[Healeys] Overdrive ratios

[Michael Salter]

"That should be added to the concours guidelines!"
Unfortunately,  as is the case with thousands of other details, the addage "If I can't see it, I can't judge it" applies to the overdrive ratio.
The Concours Guidelines are at a very critical point.
Current technology is such that there is virtually nothing in the Guidelines that cannot be determined by simply enquiring of AI.
Give it a try, you'll be stunned at the detailed answers that it produces.




________________________________
From: Alan Seigrist <healey.nut at gmail.com>
Sent: Thursday, 16 July 2026 10:17:54
To: Harold Manifold <manifold at telus.net>
Cc: Robert Markovich <rmarkovich at aol.com>; healeys at autox.team.net <healeys at autox.team.net>; Michael Salter <michael.salter at gmail.com>
Subject: Re: [Healeys] Overdrive ratios

That should be added to the concours guidelines!

On Wed, Jul 15, 2026 at 8:46 PM Harold Manifold <manifold at telus.net<mailto:manifold at telus.net>> wrote:
Hi Michael,

I have attached a document from my archives regarding this topic. I believe the information in it agrees with Hank's previous comments.

Best regards,
Harold

On Wed, Jul 15, 2026 at 4:17 PM Robert Markovich via Healeys <healeys at autox.team.net<mailto:healeys at autox.team.net>> wrote:
I thought they did use a .77 overdrive on the 100/6 as on the 100 BN2, but lessened it to a .82 (or so) unit on the 3000s. Along with a rear gear switch from 4.10:1 to 3.90:1.


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On Wednesday, July 15, 2026, 2:29 PM, Michael Salter <michael.salter at gmail.com<mailto:michael.salter at gmail.com>> wrote:

As I recall Hank the 100/6 also used the 28% overdrive, the same unit as the BN2.

M


________________________________
From: Hank Leach <gradea1 at charter.net<mailto:gradea1 at charter.net>>
Sent: Wednesday, 15 July 2026 13:47:08
To: Michael Salter <michael.salter at gmail.com<mailto:michael.salter at gmail.com>>; healeys at autox.team.net<mailto:healeys at autox.team.net> <healeys at autox.team.net<mailto:healeys at autox.team.net>>
Subject: RE: Re: [Healeys] Overdrive ratios

Overdrives for AH 100 were installed as follows:
OD 1260 (32%) was used up to 140204 (not practical in use)
OD 1292 was used on chassis 140205-228046
OD 1308 started at 1 to 228046
OD 1447 was used on chassis (BN2) 228047-230489 (with some exceptions)

Later cars, including BJ8 went to a 22% unit.

--------------------

From: "Michael Salter" <michael.salter at gmail.com<mailto:michael.salter at gmail.com>>
To: <gradea1 at charter.net<mailto:gradea1 at charter.net>>, <healeys at autox.team.net<mailto:healeys at autox.team.net>>
Sent: July 15, 2026 at 9:35 AM PDT
Subject: Re: [Healeys] Overdrive ratios
Thanks Hank. Very much appreciated.

M


________________________________
From: Hank Leach <gradea1 at charter.net<mailto:gradea1 at charter.net>>
Sent: Wednesday, 15 July 2026 12:33:04
To: Michael Salter <michael.salter at gmail.com<mailto:michael.salter at gmail.com>>; healeys at autox.team.net<mailto:healeys at autox.team.net> <healeys at autox.team.net<mailto:healeys at autox.team.net>>
Subject: RE: [Healeys] Overdrive ratios

Michael- the 1260 is the early 32% OD. The 1292 is the 100 common 28% ratio. After that ODs for BN2s were 1308-28% and 1447-28%.

I actually have an OD case #105 but 288 is a low serial number. Regards, Hank
--------------------

From: "Michael Salter" <michael.salter at gmail.com<mailto:michael.salter at gmail.com>>
To: <healeys at autox.team.net<mailto:healeys at autox.team.net>>
Sent: July 15, 2026 at 9:22 AM PDT
Subject: [Healeys] Overdrive ratios
I have 2 BN1 overdrives which I'm struggling to identify.
Unlike the later type "A" units the serial number on these is not prefixed with the ratio.
The serial numbers on these are :
1260/288
and
1292/2037
Anyone with information which would help identify the ratios of these?
Thanks.



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