Have a gearbox I need to identify. Its a drummer with the code
AM 331 11 92

anyone know what it is

Cast in numbers?

Thats the part number for the lid mine is 331 11 81 think the last two numerals were the revision numbers .

think it had paint stamp to identify the contents

The late Jeroen cats website had good box identification section

Sean

Paul,
have you checked for rings engraved on the input shaft?
No ring = 2CV ratios
One = Dyane/Ami
Two = 2CV4/ certain fourgonettes

Failing that, it's lid off and counting of teeth, but size of the brake drums should also help...

ken

Also you should find 2 circles, size of a coin, stamped on the side of the gear box. They will give your the Year and Date (production details)

Been caught on counting teeth on my AK 400 input shaft. 2CV6 and 400 both have 19 teeth but not the same diameter.

Thanks all. I have not seen this box, its in a mates car. It has the larger drum brakes [220]. The problem is that his car won't do more than 90kph without the engine screaming its nuts off.

I suspect its a van box shoved in a car and that the ratio's are wrong however the various types of gearbox ratio's have always been a bit of a magical mystery tour.

Was hoping that there was a clever and easy way I could advise him.

Check all wheels are running free. If 1 wheel cylinder is stuck, the brakes are holding back the car. Seen wheel bearings do the same thing.

Paul,
sounds very much as though it's a low ratio box.
Easiest way to check the ratios is to jack the front end off the ground, engage 1st gear, remove the plugs and wind the engine over with the starting handle, counting the engine turns needed for one complete revolution of the road wheels.
Low ratio box = 28.7 turns
2CV = 21.5,
Dyane/Ami = 22.3.

Viking,
as long as that Pembro chappie (or his French counterpart) hasn't had his paws in there, mixing and matching ratios, the 3rd gear pinion in the 2CV box would have 14 teeth, whereas the low ratio box would have 15...

ken.
( p.s. Paul, that 'multi yellowed' 2CV which my pal Andy Cartwright bought off Leboncoin turned out to have a 2CV4 box mated to a 602 engine.
Apparently, it wasn't too much fun on the trek to Most and back, but it did surprisingly good mpg. )

Didn't see Andy in Most, I might have chuckled. Thanks for this Ken I'll pass it on.

Of cause that is a possibility but I doubt it. Who are you referring to as Rick’s counter part in France? It could well be a straight 4 box, if yes 90 clicks or thereabout would be right.
Another theory would be the beginning of a sliding clutch. You never really know until test driving the beast yourself. It is hard to be a mechanic in front of a computer