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Diff ratio

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57_BN4

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Hi again,

While I am digesting the consequence of forking out 10k for a new chassis, in the other workshop the mechanicals are coming apart one by one. Last night I pulled down both diffs I have- a 3.54 from an Austin sedan of some sort, and the 4.1 from the car, unopened since 1957. The sedan diff seems to have been used for burnouts as the cross pin was seized to one spider gear and had sheared off the retaining pin. This left the shaft retained only by the seized-on spider gear and so has worn the holes in the cage housing very oval. Hopefully the main gears have survived ok.

Is the general consensus still that 3.54 is the better ratio for a BN4 with OD? My Zephyr has a 3.9 + OD and I wouldn't want any taller as it only has 3 gears and often requires first gear on-the-fly. Does first gear get used much in a Healey?

Second potential option is a Quaife helical gear ATB
129219884.jpg


I have no intention of competitively racing the car but what effect/improvement would an ATB diff make to enthusiastic driving? I spent a couple of years tootling around in a Triumph Vitesse and would have happily killed somebody for an LSD at times due to their silly-swing rear suspension. What is the Healey like for lifting the inside tyre in a corner?

Appreciating your help,
Andy.
 
Is the general consensus still that 3.54 is the better ratio for a BN4 with OD?

Yes it is a step up in the right direction.


. Does first gear get used much in a Healey?

Not if you have the 4.11 diff installed.


-----------------Keoke
 
I have a 3.9 with OD and recently have quit using 1st gear except for starting on steep hills. It saves a lot of potential grinding -- I routinely shifted into 2nd gear before engaging 1st, now I just keep it in 2nd gear.
 
Hi 57
I use a clutch type LSD w/4.1 and do some spirited driving on the twisty's
I will never go back to the stock set up.
I find the LSD to be a HUGE improvement
This winter I plan on rebuilding my 3.5 w/lsd
The 4.1 is quicker off than the 3.5 but the lower ratio has many advantages
All healeys want an LSD
 
Andy,


I have a 3.54 ratio in my Healey with out OD and it drives great at Highway speeds 65-70 mph. You could really cruise at a low rpm with the over drive but I think its fine even without it.

Bob
 
I find the standard 3.77 ratio of my o/d BJ8 is ideal for all but 100mph plus continuous running. Given your roads in NZ I'd go for the 4.1. I'm not sure if they fit in your car but the bees knees is a set of Tulip gears, six perfectly spaced ratios; 1,2,3,3o/d,4,4o/d.
 
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