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fuzzy buzzard

Dragging Wagon front axle

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Last night I stumbled on to a thread on B model king pins. H67 had a post about a set of pins he had which measured same as mine. My front axle is FA505, his is FA511. Both are rated as 8000 lbs. Does anybody know what  difference is between these axles? 

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My books show the FA511 as used under R600. R685   R685ST and R 686ST and a slightly different shape. Maybe some one swapped it in ?

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Looking at the front of truck / axle pass. side where axle goes up to spring and where u-bolts come down, there is a wide web and front axle number is stamped in there.

1QHA 

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What are you wanting to know as far as differences? Width, caster/camber angles, SAI, usage? Let me know as I have all that information. The FA-511 was used in more than the early R series.

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Rob,

The FA511 was in an H67 that Carl owns. He had found a king pin set which he did not use. We compared dimensions on king pin and bottom plug. They all matched up with my FA505 axle. 20 years ago I put king pins in my axle BUT could not find thrust bearings and I have always felt this was causing a lot of my crazy steering problems. Carl's pin set had thrust bearing and since bottom plug and pin dimensions match, I am hoping thrust bearing are same. Will find out in morning - the old draggin' wagon comes apart in morning. Will update tomorrow night.  

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34 minutes ago, fuzzy buzzard said:

Rob,

The FA511 was in an H67 that Carl owns. He had found a king pin set which he did not use. We compared dimensions on king pin and bottom plug. They all matched up with my FA505 axle. 20 years ago I put king pins in my axle BUT could not find thrust bearings and I have always felt this was causing a lot of my crazy steering problems. Carl's pin set had thrust bearing and since bottom plug and pin dimensions match, I am hoping thrust bearing are same. Will find out in morning - the old draggin' wagon comes apart in morning. Will update tomorrow night.  

Pretty sure I have a set of roller thrust bearings for an FA-505 at the shop. Both the FA-511, and FA-505 used the same king pin set if close in the same year of manufacture. The main differences were either needle bearings, ream to fit bushings, or presized bushings. Both axles are of the "Type III" design.

I've never seen a king pin set not supplied with new roller thrust bearings myself.

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Interesting - I kinda thought the orginal thrust bearings where rollers. Bearings in this pin set are ball. Reason there were no bearings in first set installed - my parts man had to order all the components separately as Mack no longer had the set complete.  

 

 

 

 

 

 

-

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The thrust bearings have always been rollers. The upper king pin stem could use needle, or bronze bushings.

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Guess my memory ain't so good after all. Got thrust bearings out today and they were ball bearings. And they were not too awful bad. The Moog Kit 8482B is the correct kit for this axle. So I don't really expect a large improvement in steering quality but I got fresh packed wheels bearing

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Describe in a bit of detail these steering problems you are speaking of.

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I have to constantly chase the steering out on the road. Get on a skinny 2 lane and I got my hands full. New king pins, tie rod ends, drag link tight, second set of new radial tires; then added Sheppard p/s (model 49) and problem is amplified because the Sheppard box is so slow and too easy to turn. There is almost no free play in box, truck been to front end shop twice. Got to reading R model front axle book - R with manual steer 1 1/2 - 3 degrees castor and R with Sheppard 4-6 degrees castor. I added 3 degrees and seemed to help (couldn't add any more, it was pulling center bolt out too far). Then replaced spacer between axle and spring with one that I machined 5 degrees into it. This seemed to help a little more. I could add 2-3 degrees more. I am slowly sneaking up on the cure - hard to check out seat covers when it won't stay  where I put it (the truck that is!). Any suggestions - I'm all ears

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need to ensure the rubber isolators in the spring perches at the front of the truck are there and holding the spring ends stable. This is a very often overlooked item. Get a pry and work the axle with both weight on, and weight off the front wheels looking for movement. Spring pins in their mounts at the rear is another place to look closely. The rear spring eyes have bronze bushings in them and they could be worn out. I've seen these spring pins worn elliptical in the housing and any movement in these area really makes for erratic steering habits.

Typically positive caster is introduced to assist in return to center at the completion of a turn and to the help the wheels steer to centerline. Steering axis inclination has a lot to do with this also but is built into the steering geometry and normally not adjustable. Increasing caster angles tends to increase steering effort required and is a bit harder on parts, (king pins/bearings) due to the increase from pin rotation centerline. Caster angles should be even but slightly more positive on the rt. side tends to correct for road crown. Can be perceptible to the driver but most times not with hydraulic power assist. Sheppard steering is always "mushy" feeling in comparison to Vickers/Ross, (IMO) although just as good or bad dependent upon your perception.

Where is toe set at?

Edited by Rob

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A good truck mechanic, who has since passed away, told me one time that if everything is tight in the front, take a look for worn rear suspension pieces.  The rear end can give some "steer" to a vehicle.  

When radial tires came along, it seemed like a little less toe in worked better than the original bias tire toe in specifications.

 

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I would suggest you not start chasing your tail moving to another area till one area is proven sound. Far too many variables still remained unsolved for to interject another area of concern. 

The mechanic was/is very correct with analogy and the same path I would pursue.

 

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Toe was set by alignment shop last trip. Lord only knows what it was set at, - there is a different crew in there every time I stop in with other trucks. Number one son spent number of years with Thomas Bus dealership, always bunch of steering recalls. He built set of trammel points for toe so my next move is get on smooth level surface (which ain't anywhere on Ignorant Ridge) and set toe.

May different ideas on toe-in with radial tires. I'm inclined to set at zero unless someone here changes my mind so let's hear your ideas !!

Thanks,

FuzzyBuzzard said that    5-5-2-2 (that's a WV 10-4)  

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You will need some toe in or return to center will suffer. 1/8" is usually adequate but setting it without turntables is a best guess scenario. 

Chasing the steering wheel is usually loose parts and your pins/bushings are really suspect in the leaf springs of everything else is proven tight. 

Have you checked over center torque of the steering gear? One of the most overlooked sources of erratic steering there is. 

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In Australia before the days of luxurious power steering and the like trucks had either a lesser or greater castor angle which caused you to chase the wheel at speed down the high

Often this is referred to as taching, like sailing a yacht

This is easily correct by returning the caster to the correct angle with wedges between the axle and the springs

The purpose of the incorrect castor angle was it made it much easier to steer at low speed as in parking ot tight manoeuvring 

Im guessing this was a common practice back in tbe day across the world

Im also guessing the castor angle was  decreased but a proper wheel alignment place should be able to give you correct castor or no doubt google can help

Then off to your local hardware store and buy a spirit level doodah that can measure angles and see what you come up with

 

Paul 

 

received-196972168319845.jpg

Edited by mrsmackpaul
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Steer axle update - remember I made new spacers to go between front axle and springs. They were made with 5 degree taper between top and bottom. This modification seemed to help steering a bunch as I didn't have to chase it so much. Today me and son sat down with trammel points to check toe-in. Turns out it was toed in 3/8", a might too much. We set it 0-1/16" toed in. Man what a difference this made - I can look out the side window now - I'll be taking pictures just like Other Dog does! Twenty years of chasing this old thing and it just needed more caster and good alignment. Think I might put 2 degrees more in it sometime just to see how it acts. But for now, the next hot topic is installing A/C. I have a new Red Dot Back Wall Unit to set between the seats. Thinking about putting condenser under bunk like Freightrain. Hoping to get ice cubes spewing out on 95 degree days.  

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That is why I wanted to know your settings before going very far. Very easy to overlook the trees in the forest when chasing one's tail. Back that caster angle down to about 3 degrees positive and you will be real happy. Too much positive caster will be hard on the king pins over time. 1/8" toe in is about as much as needed or wanted to not see "cupping" of the outer edge, and "feathering" of the inner edge of the steer tires from pavement skid.

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Fuzzy, glad you are gaining on it.  Here are the alignment specs out of a B maintenance book from back in the bias ply tire days.

Mack B Alignment Specs.jpg

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