Gearbox numbers

[Jasper]

Hi
I have a spare gearbox that came with my 1933 10/4. It appears in good order. It has the number SYN6769A stamped on the removable cover for the gear lever, the same number on the gearbox itself. I am aware that my current gearbox in the car is a 2SYN. Would it be OK to replace it with the spare???

I am undecided at the moment because the one in the car wines a bit in 1st and reverse, but doesn't jump out of gear at all...Touch wood!! Also it is quiet in 3 and top. Gear changing can be a bit hit or miss with a bit of crunching!! Sometimes its fine and sometimes I wince a bit!!

I would prefer to keep the car as original as possible so next question, what is the spare one worth???

Hope someone can assist and thank you in advance

[peter_winney]

Jasper
It is possible that SYN6769A is the original gearbox for the car. If so it will have synchromesh only on 3rd and Top and not on 2nd. These boxes were fitted to chrome-rad cars from Aug '33 to July '34. They were an interim quick fix so Austin could claim "synchromesh" boxes across the range. With the low gearing of 10s most drivers start in 2nd on the flat or downhill. Synchro on 2nd was introduced in Aug '34 on the cowled-rad models.

The 2SYN box may have been fitted either because the existing gearbox was faulty in some way or the owner preferred the easier driving with synchro on 2nd. Things to check on your spare box is any play in the input or output shafts that could indicate wear in the bearings. If there is excessive play in the front bearing then the scroll-back oil seal will not work properly and you will end up with an oily clutch. If you want to test out the spare box you could swap it for the one in the car and see how it compares, then swap it back if you don't like it. There is a trick to this BUT if the box in the car is fitted with a carbon-thrust clutch release bearing (as fitted to 1936 model Lichield and Sherborne) it will not be easy to remove and replace.

Noisy 1st and Reverse gears are normal on cars that are approaching 90 years old but probably they whined when new as these are straight-cut gears. If they are very noisy then the bushes may be worn but replacing these will not remove the wear in the gears, so they will still be noisy.

Value? No idea, but it may be worth you keeping it as a backup in stock.
Peter W

[peter_winney]

Gear changing can be a bit hit or miss with a bit of crunching!! Sometimes its fine and sometimes I wince a bit!!

Avoid hurried gear changes and don't force the lever - give the ancient mechanism time to work.

[Jasper]

Peter
Thank ou so much for the comprehensive reply... I will stick with the one currently fitted and he spare is now on ebay

Kind regards

[bob_allison]

A bottle of Molyslip G will quieten that noisey gearbox .

[phil_taylor]

Hi J (do not know your name)
As Peter says the SYN gearbox is likely to be the original with no synchro on 2nd. The 2SYN gearbox is later than your car and the 2 shows synchro on 2nd gear. (Your ebay advert says the opposite?)
I would suggest the original (SYN) box was probably changed because 1st and reverse got very noisy as the straight cut gears wear through their case hardening so you get a harsh growling noise - particularly in 1st and reverse - as the smallest gears wear quickest. The only sensible solution is to find another box with less worn straight cogs and swap them. (The same applies to the 2SYN box in your car if 1st and reverse get very noisy.) I use later gearboxes in my 10 as I had quite a few spare ones in the past and could choose which to recondition and select the least worn gears when recommissioning an engine and box.
Best wishes
Phil

[peter_winney]

Pic to illustrate the small gears (also the gunge that can mess up a gearbox)

first-reverse.jpg (91.22 KiB) Viewed 64731 times

[peter_winney]

Concerning the numbers stamped into gearboxes it may often be the case that the lid of the box has been replaced and so has a different No than that stamped into the main casing. It will be the number stamped into the casing that will indicate what gears are inside.

In essence there are 4 types of gearbox for the Austin Ten

1. 1932-33 constant mesh helical gears but no synchro. Bell housing has open top and you can actually see the timing marks. Some say this gearbox is slightly longer than the later one but I have not done measured comparison
2. Aug 33 to Jul 34 - SN box - synchro on 3rd & top only. IMO the synchro is not as robust as later 2SN.
3. Aug 34 to mid 39 - 2SN box. synchro on 2nd, 3rd & top. From Aug 36 rear end plate had extension to take rear rubber engine mount for Cambridge, end plates are swappable. From sometime in 1938 the box was fitted with a front oil seal instead of relying on the scrollback.
4. 1940s models (Alligator Bonnet) had a bigger more robust gearbox with 2 pint oil capacity instead of 1.2 pint.

[phil_taylor]

The spiral angle of the synchro gears was altered in Aug 1935 so the 2nd and 3rd gears are different from the later ones. Found this out when mixing and matching a gearbox with a loose synchro ring.
Cheers