Vlad's rides thread

[psyolent]

Is the M76 IRS diff whats in our Commodores? like VR onwards non live axle? or VT onwards. the VT onwards were 3.07...

[vlad01]

Im not sure. M78 comes to mind for VT onward, VQ-VS IRS I would imagine to be M76

[immortality]

VN-VS live axle is commonly referred to as M78, VP to VS IRS seems to be the M76. With the VT model the V8 and L67 got the larger M80 diffs but the standard V6 models continued on with the M76.

The interesting thing is that all the VL-VS era diffs I've stripped, both live axle and IRS have all had 0575 BW/BTR gear sets fitted.

Anything 3.08 or 3.45 would be M75/M76/M78, diffs with 3.07 or 3.46 will be M80.

[VK_3800]

^ Rumours from school holiday forum posters as you've discovered. Ask someone on the Just Commodores forum what the different between the M75 and M78 is and they will tell you its the four spider centre and 28 spline axles; its not, these designations refer to the gears.

The Commodore and related vehicles got a bit of everything (there are some oddballs) but for the most part all VK 1/2 to VT S1 (both live axle and IRS) are M75. From there the V8s are generally M80 and sixes still M75 right up to VZ.

There are a couple of VR/VS listed as M78 including 3.27:1 ratio so I'm guessing those are the HSV Hydratrak.

Some of the later live axle one tonners and Crewman are M78 and M86. AWD models had an M70 front axle.

Can't see any M76 listed at all, possibly another rumour generated due to the change in pinion yoke on the M75.

The ratios as mentioned are a good way of distinguishing M75 from M80 (3.08 vs 3.07), assuming you're being told the right info.

[immortality]

It is stupid isn't it. All the car manuals I have (like Gregories) refer to them as M78 and that is possibly where the misnomer started? They do refer correctly to the Vk1/2 as having the M75 though......

As far as I know the only M78's fitted to Commodores were the HSV Hydratrak units, a mate recently had a diff built using parts from a hydratrak unit and the housing had to be modified for the larger pinion bearing.

My theory on the M76 name is it's another misnomer to distinguish the IRS center from it's live axle cousins.

[vlad01]

yes it refers to the gears and they are slightly different. M78 being a little bit bigger OD but same ID on the crown and the pinion depth is different to accommodate.

From my diff builder the M78 is common in the fords where M75 was predominately a Holden thing for the live axles.

[psyolent]

good information to know, given i'll be ordering a spool in due course ....

[VK_3800]

From my diff builder the M78 is common in the fords...

The later ones (depending on how old you are I guess!), changed over somewhere around EF I believe but no Ford expert. Earlier are still M75.

[vlad01]

From my diff builder the M78 is common in the fords...

The later ones (depending on how old you are I guess!), changed over somewhere around EF I believe but no Ford expert. Earlier are still M75.

yes EL or EF is what I think as awell. Ford still run live axle, well they did

[HQ355]

good information to know, given i'll be ordering a spool in due course ....

Put your uv and radiation suit on and do a cig locker !