Ford 6600 power steering replacement

OzRinger

Member
The power steering box on our Ford 6600 has failed. Pulling it apart, it is a god awful design with all the thrust from the steering ram being put on a small manufactured ball bearing where the inner race is part of the recirculating ball worm/metering unit shaft, thus if it fails the worm end play moves up to the point the metering unit no longer works and it wrecks the inner race that is part of the shaft. Ours also has a badly scored bore for the steering ram.

I have been told the worm shaft is not available, a whole replacement aftermarket steering box is two and a half thousand and not rated for tractors with a loader fitted. (My location is AU not US)

So was thinking of fitting an orbital steering valve and hydraulic ram. Has anyone done anything like this before?
 
The only time that bearing should see maximum thrust is when the system is run out of oil and emergency steering is needed. That box was never designed to be steered "manually".

There are still a lot of those boxes in use today, nearly 50 years after it was designed, working just fine.
 
I had a 4600 fail on me and it too was a mess inside. Bought a new gearbox from the Ford-NH dealer for $2k.......ouch.
 
Thanks. Have looked at the 6610 type and looks like up to 1985 they used the same power steering system as the 6600.

From 1985 they moved to an 120cc orbital metering unit and a steering ram around the front axle area. I have been doing some calculations and the original power steering unit has a stroke of 3.5 inches and a bore of 3.5 inches, with 6 turns lock to lock.. Which at 1100psi pump pressure is about 10500 lbs of force. At the external steering arm this is reduced to around 3000lbs of force.

Thinking of something like a Char Lynn steering unit of 6 or 7 cu in capacity and a 2.5" bore ram to replace the link from the power steering unit to the pitman arm inside that big casting in the front.

There is a unit made in Oregon that does this. https://www.farmlandtractor.com/Power-Steering-Conv-Kit-p/fd6600psk.htm

I can not put too much force on the steering as I know that front casting is weak as we have already broken the steering pivot there once. Would prefer to keep it similar to original. I have substantial metal fabrication tools available so doing the work is possible, just needs to be engineered correctly.
 
Well an update.

I have finally built a power steering system based on a ram and an orbital steering valve.

Lot of work as I built it all from raw materials. But it works a treat and it is very similar to the original, with about five and a half turns lock to lock. The ram I made has a 2.5" bore with a 1: rod. The steering unit is not a Char Lynn but an Italian made copy 5.86 cu in/rev.

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That looks good.
How about some more info on how you built the column base and and the cylinder.
I have a 5000 I'd like to convert.
I have a 6610 with hydrostatic steering but a complete axle and bolster swap from a 6610 to my 5000 would get pricey.
I swapped a 3930 hydrostatic steering onto my 4000 a couple years ago but I had a junk 3930 to start with.
 
Probably not a lot of info. I really only copied the version I saw available that is made in Oregon.

The cylinder was pretty straight forward. To keep it compact the piston is screwed onto the rod and a scotch key used to keep it intact. A simple three piece piston seal which incorporates guide rings was used. The head gland uses common a common u cup and wiper. I make a bolt on plate on the front of the gland simply for the sake of making servicing the ram easier. You unbolt it and the U cup and wiper are easily replaced. I think I made the ram stroke 215mm. The wheels do not quite hit the stops on full lock.

The rod is threaded 7/8 UNF and the old connecting rod was cut and tapped for the rod to screw into it, with a locknut there as well. The other end of the ram was threaded (1"X16 an oddball thread) to take the same tie rod end as used on the tractor front pitman arm.

The housing for the steering unit was a 10mm base plate with a 100mm RHS with the side cut out for the metering unit to be easily fitted to. It had a machined 30 degree angle on the end and a adapter plate on top for the metering unit to bolt to. I made up the 16/32 12 tooth spline to fit the metering unit, and tack welded and pinned it onto the old steering shaft. There is a short adapter with a seal on top and plain bearing inside that goes between the top of the metering unit housing and the original steering column.

Hoses just used 9/16 JIC fittings all around.
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