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Gearbox numbers

Posted: Thu Oct 14, 2021 2:20 pm
by Jasper
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

Re: Gearbox numbers

Posted: Thu Oct 14, 2021 6:06 pm
by peter_winney
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

Re: Gearbox numbers

Posted: Thu Oct 14, 2021 6:53 pm
by peter_winney
Jasper wrote:
Thu Oct 14, 2021 2:20 pm
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.

Re: Gearbox numbers

Posted: Thu Oct 14, 2021 7:42 pm
by Jasper
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

Re: Gearbox numbers

Posted: Fri Oct 15, 2021 2:25 pm
by bob_allison
A bottle of Molyslip G will quieten that noisey gearbox .

Re: Gearbox numbers

Posted: Fri Oct 15, 2021 7:12 pm
by 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

Re: Gearbox numbers

Posted: Fri Oct 15, 2021 8:05 pm
by peter_winney
Pic to illustrate the small gears (also the gunge that can mess up a gearbox)

first-reverse.jpg (91.22 KiB) Viewed 4095 times