Different diffs to suit BN1

[zblu]

Anybody know
where to get alternatives to the 4.1:1 pumpkins that are a straight change out for a 4 stud BN1 diff?

 

[Grantura_MKI]

Do you have any idea as to what ratio you are seeking?
Cheers, David. /ubbthreads/images/graemlins/patriot.gif

 

[pan]

The Austin A90 Atlantic had a 3.6:1 fitted as standard. I reckon they are getting a bit rare these days.

 

[Dave Russell]

The problem is that the earier 4 stud BN1 axles are a "spiral bevel" ring & pinion. Late BN1's & all newer Healeys had a hypoid ring & pinion & are completely different. I believe the A90 is the later type. From around car #221536, body #6478, November 1954, the change was made to the hypoid gear 5 stud axle. There just aren't many parts around for the early axle. I guess with enough work the whole rear assembly could be changed to a later model. Quite a few parts to change though.
D

 

[zblu]

That they are Pan, was just wondering if some of the commercials around at the time may have had ratios of use

 

[zblu]

Just looking around at the moment Dave Russell, mines the early diff

 

[BUNDYRUM]

Hello zblu & pan i have some information for you. Dave Russell, i have read your words of wisdom on a very wide range of subjects and was of the opinion that there was never anything to add after reading what you had to say. I certainly have respect for your obvious experience but here is something that i can add to even help you out with no malice intended. The Austin A90 Atlantic has the 4 stud rear end, but it's only the Convertible that had the 3.667 diff not the Hardtop, it had the 4.125 ratio which is the same as the early BN1 and also the Austin A70 sedans. The Austin A40 sedan has the same 4 stud diff but it's ratio is 5.125 and i don't think you want that. Non of the Austin commercials at that time had the same rear end and anyhow if you think of it you wouldn't want a commercial vehicle with a diff ratio of something around 3.6 as the motor wouldn't be able to cope with it. The 100/S had a 2.9 ratio listed but of course they are pretty much not available. About the only thing left to do is have someone make up a "new" set of gears to suit the original 4 stud diff as the people wanting 3.5 ratio diffs to suit the 5 stud diff did a couple of years ago. the only problem with this is getting the numbers to make it feasible cost wise. It would be easier to convert it to either a complete 5 stud assembly from the late BN1 onwards or something different altogether that would end up being lighter and parts easier to get. You just have to decide what your Healey means to you and go from there. The main argument against the 4 stud rear end is that if you want to put any sort of power through it on a regular basis then your still going to be stuck with poor quality axel shafts and the studs in the hubs coming loose/stripping out, narrow brakes and on and on. Having said all that i am reminded that a friend of mine did a lot of autocrossing/hillclimbing etc in his early BN1 back in the 70s' so once again it comes down to how sympathetic/hard you are with the clutch. I'm really enjoying this forum and not just from being able to correct people either. Regards to all, BUNDYRUM.

 

[zblu]

I had new axle shafts made up out of EN36A material, same as in CJ7 Jeeps, material has ability to
"wind up and then unwind", probably be the drive uni's go next!

 

[Dave Russell]

[ QUOTE ]
Hello zblu & pan I have some information for you. The Austin A90 Atlantic has the 4 stud rear end, but it's only the Convertible that had the 3.667 diff not the Hardtop, it had the 4.125 ratio which is the same as the early BN1 and also the Austin A70 sedans.

[/ QUOTE ]
Hi Bundy,
I did say that "I believe" the A90 is the later type. My "belief" was obviously wrong & I should have checked.

I should have said later type axles, Austin A99-A110, Wolseley 6/99-6/110 with Automatic Transmission are five stud, 3.54:1 ratio. I have one of these in my BN2.

Thanks for the corrections which are always welcome.
Regards,
D