FE-FC Holden Discussion Forum

Driving from Melbourne to Perth across the Nullabor in an FC Ute, what would the best diff ratio be to keep the engine revs down but still be drivable around Perth.

And how do you tell what diff ratio you have already?

Kevin

On the housing of the diff it is stamped what ratio it is. may need a clean. I know because I just gave mine a clean ;D
For the ratio .. someone more knowledgeable than I can explain that!
Nick

You could get away with a 3.36 behind a grey and slip the clutch a bit on take off around Perth. This would save a fair bit of money on the trip. Normally I don't reccommend lower than a 3.55 diff behind a grey unless it has been given a bit of extra oomph.
A stock grey box has no external markings for the ratio, but red motor diffs have the ratio stamed on a circular metal disc surrounding the pinion shaft.

Ken

What was the mist common ratio or did it depend on the ratio. Out here they are all tall normally due to the flat remote area

Many thanks Ken.

Has anyone got a 3.36 diff for sale?   ;D

Kevin

I don't know about the most common - it depends on the car - Most 6 cyl manuals had 3.55 and most 6 cyl autos had 3.36 diffs whilst most V8 manuals had 3.36 and V8 autos had 3.08

Ken

ALL greys had a 3.89 as standard, end of story.
Most common replacement is 3.55, as it provides a slightly lower rpm at a given road speed, or higher road speed at a given rpm.
(sorry if this is too basic).
For a wide open road, 3.36 is popular, but, as Ken says, can be a bit of a burden off the line.
I'm sure I have seen many posts on the forum on how to calculate the ratio, but every 3.36 or 3.55 I have seen has it stamped on the external disc on the pinion shaft between the diff housing and the universal joint.
If the diff is out of the housing, you can see the ratio stamped on the crown wheel.
I'm away from home at the moment, but when I get back I will post a pictorial instruction for the archives (if not there already)
Cheers,
Gaz

I got a 3.55 diff,  ;D  I'll be putting that in for the drive to Perth. 

Can it bolt straight in or do I have to change anything??

Kevin

You will have to change the rear uni to a red motor uni.
Regards
Alex

G'day Kevin

I have driven my FE Ute accross the padock twice and have had no problems sitting on the speed limit.
I took a photo of my diff to see what the number was. It seems to have a plate over the original number.


(http://img.photobucket.com/albums/v162/58feute/Ute%20Stuff/UTEDITT008.jpg)

Anyhow it was in the ute when I aquired her at 54,000miles and I have not changed the oil yet...now 87,000

Fuel is relativly expensive on the Nullabour...but that adds to the experience of the crossing

These are the fuel prices on the 31 Dec 2011...Just sit back and enjoy the ride

Ceduna $1.56
Nullabor roadhouse $1.97
Madura $1.76
Belladonia $1.90
Norseman $1.56


Cheers
Gary

Thanks Alex.

Thanks Gary, that's interesting to know.  I calculated (for a rough budget) fuel at $2.00 per litre so anything under that will be a bonus.

Kevin

http://akb.norbie.net/Public/Gearing.aspx

diff      rpm @100 kph
3.888= 3400
3.700= 3240
3.550= 3100
3.360= 2940

diff      rpm @80 kph
3.888= 2720
3.700= 2590
3.550= 2490
3.360= 2350