Diff Centres

[Rusty_T]

 ;)

Hi guys,

Replacing the wheel bearings and oil seal in the diff on the ute. What should the ratio be. The ute centre has a ratio stamped on it 3.89. Is that good or not. The part # on the gear and pinion in the cattledog  is 7406081 doesn't match either part # on the the diff.

ideas

Rusty

[mcl1959]

3.89 is standard for all FE FC. A stockie in good order can easily run a 3.55 ratio and improve fuel economy on long runs. 3.55 ratios first appeared in the EH.

Ken

[TTV6FC]

While we're on the topic,are FE and FC sedan diff centres EXACTLY the same?Cheers Jamie.

[mcl1959]

Well no not entirely, a scan through the parts book shows a change in the pinion shaft half way through FE. The lock pin also appears to be changed as well. These two items were probably changed as an improvement or upgrade. I can't see anything else different. Possibly the case casting was upgraded which would not necessarily get a new part number.

Ken

[newman]

3.89 is standard for all FE FC. A stockie in good order can easily run a 3.55 ratio and improve fuel economy on long runs. 3.55 ratios first appeared in the EH.

Ken

Also worth mentioning if you swap to a later diff centre (3.55) it's a different rear universal  ;)

Mick 8)

[FCRB26]

Yes thats a good point mick.

worth the effort i run a 3.36 in my stock FE good cruiser all round.

can be a little trying on the clutch but i will replace the engine and clutch soon as its age and condition are unknown

[ardiesse]

For the EH and later diffs the rear uni joint is the same as the front.

Me too.  I run a 3.36 diff in my sedan.  Maybe a little slower off the mark.  I don't have to slip the clutch any more than with a 3.89, but it's a far more relaxed cruise at highway speeds with a 3.36.

Rob

[hsv-001]

 Due to the lower tyre profiles to maintain highway speed at realistic rev.s and true speedo calibration a necessary evil

[newman]

Due to the lower tyre profiles to maintain highway speed at realistic rev.s and true speedo calibration a necessary evil

This link is always handy when changing diff centres / tyres etc.

http://www.kabamus.com/garage/gears.html

Mick 8)

[MRJ68]

is the diff housing the same in the eh as the fe or do you cange the housing as well

[mcl1959]

Apart from a few subtle differences (bearings etc) the whole lot is an interchangeable unit. So diff centers can be interchanged.
However, for a better selection of wheel cylinder sizes to suit the front brakes it is better to use a HR rear end.
Then again if you are going SBC, maybe a Borg Warner or 9 inch would be better


Ken

[57effie]

Hey Ken,

I have been given an EJ. Very sad but it has a 149 that runs and some other bits I thought I'd scavenge. It has a Hydramatic in it. Is the diff ratio of the auto the same as the manual because I thought I might use it in Effie. What else might be worth scavenging ?

Cheers

Mark

[mcl1959]

Stock ej auto has the same diff as a manual, but have a look, it may have been changed....

Ken