M80 diff, Changing Diff Flange, 3 Bolt to 4 Bolt

[Immortality]

This has been asked a few times so I thought I'd create a dedicated thread to the subject as I was just asked again.

Hey mate I see you know your stuff about diffs. Still can't find a thread on info I need. Am putting a m80 with a trutrac in my vs statesman but need to change the flange from 3 bolt to 4 bolt. Is there a process do I count the turns when taking bolt off and back on. Mark it with paint etc any info much appreciated as I'm paying $1500 for the diff

In a Nut shell yes. Measure and mark with a paint pen where the nut is on the pinion. Remove the nut, pull off the 3 bolt flange (will need a puller to do this). Cut off the unthreaded end off the pinion (it supports the drive shaft when using the rubber doughnut type coupling) then fit the 4 bolt pinion flange and do up the nut again making sure not to over-tighten the nut and create extra pre-load on the pinion bearings. (A touch more pre-load probably won't hurt if it's got plenty of miles on it).

Fairly sure a few members on here have done the conversion so may be able to chime in with any extra tips on doing this job.

 

[Immortality]

Reserved

 

[Havabigjuan]

Looks like you know your diffs....please, some info would be appreciated

I am wondering if you know anything about Adventra diff into VY v6?

I am chasing a 3.46:1 and can find Adventra diffs easy, but not standard m78 or m80....

 

[Immortality]

Not really unfortunately.

@Fu Manchu is probably a better person to ask, he should see this notification.

 

[Fu Manchu]

Adventra are just a regular open diff. No fancy stuff in them.

 

[Havabigjuan]

Adventra are just a regular open diff. No fancy stuff in them.

correct, but what do I have to change on one to fit to a VY v6?

I assume the yoke or similar where it attaches to driveshaft??

 

[Lex]

correct, but what do I have to change on one to fit to a VY v6?

I assume the yoke or similar where it attaches to driveshaft??

Try a vx - vz manual v8 diff.
They have that ratio 3.46.

I have a m80 that was built for me with the 4 bolt flange & is LSD.

I tried changing the flanges myself & stuffed up.
So, ordered what l wanted (3.46 with the 4 bolt flange).

 

[Immortality]

Problem is, if you change the diff ratio in the rear you also have to fit the matching ratio in the front diff

 

[Lex]

Problem is, if you change the diff ratio in the rear you also have to fit the matching ratio in the front diff

He was asking about an Adventura diff into a vy v6.

He doesn't have an Adventura.

 

[Immortality]

Oops...