Swapmeet Gearbox . what to look for?

Is there a rudimentary test you can carry out to approximate the condition of a manual gearbox at a swap meet! This assumes the box is not apart and you are not going to open it up. Next . say it is open or you can open a side cover and peer inside it. What are you looking/listening/feeling (lol!) for and how do you go about it! I've got them before and they have for the most part been ok but its not due to me knowing what to look for - more good luck than anything else.

Good question.

I have done a few rudimentary things like turning the input shaft and trying to go through the gears while feeling and listening for any odd noises or crunching.(this can be hard work!)Finding out how many k's the car it came from had done,and looking at the oil in it. Water can cause problems if it has been sitting a while.

Not very helpful is it! I always think it is a bit of a gamble, but I ask the vendor what they know of the history and then make a judgement as to whether I trust them.

A gearbox with unknown provenance should have a suitably low price to reflect that.

Automatic transmissions are a total gamble in my view, best checked while still in the donor car.

Good Luck!

generally the weakest part of a manual gearbox is 3rd gear.

If it goes in and out of 3rd fine and you can turn the imput shaft and there is no huge amount of resistance then it should be okay,

The next part is checking the gates, Some time's it will not stay in a particular gear maybe due to worn pivot on the gear stick not engaging the gear properly.

wiggle the input and tail shafts for any play, in and out and up and down

Is there any excessive oil residue on the inside of the bell housing! sign of worn bearings which allows play and wears the oil seal down on the shaft.

if you want to see the condition of the oil in good light tip the gear box backward and let a little oil drain out around the tail shaft.

Tip it up side down and undo the sump drain/ plug(should have a magnet)

Fine particals of metal shavings are fine, from general wear and tear. any larger bitsstay away from it. If there is a mass of fine metallic shavings on the magnet it is a sign that the oil has not been changed in a long time.

Eyes can't tell much, your nose can detect the pong of hypoid diff oil which if present will have ruined the brass synchro hubs and/or the friction band in an overdrive.
The motor trade made a fortune from filling pommie car gearboxes with EP90 back in the 60's and 70's