[Healeys] Gearbox

[John Harper]

Pat

Sorry but we cannot leave this uncorrected and mislead owners with wrong 
information. Many more parts are interchangeable than you indicate.

In general terms the BN1 and A70 and A90 Atlantic gearboxes are all from 
the same family. The BN1 is the same basic unit and was developed from 
the A70/A90 by fitting and overdrive. This replaces the whole rear end 
but also the third motion shaft which is unique to the BN1 and in short 
supply. There was obviously changes to fit side change parts but these 
are just bolt on and in any case Keith asked about gears.

There are two sets of first motion shaft, laygear and third gear that 
only mesh as a set and cannot be mixed. The later set was supposed to be 
stronger but this does not appear to be the case.

There are other things to watch out for. The main ones are that early 
A70 boxes had shorter first motion shafts. Also the A70 had only an 8" 
clutch whereas the A90 and BN1 have 9". To accommodate this a recessed 
clutch cross shaft is fitted.

There are other minor things to look out for but the message is never 
scrap an A70 or A90 Atlantic box.

Best regards
>
>Hang on to the A70 gearboxes. I am quite sure that the 1st/reverse idler
>gears are interchangeable, but the rest isn't.
>
>However all the gears from the A70 box may be fitted in place of the AH
>unit.
>
>Best wishes for Australia Day
>
>Patrick Quinn
>Sydney, Australia
>

-- 
John Harper