Transmission Case Interchangeability

strum456

Member
I am trying to do a SOS swap in my 4000. I found a 3910 with good internal components, but the bell housing is cracked. The salvage yard doesn't have any other 4000 series tractors with 8 speed transmissions, so I'm trying to determine what models use that same case. It doesn't need to be a direct bolt in - I'm planning on taking the internals components from the 3910 and putting them in a good case.

PS:

I can't figure out classic view. When I try to post, I get a message saying that I need to be logged in (but I am logged in).
 
I assume that your 4000 with the S-O-S is the later 3 cylinder 4000, otherwise no tractor made after 1964 will have a transmission that will swap in.

It's best to find a complete rear half of a tractor that is known to be good, as the 3 cylinder 4000 S-O-S tractors had a differential with a different gear ratio (6.67:1) than the ones with the manual transmission (3.50:1), so the tractor will be too fast with a manual transmission if you simply swap the transmission without swapping the differential as well. Be sure to get everything from the flywheel on back from the donor tractor, as that will guarantee everything works together.
 
So here's the story:

I called the nearest salvage yard (1.5 hours away). They said they have a 3910. I stop on my way passing by to check it out. Looks good, very little wear. When I came back with the truck / trailer to get it, I noticed that the bell housing has a chunk broken out of it about the size of my hand. It's down low near the front radiating out from the two 3/4 mounting holes. The tractor was a former American Lincoln sweeper unit. I assume some part of the sweeper mounted to those holes and caused the bell housing to break.

Finding a trans / rear has not been easy, and I was already there, so I really wanted to get this figured out while I was there. The yard owner and I came up with a plan that I would take an other transmission as well to use for the case and swap out the gears from the good transmission with the broken bell housing.

It turns out that the transmission that I was going to use for just the case was full of water, froze, and has a big crack along the bottom.

I have since completely torn down the 3910 transmission. The gears and bearings are in very good condition; after all, how much abuse could a sweeper get?

Long story short, I have a really nice set of internal components and I just need a good case to put them in. Chances are, the same salvage yard has something that will work.
 

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