Mack dual steering box relief adjustment.

[crane operator]

R series Mack with a national boom truck. Truck had rims on it with not enough offset, so it had a horrible turning radius, it does have a fairly long wheelbase that doesn't help. 425 floats up front.

I've installed new front rims with much more offset, and adjusted the axle stops in, so now I have at least some turn.

The problem is that it seems to stop turning at the old axle stop location. If I jack up the front end, it will go from stop to stop. If I'm sitting on the tires, with the weight of the crane on them, it only steers to the "old" angle area, and runs out of power steering. If I'm rolling, I can force it to turn to the axle stops, but it takes a pretty good pull on the wheel.

I'm thinking the pressure reliefs need to be reset in the steering gearboxes. I've never done this, so I'm kind of flying blind, but willing to listen to any old Mack man's advice.

The only other thing that might be happening, is the king pins "rough" or dried up where the "old" setting stopped, making it hard to turn, but I don't think that's the case. I gave them a good greasing, and you can disconnect the pitman arms and push them around.

The Mack has dual steering boxes, and they are the inside the rail style boxes, so access isn't great.

Couple pictures.

I'm assuming the pressure relief pins have to be in each end cap, so that the piston would move each way and "release" the pressure? but it doesn't look like these boxes have any adjuster pins in the end caps.

 

[Truck Shop]

Those look like Shepard steering gears. Personally I would get the Mack info for adjusting the internal stops. I had some International 1954's with the same set-up
some years back and I had Int fax me the procedure and glad I did. If those were TRW {TAS} steering gears it is simple to reset.

Truck Shop

 

[crane operator]

Thanks Truck shop. I found a shepard manual, looks like only the master will have stops/ adjustable pressure reliefs, not the slave. The master reliefs take the pressure off the slave also. I guess I'll have to pull off that bracket and look for the plunger. Should be under the bracket for the steering shaft and on the bottom. Thanks.

 

[kshansen]

Only ever really worked on single steering box Macks but hose are Shepards that look identical to the single box designs.

The "master" should have adjusters located where the red circle is in the picture below. It is a simple pin that off seats a little ball check valve thing on the piston inside the box. Back out to get more turning and screw in to limit the turning. Probably a more exact description in the Shepard manual!

 

[crane operator]

Bad news. The adjusters are on the master, top and bottom, right where the castings are on the slave, but someone has messed with the top one before, and the flat head screw is stripped. The bottom one moved out, but the turning radius didn't change, so I wonder if that ball is stuck in the seat. Either way with the flat head stripped on the top, its got to come out and get fixed. One step forward and two back.

There's a outfit in texas that rebuilt my last steering box, this one will probably go to them.

 

[crane operator]

Steering box came back from Texas last week. Got it installed and the adjusters working. Truck goes easily from stop to stop, (I set them up to stop the power steering 1/8" or so from the stops). Light pressure on the wheel, will easily turn the front end. Thanks for the help guys.

 

[DMiller]

Sheppards are not hard boxes to work on, dealt with them on IH and A-car chassis, mostly heavy steer as dump trucks or mixers. Actually dependable gearboxes, but watch the pitman arms, that one should have the allen retainer set screws and they were notorious for loosening on their own once they were loosened the first time.

 

[kshansen]

We had lots of Sheppards on the Mack at the quarry.

The biggest problem we had with them was leaking out the input shaft seal. I see Crane Operator's box has the grease fitting to lube the input shaft many of our older trucks did not have that and with the dirt and wet that built up on them they would get rusty and pitted on the shaft.

Some we could fix with a Speedi-Sleeve and others we had a shop near here that couild build them up and grind back to standard. Last resort was to replace with new as we knew the problem would be back!