Borg Warner Diff

[Grah]

Gentlemen,

I am doing some works on my FC Ute, affectionatly known as Doris, pictures posted herein. Engine is now apart and YT head away for hardened exhaust v/v seats. I took the cover off from the diff today and to my surprise found black burnt smelling oil. The diff is a Borg Warner 78DA-4005-HA with a ratio of 2.92 : 1. I am presuming it must have some kind of limited slip mechanism utilising clutch plates which has at some time burnt the oil. Would this be correct? Are parts for these diffs readally available and how much power will they safely transmit?? Could someone recommend a suitable replacement oil for this diff type? Finaly is there anywhere I can get any information on the where this diff has come from?? The net brings up a blank, loads of info about 9" Ford diffs, but little on the BG. A source has advised that it might be from a Valient?
Look forward to any information you can supply.
Best regards,

GCP. Tasmania.

[4hammers]

G'day Graham,
The Borg-Warner was a diff used in Volvos as well. I did a lot of reseaarch on these when looking at putting a hotter motor into an FB ute I was going (Still might when I am 50) to build. The 2.92 in definately a Volvo ratio.
Is it a disc brake reaar end? The reason I ask, is these diffs are relatively easy to drop straight in. Only an inch marrower & minimal mounting modifications apply. If it is a disc rear end, it will also have little drum brake set ups inside the disc hub, that are for the handbrake.

The diffs are bloody strong. V6 easy, V8's cool, unless very tough motor.

I will ask  Simon next time I see him & get him to put me in contact with Byron. I was told it was a 9", but if it has BW, then it is.

Parts are available & the best oils are also readily available from any auto store.

Are you still up North?

Rob J

[Grah]

Rob,

Thanks for your swift response.
Not up north, a lot of water has gone under the brige since we last met. Now live down in Kettering, bailed from Hobart, son at Uni etc.
Still rattling around the world like a luni. Only been back 2 weeks and probably off again.

Diff and back end are drum brakes, from end is HR with Torana discs.

Like I said the oil was very black so I reckon the clutch plates have been slipping or maybe that what they are designed to do?

Is there a tuning guru for 6's in Tassie, need to speak to someone about how far I go???

Graham.

[Dr_Terry]

Hi Guys.

The diff you have is a 78 series Borg Warner, & from the part number is probably out of an early XD Falcon.

While the later 4-pinion 28 spline B-W diffs as used in late Falcons & Commodores are very strong, the same cannot be said about these earlier efforts. Many of these diffs are only 25 spline 2-pinion.

A 9" conversion is probably over kill, & since you already have the housing in the car, why not convert it to a later stronger version with whatever ratio is more suitable (2.92 is very tall & usually seen in large motored cars with automatics).

On the subject of Volvo diffs. To my knowledge Borg Warners were not used in Volvos, they used the Dana 44, fairly strong & reliable, but because Volvos were usually 4 bangers or small 6s the ratios are usually around 4.0:1.

Dr Terry.

[Grah]

Thanks for your response Dr Terry,
This car runs a modified Holden 6, through a Celica  steel case  5 speed box, what ratio would you recommed? Get up and go has always been slowish, obviously due to the fitted ratio, but crusing is very good, low RPM and good fuel economy.
do you know if any books have been written about tuning a Holden 6 or is done by experience?
Grah.

[4hammers]

Hi Guys.
Yes, Dr. Terry. Now that you mention it, I have made a boo boo.
It was the Dana, NOT the Borg Warner used in the Volvos (Been a couple of years since I looked into them & got mixed up. There are some posts I put up ages ago, where I get it right). They were the same diffs used in the Jeeps, etc. But I know there were more ratios than that. I was planning on taking one out of a 164 (I think that was the model) Wagon. These were different to most of the other ratios. Not sure why, but I assume it was a "Touring Wagon" ratio. The wagon was an auto. I found out about it from an very early "Street Rodder" magazine article.

Sorry for the mis-info Graham.

Rob J