Ford SOS to 5 Speed

I have a 961 and an 860 and love both. I also have a 64, 4000, 4 cylinder with SOS. I love the 4000 even more.

Dean

If you are not afraid of getting into an automotive automatic transmission there is nothing inside an SOS transmission that should deter you.

There are several on this board who can offer advice and most parts are still available from CNH but often expensive (sometimes very expensive).

I highly recommend that you buy a proper Ford SOS manual before getting into it or even deciding that you must. Some things are not intuitively obvious and you can damage things that are very expensive unless you have the proper manual.

Good luck with your project and post back if you need advice.

Dean

I am confused. Why do you say a 5 speed won't work? The gearing in the trans is constant across all aplications. Changes in gearing to account for row crop, or utility were all done in the differential. Or have I slipped a cog in the brain case?

Bob,

You have 3 problems

1) the brakes for the 850 had the left brake going thru the trans. Your brakes are going thru the differential. Not a big problem, but you will have to cover the holes in the trans bell housing.

2) The output shaft on the SOS is 23 spline and the output for the 850 is probably 10 spline. If you do the swap, you will need to cut both couplers in half and weld up a hybrid coupler. Have a competent welder do it so they are true - if you don't have the skills yourself.

3) the engine plate for the 850 is probably thicker than the plate for the SOS. Be sure you use the correct one.

My opinion (for what that's worth) is that you should change the input and output seals and check the bearings on the 5 speed while it is out. Much better than finding out you have an issue 2 weeks after completing the split!

jb

Yes, the transmission will work. The transmission gearing is no different but Bob asked about using the complete transmission and rear end from an 850 on his 4 cylinder 4000.

Because the row crops have final reductions they have a smaller differential (6xx?) with a higher gear ratio.

Though I cannot say with certainty that the 850 rear end will not bolt to the final boxes, the tractor will operate much slower with the lower differential gearing of the 8xx.

Though I have not had a row crop final reduction box apart, I suspect pect that it uses a single pair of spur gears. If so, the 9xx tractor with an 8xx rear end will have 5 reverse gears and a single forward gear.

Again, I have not verified this but I suspect that the 9xx differentials have the pinion gear on the opposite side of the ring gear relative to the 8xx differentials in order to drive the axles in the opposite direction.

Anyone tried this?

Dean

OOPS!

I missed that part about "and rear end". Thanks for straightening me out.

I have taken apart 960 differentials and they do have the R&P on the other side and a single spur gear - resulting in a 1F/5R operation with a diff housing swap. Thankfully, the 850 differential housing uses a larger diameter axle trumpet - so they can't bolt up.

Here's a thought... He could bolt up the 5 speed and entire rear end. The front would sit too high, but he could either get (much) smaller diameter front tires or larger diameter rear tires.

Of course, best option is to just fix the SOS - next best would be to just swap the transmission. I think the loss of the live PTO would be a long term disappointment.

jb

I have a very close and trusted friend about 80+ years who is very knowledgeable about many things. Indeed, he is the only guy I know that still pours and fits babbit bearings.

He told me an interesting story about a time when he was about 18 or so and had differential problems on a mid 30s Plymouth. He worked under the car over a ditch in the snow to remove the punkin to repair it. Turns out, the punkin in this car was symetrical and when he installed it he put it in upside down.

When he stated the car up he was shocked to find out that he had 1 speed forward and 3 reverse. He tells me that it was fun initially but quickly became boring.

Dean

I have a buddy that built a street rod back in the 50's or early 60's. He put in a GM steering box, but on the wrong side of the frame so when the wheel turned left the car went right. As that was his only transportation, he had to drive it 3 days until he could fix it. From the way he tells the story, I don't think he was bored at any point!

jb

That's scary. I think I'd rather drive with one speed forward and three reverse.

Dean

No. The 5 speed transmission will work but you will need a rear end unit from a row crop tractor.

The row crop tractors have a final reductions and a smaller differential with a higher gear ratio.

Dean