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+--- Thread: Gearbox syncro confusion (/showthread.php?tid=9768)
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Gearbox syncro confusion - GM6VXB - 18-12-2024
Confused myself again (not difficult), but had the top off the gearbox to cure a small leak.
Looking into the gearbox I notice THREE syncro rings. This would explain why changing up or down
into second does not go with a crunch, or am I just lucky !.
This is where the confusion comes in. At the front of the top cover it is marked 2 SYN 181. Now I
thought this meant the gearbox had two syncro rings for 3rd and 4th but maybe I am wrong.
Also I thought the three syncro box was not introduced until 1934, which is a year after my car was
first registered.
Maybe the car has had a replacement gearbox at some stage, but can anyone confirm I have dates
for the three syncro box correct and that the 2 SYN number is for a two syncro box.
Martin.
RE: Gearbox syncro confusion - Reckless Rat - 18-12-2024
My understanding was that the first synchro boxes were stamped SYN and the later ones, which has synchromesh on 2nd, 3rd and Top were stamped 2 SYN.
RE: Gearbox syncro confusion - Chris KC - 18-12-2024
I think Reckless is right, but also that what's on the lid may bear no relation to what's inside - the SYN and 2SYN tops are interchangeable.
I'm attaching a pic of the gear clusters from a SYN box, with synchro on top and 3rd, which may help you determine what you have.
RE: Gearbox syncro confusion - David Stepney - 18-12-2024
2 synchro boxes were first introduced on 22nd July 1933. The 3 synchro box was introduced on 7th July at the introduction of the first low chassis (Ruby) saloons. It looks as if you car has had a later replacement box fitted.
RE: Gearbox syncro confusion - GM6VXB - 18-12-2024
Thanks all.
Looks like the gearbox has been replaced. The car was first registered in June 1933
so probably too early for the three syncro box to be fiitted so retro fitted probably in
the 90's when a lot of work was done on the car.
Not able to take a decent picture as the box is in the car and camera won't focus.
Martin.
RE: Gearbox syncro confusion - Reckless Rat - 18-12-2024
I agree. Your car would have originally been fitted with the four speed crash box ( like mine). It's a good box, very tough, but slow. I'm sure many were replaced with the more user friendly synchro unit. Nothing wrong with that IMHO. I did try one but it was rubbish ( worn out synchros noisy and vibrations) so I reverted back to the original one.
RE: Gearbox syncro confusion - Parazine - 18-12-2024
I've found, over the years that the 4 speed crash box is actually the nicest to use - if you can cope with double de-clutching all the time The 4 speed synchro is very prone to baulking (i.e. the striking dogs meeting head on, preventing engagement) when the synchromesh is working and also prone to the synchromesh wearing out (which cures the baulking problem). The gearchange is also heavy and ponderous in my view. The crash box is a little slow but the change from 1st to 2nd is usually very slick and the whole unit is beautifully (and no doubt, expensively) engineered, with chevron gears, to cancel out the end thrust produced by the helical cut pattern. The crash box is light and easy to use, once you get used to it.
However, the 2 and 3 synchro boxes were probably cheaper to manufacture, even after paying the royalty to GM for using their patented gear synchronising invention.
Baulking was a feature of all the Austin gearboxes, right through to BMC days, the 803/948cc A30/35, Morris Minor etc. gearboxes all suffered in the same way. Eventually, for the 1098cc and subsequent gearboxes, baulk ring synchromesh was added, which cured the problem by allowing the striking dogs to slip past each other if they met head on. It was possible to replace the baulk rings to restore weak or worn out synchromesh as well - a much improved gearbox.
As Reckless says, 2SYN is Austin shorthand for "synchromesh on second".
RE: Gearbox syncro confusion - Colin Morgan - 18-12-2024
I seem to remember that the '2-sync' box (2nd, 3rd and 4th) can be identified once the lid is off by the half moon cut-out in the top flange seen on the right in this picture?
A7 4-speed 2-Sync Gearbox.jpg (Size: 97.44 KB / Downloads: 220)
The picture is from the Devon club site:
http://www.da7c.co.uk/technical_torque_articles/austin_seven_gearboxes.html
RE: Gearbox syncro confusion - Dave Mann - 19-12-2024
I'm non too keen on the 3 synchro boxes after one locked up on me, it was locked in gear with the transmission locked, I picked the rear up and wheeled it into a car park to deal with it. I know of at least two other instances.
RE: Gearbox syncro confusion - Colin Morgan - 19-12-2024
Did you work out the cause?