Looks like an excellent job you did there! Not an easy task, but sure looks good!
646 Power Steering Conversion
After combing though a bunch of discussions on this subject, I thought I'd share my conversion and things I've learned along the way. The way I did required a lot of custom fab work so it probably won't be for most people but maybe someone will find some use in it. If anyone has any questions I'll do my best to answer them!
The steering valve is a Danfoss OSPM 100 PB I got from ebay, this one is from a John Deere 7700A (JD# TCA17008). The PB models have a power beyond port which I just tee'd into the return line right below the unit. If you find an ON unit instead of a PB you can avoid having to do that, they are identical minus the 5th port. The 100 is the displacement and has worked out to a good match. An 80 would take more turns, a 50 would be too small for the ram I used. The body diameter is small enough that it fits in dash without moving the levers when moved forward about 3/8" from the original location. It's mounted from the bottom of the dash with a 1" spacer which leaves it a little higher than the stock wheel which I think makes a better location overall.
The priority valve is a Buyers Products HFD075, again, cheap from ebay. I put it in between the travel valve and the loader valve so it isn't robbing flow from the travel motor which needs all the help it can get. It's physically quite large but it's pretty much the smallest I could find without spending a fortune. The original line was just cut and flared and left in is normal place. Bending up the tube to go from the priority valve to the loader valve was a real pain because it barely fits but the rest of the lines were pretty straight forward.
The ram I had left over from an old commercial tire change machine I dismantled. It's 2-1/8" bore and 1" rod. I shortened it to about 3.5" stroke and added spherical bearings to both ends as well as custom ports. I've seen lots of talk about using 648 parts but one of the things I haven't seen mentioned was that the B48M motor mounts are way higher than the CCKA. This means that there is very little room for the ram. To get it to fit I cut had to cut a part of the frame out at the lower, back end of the cylinder. Even still at various points in the steering/axle articulation it just barely rubs on the front motor mount bolt, the frame rail at the front motor mount, and the steering main arm. This is also the reason for the hydraulic ports. I probably could have just pulled through hoses but they would have rubbed on a ton of stuff and I didn't want that.
Anyways, some pictures!
The original cylinder
![Road surface Asphalt Automotive tire Gas Composite material]()
Bored out for a spherical bearing
![Automotive tire Gas Auto part Automotive wheel system Rim]()
Threading the cylinder rod
![Motor vehicle Automotive tire Machine tool Engineering Gas]()
Shortened ram
![Asphalt Automotive exhaust Road surface Cylinder Gas]()
Welded up with the new ports
![Gas Engineering Machine Metal Auto part]()
My JIC flare tool (punch not pictured)
![Drill Wood Gas Tool Electrical wiring]()
![Yellow Automotive design Wood Bumper Hood]()
Cad model of the short tube. It helped a little but I still made it wrong the first time haha
![Grey Art Creative arts Font Tints and shades]()
Home made tube bender
![Automotive tire Motor vehicle Wood Bicycle tire Automotive wheel system]()
The original loader valve feed line
![Wood Gas Bumper Automotive exterior Metal]()
Priority valve installed with the short tube. The tube at the rear is pressure to the steering valve
![Automotive tire Bumper Gas Wood Engineering]()
Steering valve installed in the dash
![Wood Gas Machine Metal Engineering]()
Ram installed in the frame
![Tire Wheel Motor vehicle Vehicle Automotive tire]()
And a video of it working! Probably the best upgrade I've made, it makes it so much more pleasant to run
The steering valve is a Danfoss OSPM 100 PB I got from ebay, this one is from a John Deere 7700A (JD# TCA17008). The PB models have a power beyond port which I just tee'd into the return line right below the unit. If you find an ON unit instead of a PB you can avoid having to do that, they are identical minus the 5th port. The 100 is the displacement and has worked out to a good match. An 80 would take more turns, a 50 would be too small for the ram I used. The body diameter is small enough that it fits in dash without moving the levers when moved forward about 3/8" from the original location. It's mounted from the bottom of the dash with a 1" spacer which leaves it a little higher than the stock wheel which I think makes a better location overall.
The priority valve is a Buyers Products HFD075, again, cheap from ebay. I put it in between the travel valve and the loader valve so it isn't robbing flow from the travel motor which needs all the help it can get. It's physically quite large but it's pretty much the smallest I could find without spending a fortune. The original line was just cut and flared and left in is normal place. Bending up the tube to go from the priority valve to the loader valve was a real pain because it barely fits but the rest of the lines were pretty straight forward.
The ram I had left over from an old commercial tire change machine I dismantled. It's 2-1/8" bore and 1" rod. I shortened it to about 3.5" stroke and added spherical bearings to both ends as well as custom ports. I've seen lots of talk about using 648 parts but one of the things I haven't seen mentioned was that the B48M motor mounts are way higher than the CCKA. This means that there is very little room for the ram. To get it to fit I cut had to cut a part of the frame out at the lower, back end of the cylinder. Even still at various points in the steering/axle articulation it just barely rubs on the front motor mount bolt, the frame rail at the front motor mount, and the steering main arm. This is also the reason for the hydraulic ports. I probably could have just pulled through hoses but they would have rubbed on a ton of stuff and I didn't want that.
Anyways, some pictures!
The original cylinder
Bored out for a spherical bearing
Threading the cylinder rod
Shortened ram
Welded up with the new ports
My JIC flare tool (punch not pictured)
Cad model of the short tube. It helped a little but I still made it wrong the first time haha
Home made tube bender
The original loader valve feed line
Priority valve installed with the short tube. The tube at the rear is pressure to the steering valve
Steering valve installed in the dash
Ram installed in the frame
And a video of it working! Probably the best upgrade I've made, it makes it so much more pleasant to run
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Wow.. I can tell you like to do things the hard way 
but what you came out of it with looks fantastic. I think there's a big overlap between being very particular about what you want, and ending up with the skills to do it your dang self because noone else will care enough to get it 'just so', exactly like you dreamed it up. I have welded on a cylinder but sure never shortened one yet, and i haven't 3d modeled a small tube so i can't say im there yet, but i definitely relate to the level of demanding things from your own projects that leads you down the rabbit hole to eventual '100% custom' bliss. Nice work, thanks for posting it up!!
but what you came out of it with looks fantastic. I think there's a big overlap between being very particular about what you want, and ending up with the skills to do it your dang self because noone else will care enough to get it 'just so', exactly like you dreamed it up. I have welded on a cylinder but sure never shortened one yet, and i haven't 3d modeled a small tube so i can't say im there yet, but i definitely relate to the level of demanding things from your own projects that leads you down the rabbit hole to eventual '100% custom' bliss. Nice work, thanks for posting it up!!
Late replies, busy driving tractors, you know how it is
Thanks for all the positive comments! I'm glad others like it. After running it for a month, everything is working great. I was concerned the 100cc steering valve would be fast and cause the steering to feel twitchy but it's actually perfect. Any smaller would be a lot of cranking going from lock to lock. The loader is a little slower with the priority valve stealing some flow but it's not bad. I have a slightly larger pump than the factory one in it anyways so it's probably running the way a stock one would anyways, I just got used to the speeeed.
I did also underestimate the amount of play in the front axle when I measured everything up. I think I originally said I made the ram 3.5" stroke, but it's closer to 3.25/3.38" somewhere in there. Probably should have made it 3.63". Anyways, I cut about 1/2" out of the steering arm at the axle to get a little more throw and now I have about 95% steering travel so I'm happy with that. It's actually has more steering angle now that it ever did with super sloppy manual steering.
What a pain those things are to make, you couldn't pay me enough
There are companies around that will bend them up if you bring in a sample. Talk to your local hydraulic supplier if they don't do it they can probably point you in the right direction
The drain to the machine is tee'd into the return line between the TCV and the loader valve. I just drilled a hole and tig welded a small piece of tube to it with a ORFS end. You can see the hydraulic hose in the bottom right of the video at about 23 seconds in, that is the return. The power beyond and the tank connections at the steering valve are the same thing, hydraulic tubing bent and tig welded together just above where the hose connects. All the tubes & fittings came from New-line hose & fitting (Canadian). Their catalog has pretty much every hydraulic fitting you could ever want.
I got away with a standard bolt in the front engine mount, no room for a washer though. I definitely considered a carriage bolt but I just got by without. My engine also had the right rear foot broken off of it before I got it and it had been tig welded back on. Didn't want that to happen again so now there's a 3/16" plate underneath the motor, 1/4" rubber washers between the plate and the frame, and 1/2" rubber washers between the bolt head and the bottom of the frame. Well, on 3 of the 4 mounts now that the cylinder is the way. Hopefully that's still enough!
Thanks for all the positive comments! I'm glad others like it. After running it for a month, everything is working great. I was concerned the 100cc steering valve would be fast and cause the steering to feel twitchy but it's actually perfect. Any smaller would be a lot of cranking going from lock to lock. The loader is a little slower with the priority valve stealing some flow but it's not bad. I have a slightly larger pump than the factory one in it anyways so it's probably running the way a stock one would anyways, I just got used to the speeeed.
I did also underestimate the amount of play in the front axle when I measured everything up. I think I originally said I made the ram 3.5" stroke, but it's closer to 3.25/3.38" somewhere in there. Probably should have made it 3.63". Anyways, I cut about 1/2" out of the steering arm at the axle to get a little more throw and now I have about 95% steering travel so I'm happy with that. It's actually has more steering angle now that it ever did with super sloppy manual steering.
Absolutely not
What a pain those things are to make, you couldn't pay me enoughThere are companies around that will bend them up if you bring in a sample. Talk to your local hydraulic supplier if they don't do it they can probably point you in the right direction
The drain to the machine is tee'd into the return line between the TCV and the loader valve. I just drilled a hole and tig welded a small piece of tube to it with a ORFS end. You can see the hydraulic hose in the bottom right of the video at about 23 seconds in, that is the return. The power beyond and the tank connections at the steering valve are the same thing, hydraulic tubing bent and tig welded together just above where the hose connects. All the tubes & fittings came from New-line hose & fitting (Canadian). Their catalog has pretty much every hydraulic fitting you could ever want.
I got away with a standard bolt in the front engine mount, no room for a washer though. I definitely considered a carriage bolt but I just got by without. My engine also had the right rear foot broken off of it before I got it and it had been tig welded back on. Didn't want that to happen again so now there's a 3/16" plate underneath the motor, 1/4" rubber washers between the plate and the frame, and 1/2" rubber washers between the bolt head and the bottom of the frame. Well, on 3 of the 4 mounts now that the cylinder is the way. Hopefully that's still enough!
1 - 11 of 11 Posts
