopher storey · Post by **christopher storey** » Thu Nov 01, 2012 5:23 pm

No, 3.31 was standard for most if not all RHD road cars up to about 1964 when I think a few had 3.07 just before the 4.2 was introduced . However , virtually all N.American cars had 3.54

buchies · Post by **buchies** » Thu Nov 01, 2012 11:46 pm

Hi All,

What is the easiest way to determine what diff ration is in place on my car?

Thanks
Philip

christopher storey · Post by **christopher storey** » Fri Nov 02, 2012 11:47 am

Attached to one of the backplate bolts should be a tag with two numbers on it which represent the teeth on the crown wheel and pinion. Thus 3.07 is 43/14, 46/13( I think ) is 3.54 and 43/13 is 3.31. If the tag is missing then you will have to resort to counting revolutions of the propshaft against several revolutions of a roadwheel

graemea · Post by **graemea** » Sun Nov 04, 2012 5:41 pm

Hi

No need to get under the car.

Just look at your speedo and compare the numbers to this list:

http://www.e-type-online.de/xkeratio.htm

Regards

Graeme

buchies · Post by **buchies** » Tue Nov 06, 2012 1:02 pm

That's very useful thank you for that.

christopher storey · Post by **christopher storey** » Tue Nov 06, 2012 3:49 pm

Unfortunately, Graeme's advice presupposes that neither the speedo nor the axle ratio have ever been changed during the car's life. Whilst in New Zealand that may be the case, many cars found in Europe have a colourful history with many parts substituted .

buchies · Post by **buchies** » Wed Nov 07, 2012 10:24 am

christopher storey wrote:Unfortunately, Graeme's advice presupposes that neither the speedo nor the axle ratio have ever been changed during the car's life. Whilst in New Zealand that may be the case, many cars found in Europe have a colourful history with many parts substituted .

Hi Chris

You make a valid point. My car seems to be unmolested and I was keen to use this as yet another test to support my theory.

So far so good.

Regards,
Philip

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