i have a old sears 536.909400 snow blower , i removed the shear pin and one side of the auger is froze up , whats the best way to free it

Heat...a lot of heat. But...you could try soaking it with a rust-busting / penetrating fluid. The key to those working is time - you have to allow it at least a day, more with very rusted up things.
If you use heat, and you'd have to use at least MAPP gas, but preferrably an oxy-acetelyne torch with a rosebud head. Propane doesn't usually cut it with rusty, stuck-together things.
But take note, if there's a seal in the gearbox on the auger shaft, you'd probably have to replace it when done, which may or may not require removing the entire auger drive assy. from the unit. If you want to pull it out for any reason and don't know how, just ask.
My experience with augers being rusted on the shaft is that it is a very tough challenge to free them up. Can be done, but it's an uphill climb - usually. All depends on how long it's been stuck, and if it was ever greased (some better/older units have zerks on the rake tubes).
Paul

thanks paul , tried taking it apart split gear box was'nt able to get it free ed up was just happy to get it back together.one side is free replace both shear bolts guess ill hope for the best.

Ahh, now if you can only avoid those pesky unseen, beneath-the-snow newspapers, tree limbs or flat, frozen squirrels (had one come in with that once from the street-plowed-up stuff someone was clearing LOL).

Leave the shear-bolt out of the stuck side - this way the rust will act as a shear-bolt with any luck!

Ahh, now if you can only avoid those pesky unseen, beneath-the-snow newspapers, tree limbs or flat, frozen squirrels (had one come in with that once from the street-plowed-up stuff someone was clearing LOL).

Leave the shear-bolt out of the stuck side - this way the rust will act as a shear-bolt with any luck!

how easy is it to get pats for this blower im sure it is about 30yrs old , and where do you get them from. thats another reason i dont what to tear in to it to much

how easy is it to get parts , im sure this blower is 30yrs old , and where do you get them from, thats another reason i dont want to tear into it to much

It was mfg. by Murray. Briggs now owns Murray, I checked a few part numbers, doesn't look good - all were NLA except shear bolts which changes part numbers a few times.
Any B&S dealer can help you get the parts you need, if available.
You can go on Sears website, plug in the model number and it'll bring up IPLs (parts lists) with diagrams too. Take the part numbers, and call a Briggs dealer.
Paul