Identifying diff M78 or m80 in VX V6

[Bawwx]

You convert the M80 to fit the tailshaft, you don't change anything on the tailshaft. You undo the big nut in the 4 bolt flange and bolt the 3 bolt one from your old diff in. Others will chime in about if this will effect the backlash or the preload.

Do you know what model this diff came from?

the M80 came from a VY SS, it seems a little bit more complicated than just swapping the bolts out. My old diff is the M78 so don’t exactly have the”old” 3 bolt.

 

[_R_J_K_]

My old diff is the M78 so don’t exactly have the”old” 3 bolt.

You bolt the M78 flange onto the M80. Or get another tailshaft with the flange to match like EYY said.

You got pictures? Maybe it will be easier to explain that way.

 

[_R_J_K_]

Have a read of this too, you will need to mark the nut if you take it off - Changing flange on LSD, from 3 bolt to 4 bolt | Just Commodores

 

[_R_J_K_]

the M80 came from a VY SS

Re-reading this thread, you shouldn't have to change anything. All the VXs and VYs used the 3 bolt diff flanges with the rubber donuts, and there is no 4 bolt donut so I'm not sure what you're seeing.

 

[Bawwx]

Is the M78 in a VX V6 28 spline or 31 spline? Decided to just get the M78 TruTrac instead of messing around with converting the M80.

 

[Immortality]

Factory diffs are 28 spline.

 

[Bawwx]

So i just inquired about the Harrop Truetrac M78 28 spline LSD and the bloke said it has to be a live axle, where as the VX is IRS. Do Harrop Truetracs still fit with the IRS?

 

[Immortality]

The IRS centre has an extra groove inside the spline to retain the output shaft hub. IF the groove isn't there than it won't work properly as the hub can float in and out.

 

[Bawwx]

Thanks for the reply. So what is the best brand option for an M78 LSD centre with IRS?

 

[_R_J_K_]

So i just inquired about the Harrop Truetrac M78 28 spline LSD and the bloke said it has to be a live axle, where as the VX is IRS. Do Harrop Truetracs still fit with the IRS?

Did you ask Harrop?

Seriously though, just get under the car and look at what flange you have, then just look for an M80 with the same flange.