HR diff centre conversion

[newman]

Hi all,

I've decided to go with a 3.55 HR diff centre into my EJ,this with the 14" rims will give me lower revs at highway speeds. I found a few postings on how to do this so I got a centre had it all checked out, fitted a new pinion seal to be safe and I'm ready to go.
Wrong, I just need a point cleared up for me as you guys have probably done this numerous times. On the previous postings I've read they say to change the rear universal and U bolts over to red motor ones e.g HR etc. Does this apply to EJ's as well as the pinion looks the same as the 3.55 I want to update to ?
I do know this is the FE/FC site but I thought I'd have more chance of a response here as it's Grey motor related and was hoping there might be some EJ drivers amongst your ranks.

P.S. I'm still looking for an FC so I won't feel out of place here.

Mick

[FC427]

Mick the rear on your EJ  uni should be the same as EH HD HR ....Did you check to see what ratio was in your car before you change it  it should be stamped on the tin cover that goes over the pinion seal wouldn't want to pull it all apart to find 3.55  already in it  .......FC427.....

[newman]

You are right, I haven't checked yet I've got an old EJ workshop manual and it gives me a spec for the diff at 3.89. I'll throw it up on the hoist tomorrow at work just to check the centre if its stamped with a number or not, thanks for confirming that the rear univeral will be fine.

Mick 

[FB_MAD]

I've never owned an EJ and am happy to be corrected if I'm wrong but as far as I can recall the EJ's had the grey motor 3.89 diff centre as factory fitment.

If this is correct then it would appear that if your EJ is currently fitted with U bolts to hold the tailshaft uni to the pinion yoke and is also fitted with the red motor type rear uni joint then it may have been converted already to a red motor diff centre sometime in its pre history, and if so then in most cases the diff ratio can be found stamped into the steel dust/stone deflector that is press fitted to the pinion yoke in front of the pinion oil seal .

Scrape away any accumulated dirt and rust around this and you should in most cases find the ratio stamped into it.I have however seen some over the years that appear to have been missed being stamped in the factory showing no evidences of ever being stamped at all.

[mikey]

I've never owned an EJ and am happy to be corrected if I'm wrong but as far as I can recall the EJ's had the grey motor 3.89 diff centre as factory fitment.

If this is correct then it would appear that if your EJ is currently fitted with U bolts to hold the tailshaft uni to the pinion yoke and is also fitted with the red motor type rear uni joint then it may have been converted already to a red motor diff centre sometime in its pre history, and if so then in most cases the diff ratio can be found stamped into the steel dust/stone deflector that is press fitted to the pinion yoke in front of the pinion oil seal .

Scrape away any accumulated dirt and rust around this and you should in most cases find the ratio stamped into it.I have however seen some over the years that appear to have been missed being stamped in the factory showing no evidences of ever being stamped at all.

The first time I went to find out what diff ratio I had on my FC with a red motor and HR diff setup in it I did not realise that the steel ring had the ratio stamped on it.  I just jacked up one side of the car and put a mark on the wheel and tailshaft and just counted the turns.  Obviously just one wheel will turn twice as many times as if you had both wheels off the ground. 

Cheers   M