Allis 170 stalls

With rear wheels raised, I'll bet one goes forwards and the other goes backwards??  With the transmission in NEUTRAL, leave one rear wheel on the ground and the other one off the ground and I'll bet you cannot rotate the lifted wheel. This means the transmission is low on oil and the pinion (main shaft) bearings are welded together.

This repair requires removal of fenders, both rear wheels, both rear axles, hydraulic valve console and some lines, lift arm housing, 3-point hitch and finally splitting the rear end away from the dashboard area. I would flat rate this repair at 30 hrs of labor, which would include new brake bands, disc lining and springs. This is a pretty big deal and a good sized cherry picker and lots of blocking are needed.  Also figure out where the oil leak was that let the oil disappear. Replace the Oring on the PTO shifter lever while the tractor is split in two.

Then, what is the actual value of the tractor itself ??  If it needs 4 tires to be a "good" tractor, that's $1200 more.  If the transmission jumps out of any gears, now's the time to fix that.  Paying retail to fix something like this will probably exceed the tractors value for sure.

Good maintenance can save a lot of trouble and money. BTDT when I was a teenager and had my Dad's WD given to me, it started to squeak very loudly from the rear end while raking hay so I pulled the oil plug and not a drop came out. I had just overhauled the engine after the tractor had sat in the pasture for more than 10 years but never thought about the rear end oil. Did the rear end work myself though and even a WD is labor intensive and the amount of filings in the rear end was outrageous. Now, every time I use a tractor I check every oil level first and grease every zerk.

When I worked at a dealership, a guy locked up a D17 while driving down the road due to no oil in the rear end. He didn't want to repair it so the old mechanic there filled it with oil and rocked the one jacked up wheel until it broke loose. I don't know how long it lasted for that D17 but the old mechanic there said there were lots of WD tractors out in the country that had that very same non-repair done to them. I wouldn't do it though and it would be on my mind if I sold it that way to an unsuspecting buyer.

OP says it goes into all gears fine.  Wouldn't a shift fork problem at least fell funny on the lever???