Diff ratio help?

[muzz2005vzute]

Just wondering about diff ratios, what's the difference between 3:08:1 and 3:07:1? Is one of them for an auto gearbox or somthing? I want to put one in my manual v6 ute but just wanted to know the diffence

 

[Surfwagon]

For a VX-VZ the different ratio are from different size diffs with the same external size.
The 3.08 ratio is from the M78 which refers to a 7.8" crown wheel, M78 fitted to most V6 commodores.
The 3.07 is from the M80 which has a 8" crown wheel and the M80 is fitted to all V8's, supercharged V6 and some sports V6's.
Both 3.08 and 3.07 are usually fitted to auto's and some manuals.
For Manuals the best all around and easiest ratio to find is 3.45(M78) or 3.46 M80.
Both M78 and M80 are the same external size and are inter changable with one exception.
Some later VZ V6's were fitted with M80 diff that also had a larger 3 bolt doughnut flange fitted between the diff and tail shaft.

 

[muzz2005vzute]

So if I put a 3:07 diff in my ute and it had a m78 would that be bad for it?

 

[Surfwagon]

No not at all, basically 3.07 and 3.08 are the same ratio just different physical size crown wheel and pinions, the bigger the stronger usually.
Using either 3.07 or 3.08 ratio would make no difference to gearing at all just that the internals of the 3.07 M80 diff are larger hence stronger.
The different ratio numbers were designed so that it made it easy to differentiate between the smaller M78 V6 diff and the slightly bigger stronger M80 V8 diff.

 

[muzz2005vzute]

Alright so it will be alright in a v6 ute. That's good to know, thanks for the info mate was really helpful