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Old 31-10-21, 10:16 PM
Julian Caples Julian Caples is offline
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Join Date: Oct 2009
Location: Melbourne, Australia
Posts: 26
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Glenn

It does seem likely that you have a first gear from an AC Ace or one of the replacements that was made in the 80s or more recently
These are higher in ratio (2.92 vs 3.61 - lower number=higher ratio) and "fixed" in that they have neither the freewheel nor synchro

The "fixed" bit means that they engage by simple dog teeth with no means to match gear shaft speeds (synchronise). Engaging at low speed is possible without double declutching, or you could double declutch

They are helical gears (not straight cut) - there was (and is) no reason to make them straight cut, and as has been pointed out a straight cut gear will scream.

The Bristol "fixed first" were not modified conventional first gear sets, but properly done first gear and layshaft pairs (you need the matching layshaft) as the ratio was changed (as were sets done in the 80s and more recently). In theory it would be possible to modify a freewheel gear (to fix it), but it would be a bodge, would be hard to get to work properly, and wouldn't change the ratio.

The higher ratio would be perfect for the FN, the lighter car would be woefully undergeared in first, particularly if it still wears the 4.22 ratio diff from the 405
The FN (and all AC Ace/Aceca) had the higher ratio first ex factory

Cheers

Julian
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