The differential thread

[TUFGMHParticipant SydneyVH SL/E & VK Calais LS1 View build HERE Member since: March 2, 2015 Posts: 96]

With a fresh forum comes the need for a good arsenal of info, so here goes….

This thread will be for explaining the in’s and out’s of Commodore diffs. More info to be added, but the plan is to make this initial thread the comprehensive guide.

Diffs from VB on, smallest to largest..

-Small Salisbury “8 bolt” solid axle. These were standard fitment for VB-mid VK sedans and wagons 4.2L (253) and smaller. Details were: 25 spline axles, drum brakes on all except later SL/E and VK Calais. Round rear diff cover with a steel Hex plug. A universal joint style yoke. Ratio listed on yoke collar (2.78,3.08,3.36,3.55,3.91). 253 and EFI 202 models were fitted with the larger V8 yoke found on a 10 bolt.

-Large Salisbury “10 bolt” solid axle. These were standard fitment to all 5L Commodores VB-VK and optional for 253. LSD was offered standard only on manual 308’s and HDT builds. All were disc brake. 10 bolts had an oval backing plate, and were factory fitted with 2.60,3.08 gears.

-Introduction of the M78 Borg Warner. During the later part of the VK series, 6cylinder Commodores were fitted with the Borg Warner differential. This come with a host of small changes. The universal yoke was replaced with a flange. All VK Borg Warners were fitted with 3.23 gears and 25 spline axles. They were the same width as the previous Salisbury’s.  The rear cover was similar to the small salisbury but had a rubber fill plug. It is said that the VK version had same size axles, and on viewing the housing personally, it appeared so, but is yet to be confirmed for this thread.

During the VL series, a few revisions were made to the Borg Warner. All VL diffs were 11mm wider (approx 131cm from disc backing plate to disc backing plate). The 10 bolt was replaced with a 28 spline M78 with 4 pinion centre, this saw use behind 5L and Rb30ET engines, and the easiest way to identify are the numbers “950” & “951” stamped on the outer axle ends. Discs were standard on all 28 spline and Calais models, and optional on lower trim specs. Common ratios were 3:08 & 3.45 in Aus models, the NZ 2L export saw 3.91’s. At the end of the VL series, the 25 spline, 2pinion M78 ceased as an option in the Commodore range. 28 spline M78’s become standard fitment til the end of the VS.

During the VN-VS series, the solid diff widened another 41mm and rear discs becam standard fitment. The VN GroupA and SV5000 were the only exception to this, and were fitted with VL width diffs to allow their respective wheels to clear. IRS first saw use in the VQ Statesman & Caprice, and saw use in the VP-VS range after revisions, before becoming standard fare from VT onwards. All utes and wagons continued with a solid axle til the end of VS. No real other changes were seen outside the inclusion of ABS which required sensor and sensor rings. On IRS, the sensor rings were mounted to the stub axles, on a solid axle they were mounted to the outer axle. The Hydratrak centre was introduced in the VR/VS HSV. This was a viscous coupling which replaced the clutch setup in an LSD centre. 3.7:1 became available at this time as well. BW 78 centres were also found in other Makes such as Ford and Nissan. Ratio’s available from models such as the Pintara are a popular fitment to Commodores, being 3.9 & 4.11.

When the VT was released, M80’s were introduced in the 5L and Super 6. M80 stood for the upgrade from a 7.8inch crownwheel to an 8.0inch.

To Be Continued

[VRSenator065Participant Adelaide SAVR Senator LSx454 1960 Kombi (project) 1921 Nash Hot Rod (future project) View build HERE Member since: February 17, 2015 Posts: 5 777]

So once you start making too much for an M80 in an IRS Commie the choices become a little more expensive.

Pretty much it comes down to some sort of fabricated Ford 9″ conversiion like the G Force, and the numbers start pushing $10k.

The Aussie alternative is a Harrop 12 bolt, bolt, which is essentially a remanucatured Chev 12 Bolt. For the record the crown wheel is 8.9″ so I guess it could be called an M89 These are around the $5k mark.

Either are a good option, imo what the Harrop has going for it is this;

1. Its a direct bolt in replacement for an IRS VR
2. Its an Australian product sold locally
3. Its not Ford
4. Harrop, although expensive, are recognized as top quality
5. Its available in a full range of ratios
6. The help, advice and service I have received by Mark at Harrop has been excellent.
7. They are available in a range of ls options, locker, tru trac etc.

To give an idea, this is the 12 bolt and M78 side by side

• This reply was modified 9 years, 1 month ago by  VRSenator065.
• This reply was modified 9 years, 1 month ago by  VRSenator065.

[OLD GMHParticipant PerthVB Commodore View build HERE Member since: March 2, 2015 Posts: 29]

What’s the go for early girls when you don’t want to go 9 inch? Have heard the VL Turbo diffs are the ones people usually choose. What kind of power do they hold up to?

[cava454Moderator 93 VR BT1 View build HERE Member since: February 20, 2015 Posts: 2 390]

OLD GMH wrote:

What’s the go for early girls when you don’t want to go 9 inch? Have heard the VL Turbo diffs are the ones people usually choose. What kind of power do they hold up to?

a lot of the VN boys use them as they have a shorter track and directly bolt it. Makes for wider wheels and more dish.

As for being strong they are exactly the same as the VN v8 diffs being 28 spline.

 

Also m80 diffs came in from VT series 2 onwards. So I think that makes it only the ls1 v8’s not the 5.0

• This reply was modified 9 years, 1 month ago by  cava454.

[TUFGMHParticipant SydneyVH SL/E & VK Calais LS1 View build HERE Member since: March 2, 2015 Posts: 96]

OLD GMH wrote:

What’s the go for early girls when you don’t want to go 9 inch? Have heard the VL Turbo diffs are the ones people usually choose. What kind of power do they hold up to?

A 9 inch can easily be done but people want twice the money, the centre in a 9 inch nearly weighs as much as a “VLT” diff, and the weak point can end up being created by converting a 9inch. Personally, most of my friends have had axles fail over centres, none have had billets fitted. Another problem many have with a nine inch is tailshaft clearance as most have the pinion offset to one side and most want to run a thick single piece tailshaft which requires chopping of body bracing to clear.
People have run 9’s with RB30ET’s on slicks/transbrake and survived a while. Another upgrade to consider is a XR6T ute diff with a bigger centre.

[daveParticipant daveVK, L98, tremec tko600 View build HERE Member since: March 6, 2015 Posts: 46]

Hi. Anybody got an opinion of how much power the VL turbo, VN V8 lsd borgwarner diff will handle? Have one in my VK with 31 spline axles. Just wondering if I will break it easily.

[VRSenator065Participant Adelaide SAVR Senator LSx454 1960 Kombi (project) 1921 Nash Hot Rod (future project) View build HERE Member since: February 17, 2015 Posts: 5 777]

That’s going to be a really a hard question to answer. Depends so much on how you treat it, and what your are doing with it.

[MANTA 185iParticipant KiamaVS HSV Manta 185i. A 600hp 383ci weapon wrapped in a stock shell. View build HERE Member since: March 2, 2015 Posts: 11]

Great write up TufGMH. Looking forward to reading more.

 

Cheers.

[cava454Moderator 93 VR BT1 View build HERE Member since: February 20, 2015 Posts: 2 390]

dave wrote:

Hi. Anybody got an opinion of how much power the VL turbo, VN V8 lsd borgwarner diff will handle? Have one in my VK with 31 spline axles. Just wondering if I will break it easily.

 

pretty sure ls1 pwr went 8’s with same diff.

[Phire aka GmfanParticipant VictoriaVT LS1 Wagon View build HERE Member since: March 3, 2015 Posts: 105]

Unfortunately vlt diff’s are starting to fetch higher dollars. There are vlt diff’s on ebay no axles for over $1000. How much does it cost to narrow a diff? I picked up a complete diff with discs and calipers $100 from a vs. Seen some around on ebay for $80-$100.

[VRSenator065Participant Adelaide SAVR Senator LSx454 1960 Kombi (project) 1921 Nash Hot Rod (future project) View build HERE Member since: February 17, 2015 Posts: 5 777]

My view is what diffs can take is a little like transmissions. Some guys will run a 9, others kill them in the first burn out. Depends on your mechanical sympathy, what exactly you are doing with them and I think a little dose of luck

[cava454Moderator 93 VR BT1 View build HERE Member since: February 20, 2015 Posts: 2 390]

Phire aka Gmfan wrote:

Unfortunately vlt diff’s are starting to fetch higher dollars. There are vlt diff’s on ebay no axles for over $1000. How much does it cost to narrow a diff? I picked up a complete diff with discs and calipers $100 from a vs. Seen some around on ebay for $80-$100.

im about to venture down the diff shortening path. It’s about $1500 more if u require tub work.

[VRSenator065Participant Adelaide SAVR Senator LSx454 1960 Kombi (project) 1921 Nash Hot Rod (future project) View build HERE Member since: February 17, 2015 Posts: 5 777]

But would you spend that sort of cash on an M80? Maybe a better bet to build a 9″ for a live axle that in the end will be so much stronger and much more sellable if you ever want to?

[cava454Moderator 93 VR BT1 View build HERE Member since: February 20, 2015 Posts: 2 390]

I’m not talking m80

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