What's a sideshifter trans in unknown condition worth?

If it is all there and not frozen... $150 as a core IMHO.

And if I pop it open and the gears are all good?

What do you think it’s worth as is? You must have some number in mind.

It’s not the gears that go bad
It’s the syncros. And sliders

Kinda hard to see slider condition if it’s your first time
Need to know what to look for on the slider

Just pop off the back cover and check the teeth on the first gear slider. If they still have points the trans should be in good shape. Also check the drain plug for metal shavings.

You’ll have found the unicorn!

Well the number that came to mind is $300. Providing no chipped teeth,etc. All those gear sets don't just magically appear when you need them. It is a 50 year old German sports car. I was looking at $2500 to have a very good shop rebuild my tailshifter. $300 for a good usable core seems cheap . But those guys build race car stuff. California Motor Sports. On a side note, I think I bought a windsheid from you ages ago.

One can hope.

@orangecrate - Contact Dr. Evil for a good valuation and his rebuild estimate cost. He does good work and knows these 901's inside and out.

Cores are just that. I buy them for $150 all day long, every day. I see them offered at $300-500 all day every day, but dont see them selling. Price is subjective as I am not, as a retailer and rebuilder, going to pay high prices for cores. I tend to buy in bulk so 10 at a time. That is one way I get a discount. I dont sell cores, typically. I use them to repair others and plan to start building ones for sale on exchange this year. With parts sales, go to the parts section here, and see what old ads went for. That will give you an idea. You are also in AZ, so more cores there that are likely in better shape so hard to sell local for more. People in the rust belt pay more for parts, but then shipping kills your sale.

If you open it, you may make it worth less to the next guy who has to assemble it. Thats the rub. You also need to know how to inspect it to see what parts are worn. The concept that if 1st is good then all is good is bunk. Plenty of proof of that out there. Many people address 1st, and that is it, and the rest is left to wear out.