What diff ratio do i have

[Fishyweare]

has a couple of numbers stamped in but nothing that makes sense to me , has 35 teeth so does that mean its a 3.55 if so how much difference would a 3.36 make as the car seems to scream just trying to get to 100 km hour, ek wagon 13 inch wheels don't want to change to 14 inch .
at the moment speedo read 60 m/h = aprox 85km/h actual
cheers
paul

[rosco]

Hi Paul - you've probably done this - with little joy..... but all later model diffs had the ratio stamped into the flange plate (behind uni joint receiver on diff centre).
If you don't have anything stamped - I'd guess that it's the original 3.89:1... and yes, at 60 mph, your doing 3,200 rpm on 13" wheels with approximately the same circumference as the original 13 x 6.40 cross plies....

The most accurate way of identifying the ratio is to count the crown-wheel teeth and divide it by the pinon teeth (calculator will remove all arithmetic errors)..... sometimes, an incorrect flange can be fitted and fool everyone....

If you are an auto with a grey - 3.36 will take the bite out of your engine - but will give you a lot lower rpms.... and more than likely a much better fuel economy on long runs...... forget 3.08 - it's far too tall for a stock grey motor.
Many put 3.55's in.... behind Ek hydra's and the later T"raumatics".... I actually like the 3.36...... it was an "option" in the EH range - and the first which afforded the first 100mph Holden...something is nagging that it was the diff ratio for the 4 speed EH auto's.... yes, they were 4 speed! - EJ only got the same as the EK - but EH got four... then HD went back to the strongest Holden box ever.... the Power-glide.... Traumatics came from HG onwards until the Crummydores arrived....I lost interest after that... if it wasn't for Brocky - I probably would have dropped out of any Holden hype.....

frats,
Rosco

[rosco]

Sorry, Paul - something hit the "auto" receptor and I may have belittled you as having an auto.....

Ok - 85 km/h actual - showing 60 mph indicated - what tyres have you got fitted and what is the "rolling circumference"?

If you are manual - and you can find a good 3.36 - go for it.....

I had a 3.55 in mine with a 179 c.i. motor and 4 speed.... waste of time slotting up 2nd unless towing.... 1st to 3rd changes were common ... until - I fitted the 3.08... I now have to use 2nd to get to third....

If you're manual - and stock grey - either the 3.55 or 3.36 will suit... but I believe your tyres are under-rating your drive line.... and if you like the tyres your using.... I'd suggest the 3.36....

you can get different drive cogs for your speedo driven gear.... well, you can with the Warner boxes... I don't know about stock ones....
I just found the cog which brought me closest to actual and made the mental adjustment for error after that.... I'm 5 mph slower than indicated..... Navman is a great companion...

frats,
Rosco

[Trev]

Have another look on that cog, I always have found the ratio on there, it may be a bit faint but it should be there.

[Fishyweare]

Cheers all checked the pinion and did the old sums and yes it is a 3.89 but definitely nothing stamped

Now to find a good 3.36 have a couple to look at on the other side of town out of a ht .

Question
1. I am going to buy another yoke will this go straight onto a diff from a ht or am I better off to have my tail shaft adapted and use ht universal joint .
2. Or can a ht tailshaft be used with the old standard gearbox ?

Cheers
Paul

[Mick]

I'm pretty sure as you've found out 3.89 aren't marked with a ratio
I'm pretty sure you can't change the yolk but you just change the uni in the tailshaft and get U bolts

[rosco]

Paul, when I did mine - as Mick states, all I had to do was fit a uni joint with "U" bolts connecting the diff yoke to the Uni spider.
I didn't get to use it - as I removed the grey gearbox during the process of fitting a "red" motor and went with the 4 speed Aussie instead....
As I remember - the tailshaft length was the same with the 3.55 centre in an EH housing - as was the original EK gearbox and diff..... but I'm hoping others will chime in and tell you the same thing....
I had to fit an LJ auto Torana tailshaft to match the length needed from the EH housing to Aussie box.....
I believe all post-EK diff centres have the same housing flange to Uni joint lengths.... my 3.08 coarse spline was exactly the same as the 3.55..

frats,
Rosco