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old yukon 08-25-2012 09:36 AM

is this a borg warner 76 or not?
Hi Guys
Im having trouble getting a rebuild kit for my rear differential.

its a GU4 rear axle ( 3.08) with IRS, from a 1999 lumina 3.8L AT

here is a similar diff, not mine

thanks in advance to anyone who can help id this diff, so that I can order a reuild kit !

big gear head 08-25-2012 09:48 AM

That's a new one on me. I've never seen a Lumina with a rear differential. Did you try Randy's Ring & Pinion, DTS, National Drivetrain?

old yukon 08-25-2012 11:50 AM

Tried them all no go !

I did 101 searches and the best I cam up with was a Borg warner M78

But every image for a borg warner 78 doesn't match to a Chevrolet Lumina 99.

this is not mine but it come up as a 3.08 Irs m78

this has me stumped.

old yukon 08-25-2012 11:59 AM

Correction borg warner 78 not 76 as the title of the thread says.

Big gear head, you posted something on the borg warner 78 being from Australian rear ends, what would it be doing in a 99 Chevrolet Lumina ?

lmsport 08-25-2012 01:21 PM

GM shares some platforms with Holden, their Australian operations. The GTO was a Holden chassis, as is the new SS. Rear drive and AWD is a staple in the Holden lineup.
Is this in a Lumina van? Which engine does it have?

old yukon 08-25-2012 01:25 PM

Thanks for the reply lmsport

no its a sedan

the id tag says engine- LN3 but it looks a lot like the the 3800 series ( L36)

big gear head 08-25-2012 04:06 PM

Drivetrain - Forums
Go here and see if you can find some information. There are a few guys on there that order Borg Warner parts directly from Australia. That is definately a Borg Warner differential that you have. The '04 to '06 GTO, some 3rd gen Camaros and Trans AMs from '85 to '90 and the G8 all used the Borg Warner differentials.

old yukon 08-25-2012 09:40 PM

You dont call yourself Big Gear Head for nothing. Fount it, i think.

GM 7.75 IRS Rear - 04-06 GTO

its a GM 7.75 IRS Rear - 04-06 GTO


big gear head 08-25-2012 11:03 PM

I rebuilt one of those about a year ago. Randy's had the kit, but it was expensive. They have a reputation for causing problems around 20,000 miles. As I understand it they are actually built by Dana now. Dana suposedly bought Borg Warner in Australia and does the GM differentials there now. They used Koyo bearings in them and they didn't hold up very well. I've still got the GM alignment tool for lining up the GTO rear sub frame when reinstalling the rear end.

old yukon 08-26-2012 12:15 AM

Man now your opening up a new can or worms.

But is seems an important one.
sub frame alignment

GTO Alignment Process - Forums

official procedure

here a version of the tool by Pedders

thanks again, your the man !

Hay, anything else I must know before going ahead with the rebuild??

old yukon 08-26-2012 12:36 AM

hears the front tool while we're at it...

Might as well do the who suspension job with all that effort.

old yukon 08-26-2012 11:54 AM

you said you have the Gm tool, right
could you give me the measurements star to star so i can fab up my own jig

that will be a great help

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