Identifying diff M78 or m80 in VX V6

[Bawwx]

I was just wondering how can I tell whether the diff in my VX series 1 V6 commodore auto is a m78 or m80 as I’m getting an Eaton TruTrac and need to know which one to get. In another forum post detailing diffs, it isn’t specified whether the VX V6 continued with the m78 like the VT series 2.

from late model VK's everything up to VS was BW78. VT s2 V8 and super6 models got the BW80, standard V6 models continued with the BW78

 

[Immortality]

Is there a tag (white sticker) on the side of the diff, should a couple of letters on it and possibly the diff ratio.

 

[Bawwx]

Thanks for the quick reply!
it does have a white sticker with the said letters, although can’t get underneath to have a look at the moment. How would this identify whether or not it’s an M78 or m80? As I’m planning on keeping the 3.08 (which I already know that it’s running) gears to put in the TruTrac for now.

 

[Immortality]

3.08 is a M78 centre

 

[_R_J_K_]

In another forum post detailing diffs, it isn’t specified whether the VX V6 continued with the m78 like the VT series 2.

Every N/A V6 up until the VZ had the same M78 (supercharged were M80). AFAIK Eaton still don't make a Truetrac for the M78, only Harrop do and it costs a motza (although there are the Torqueline alternatives). You'd be far better off finding a cheap VT-VZ M80 diff housing and using that with the Truetrac as the M80 housing will bolt straight in (minus swapping the input flange in some cases) and be way cheaper.

 

[vr304]

Thanks for the quick reply!
it does have a white sticker with the said letters, although can’t get underneath to have a look at the moment. How would this identify whether or not it’s an M78 or m80? As I’m planning on keeping the 3.08 (which I already know that it’s running) gears to put in the TruTrac for now.

Just curious as to why your keeping the sluggish 3.08 gears? If your doing a true Trac now would be the perfect time to put a decent ratio in

 

[Immortality]

Is this for a skid car?

If so I would say forget the truetrac and go straight to a minispool along with a gear change. The V6 doesn't have enough grunt to get good wheel speed with a 3.08 ratio diff. Something like 4.11's will solve that issue.

 

[Bawwx]

Thank You Immorality and _R_J_K_ for the replies! Hope Your all having a good Christmas!

Is this for a skid car?

If so I would say forget the truetrac and go straight to a minispool along with a gear change. The V6 doesn't have enough grunt to get good wheel speed with a 3.08 ratio diff. Something like 4.11's will solve that issue.

that was going to be my next question. I understand the lack of power in the V6 models, and a gear change would be a great option! I was going to ask what alternatives I have with changing the diff as yes indeed It’s going to be a skid car although the issue with that is it’s also my daily (I know not the best choice at all to have a skid car as my daily!)
And a common and most ideal thing to do is just use the money I would spend on upgrading an Auto Berlina and just buy a V8. Regardless of what I’m told I’m almost definitively going to eventually rebuild the whole car and spend the money on it.
The problem I came across with a full spool or mini spool or even welding the M78 is that it’s a daily.
as for the keeping the 3.08 gear ratio, I would prefer a higher ratio but that also comes at a cost above the already $1k+ for the Harrop TruTrac, so gears would have to come later and I’m thinking a new diff is starting to become more needed and not wanted over time.

 

[Immortality]

Upgrading to the M80 would be most effective cost wise in your situation as the parts are cheaper all round.

Go find a cheap Auto V8 VT/VX/VY m80 diff from the wreckers and rebuilt that to suit.

 

[Bawwx]

Is there much work involved in converting an M78 to M80? Regarding tail shaft, Auto trans, gear ratio etc?