What rear end is this?

R

Rollin

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Joined
Jun 19, 2012
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4
Location
Brisbane, Queensland, Australia
Hi there! I've been looking though this forum for information and I'm really hoping you guys can help me.

I'm from Australia and I've been googling my fingers off trying to find some information on differentials in American cars, and I think after finding this forum I might be in luck...

Years ago I bought a second hand diff for my car, a 1994 ED Falcon, which had a locker center already fitted to it. This locker is my most loved component in the entire vehicle. Like, I fricken LOVE it.

I recently bought a second Falcon and I want another locker for it, so I have to figure out what American cars used the same diff I have so I can get a matching locker.

After much searching I think it might be a richmond or powertrax no-slip, but I can't find any pictures which look the same as the center I have, and there is nothing listed in the catalogue for my car of course.

Looking at this thread:

http://www.vettemod.com/forum/showthread.php?t=4460

It seems the housings and center are very similar to what is fitted to 1990's model Ford Falcons and Holden Commodores, and also late 80's model Australian versions of the R31 Nissan Skyline.

In Australia we call them "Borg Warner 78s" and all live axle Falcons and Commodores from about 1988-1989 though to 2000 have either a 4 pinion open or 4 pinion cone-type limited slip center in them (Which I think is what you guys call a 'posi'?), with 28 spline axles. I think this center might be what you guys call a '9 bolt' or a '10 bolt'?

Falcon diffs look like this:

Back of housing with rear cover removed

diffmarkedup.jpg

'Open' type 4 pinion center:

falcondiagtool004.jpg


falcondiagtool003.jpg


And the rear covers (Falcons use a watts link rear end, hence the alloy rear cover with the pin)

AU-EBrearcovers.jpg

We can get 'lokkas' over here which look like this:

91028000_L.jpg

But they're shocking. Very loud and occasionally they single wheel :/

The one in my first Falcon uses the factory side gears and looks like the top 3 components in this pic:

Lockrightbits1.jpg

Can anyone shed some light on this? Is there a currently available richmond/powertrax center that uses the factory side gears at all?
 
That's a Borg Warner 9 bolt, australian axle. It's indeed also called a 78. I have 5 of those things for my F bodies. It's indeed similar to the stuff in the skyline.

You can get a posi setup for those, a lot of F cars came with cone type posies for those. The lockers are a nightmare, I will not run them.

Here's part of a pictorial I did for some F body guys on redoing the worn cone type LSD on the cheap:

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Shit, if only i had known about the watts linkage on the falcons, I could have gone with a normal watts instead of a reverse. Are those lids cast aluminum?

I see a wee bit of difference with the f body axles, the lower 9th bolt on yours is larger than the rest and the upper dowel is not there on the f cars. Must be because of the watts linkage on the lid so it's positively located?

9 bolt F car axle:

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Thanks for the replies!

pancake - yes, this one definitely came in a ford. There are versions with different axles and axle tubes etc to suit Holden (GM) and Nissans though. I'm lead to believe that Borg Warner developed a 'generic' rear axle setup that could be easily adapted to suit different vehicles (hence it's use on many different Aussie vehicles). My challenge is to find this axle in an American car so I can figure out what the locker part number is!

The picture in the mustang thread is exactly what is under the back of my car, and it is quite freaky to read about it on an American forum lol. Maybe I could make my millions selling Falcon watts link rear covers to the mustang guys? :)

I doubt it would be a ford 8.8 derivative, as the crownwheel is only about 7.8 inches in diameter (hence, BW78 designation). Earlier versions available here were BW75 (7.5" crownwheel).

Twin Turbo - I've seen your build thread and your fabrication skills, I absolutely love your work!

The rear covers are cast aluminium, and depending on year model the mount is in a slightly different place, as earlier Falcons were known for their 'roll-oversteer' tendencies when pushed hard through corners. In the pic I posted of the rear covers the one on the left side is from AU Falcon (MY98-2000) and the right side is EB (MY1991-1993). As you can see the rear cover mount is noticably lower on the later model.

The dowels at top and bottom are to locate and support the rear cover, the larger bolt hole at the bottom is because the lowest bolt also functions as a drain plug.

Which lockers have you had dealings with? The one that replaces the side gears is an absolute shocker, but the one that retains the factory gears is (for me) prefect for the job - I'm what you would call a more.... 'severe duty' user I think...

Is it still possible to buy the lockers I want? Looking in the Powertrax Application Catalogue (http://www.richmondgear.com/01pdfs/PTRAXAPP.pdf) it seems I have two options:

Camaro 1990-2001 GM 7.625" Ring gear 28 spline/10 bolt cover P/N 92-0776-2805

or

Fairmont 1978-1983 Ford 7.5" Ring gear 28 spline/10 bolt cover P/N 92-0675-2805

Can't tell if this is a 4 pinion locker or if it uses stock side gears...any ideas?
 
I was surprised to learn that GM put the Borg Warner 9 bolt in some 3rd Gen f bodies. I always thought they all got the 10 bolt.. so cool.. learned something new.

There seemed to be a whole lot of posts about this rear end on thirdGen.org that say it is stronger than the 10 bolt and impossible to find parts for. So that doesn't help!
 
Quite a lot got them, most of the J65 brake optioned 86-89 TAs and 86-90 Z28 or IROCs got them. Like I said, 4 of my cars here have one.

It's not impossible to find parts, the cones are readily available, the bearings and all too. Not an issue.
 
The cones they sell will need machining or the housing needs machining if you use an f car posi.
 
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