What front axle?

[Bigdogtrucker]

1968 R611T, has a Rockwell R170 rear from the factory and 10:00X22 rubber. Was wondering what front axle is would be, and would it be the same as used in a B as it looks a bit narrow?

[Rob]

Probably an FA-511, or FA-512 which were very common in that series in those years. The hubs make the axle look narrow compared to the later styles.

[Bigdogtrucker]

Yeah I was thinking the 512 I know it wasn't a 522. Do you know where the stamping is on these?

[Rob]

The 522 is under a B series and too narrow for the R. The stamping is around the right side spring saddle of the axle beam. Look from the front of the truck.

[h67st]

Should look like this.

[Bigdogtrucker]

10 hours ago, h67st said:

Should look like this.

looked around on the front of the axle couldn't find it could it be in the back possibly?

[Rob]

No. It will be stamped into the axle beam itself below or very near the spring seat and viewed from the front of the truck looking rearward. It could be a faint, or light stamping and may take a wire brush or wheel to reveal it. I have never seen an axle that was not stamped unless it was a Rockwell/Meritor, or sometimes Eaton. If any of the vendor axles, there would be, (or have been) a tag riveted to the front of the axle beam centered under the truck and viewed from the front.

I have never seen a vendored front axle beam under a eastern R model but have on a couple of westerns.

[Vladislav]

On 2/7/2021 at 4:24 PM, Bigdogtrucker said:

looked around on the front of the axle couldn't find it could it be in the back possibly?

Easily. My R-model axle beam had its stamping at the front. I type "had" because I removed it from the truck at a certain time. I investigated it through very well before sandblasting and paint and found no reason I couldn't put it backwards installing back on the truck. So you know where to look at. My understanding you will find the stamping or a ground off spot where it was.

[Rob]

Although the axle will physically bolt in backwards, I'll wager it would really be an adventure to drive. You have steering angles which would all be incorrect. Negative caster where the original was positive. Incorrect camber for both sides of the truck. Steering axis inclination really out of kilter. Many of these angles are designed and machined into the axle, and spindle forging(s). King pin inclination for instance which is 7 degrees positive in this application. This is never neutral but rather positive meaning to top of the king pin is more to the rear than the bottom. Reverse the axle beam and you reverse the angle which directly affects caster, camber, toe out on turn, etc.

Naw, really don't think your axle is installed incorrectly myself as you would know it at very low speed and find it most likely uncontrollable at normal speed.

I've seen some of those axle stampings be quite faint over the years and obscured by rust/corrosion. You can usually find them with a heavy wire brush on a small grinder after you get the axle beam down to shiny. It is always preceded by "FA" and a number. Sometimes there is a hyphen after the "FA", sometimes not and just a number unless as Vlad has mentioned, been ground off for some reason.

[Vladislav]

On 2/10/2021 at 4:06 AM, Rob said:

Although the axle will physically bolt in backwards, I'll wager it would really be an adventure to drive. You have steering angles which would all be incorrect.

Rob,

I have removed FAW537 axle from my R-model and also had FAW538 off another R-model as a spare. I had to use that spare one for the truck so investigated both of them relating king pin hole angle, straightness and even the weight. And now I can state both of those were almost similar and absolutely symmetric face to back. King pin holes were bored straight from the top of the beam having zero angle to the drive direction. Castor angle establishes by the springs hanged to the chassis rails at a certain angle and also by wedged pads put between the axle beam and springs. So I bet no difference in steering or handling the road if you put the beam backwards. That's for a R-model. A few years back I had similar experience with my military Mack model NR. Also had two similar beams and chose one of to use. I well remember I found no difference face to back excepting that marking at the front of the left spring pad and even put my own mark for the drive direction of the truck just for any reason.

[Rob]

17 hours ago, Vladislav said:

Rob,

I have removed FAW537 axle from my R-model and also had FAW538 off another R-model as a spare. I had to use that spare one for the truck so investigated both of them relating king pin hole angle, straightness and even the weight. And now I can state both of those were almost similar and absolutely symmetric face to back. King pin holes were bored straight from the top of the beam having zero angle to the drive direction. Castor angle establishes by the springs hanged to the chassis rails at a certain angle and also by wedged pads put between the axle beam and springs. So I bet no difference in steering or handling the road if you put the beam backwards. That's for a R-model. A few years back I had similar experience with my military Mack model NR. Also had two similar beams and chose one of to use. I well remember I found no difference face to back excepting that marking at the front of the left spring pad and even put my own mark for the drive direction of the truck just for any reason.

Hi Vlad;

I can't answer directly for the FA-537, or FA-538 as never have rebored either. I have rebored and installed sleeves into the FA-512, and FA-522 series in early R, and B series in the past and these borings are not perpendicular to the horizontal plane and it does seem they have a slight positive, (top more towards the rear) bored hole. What I'm saying is the top of king pin is tilted out and rearward from the bottom. Much of this follows the "Ackerman" principle of steering geometry. However, it is possible being the FA-53X series was designed more for the balance between manual, and hydraulic power steering where the FA-512 really was geared more towards the manual types in use then. I don't know.

I have rebored several Rockwell axle ends installing "Stemco" inserts to correct for "beaten" king pin bores several times. Those are usually bored with a slight positive caster angle, (top of pin to the rear) and an adjustable sleeve pressed in. Caster plates are used often for setting the final angles meaning slightly rotating the axle beam under the springs to achieve the correct angle. It gets tricky when the actual beam needs twisted to attain equal angles on both sides of the truck. Heat, and hydraulic force are your friends here. 

[Vladislav]

5 hours ago, Rob said:

I have rebored and installed sleeves into the FA-512, and FA-522 series in early R, and B series in the past and these borings are not perpendicular to the horizontal plane and it does seem they have a slight positive, (top more towards the rear) bored hole.

Sounds interesting. Originally I met an issue with my original truck's beam having one king pine boring wore out. Looked for a fix, figured that Stemco tube could be used and even found a machine shop with a mill large enough to work the axle out. But having an extra axle but of heavier rating I resolved using it if it's suitable. That way I played a couple of hours with both of them putting both horizontly and on a side and checking by laser level. Also checked the angles the king pin holes bored to the side (or better to say off the side) and found both beams were similar. Also I remember I put a bar or so into the bores centering it some way to measure the angle by the long portion of length and pretty sure there was no evidence of leaning to rear or front. It also makes sence having caster plates (all my R's and 2 MH's have them and they look stock) there's no hard reason to do machining of an axle beam more complicated. Much easier to add a grade or two to the wedge and it's done.

Edited February 13, 2021 by Vladislav

[Vladislav]

5 hours ago, Rob said:

However, it is possible being the FA-53X series was designed more for the balance between manual, and hydraulic power steering where the FA-512 really was geared more towards the manual types in use then. I don't know.

Usually power steering equipped vehicles have larger caster angle since it's easier to "fight" the tendency to go straight and manual steering rigs have just light caster. On the other hand it could be the way FA-512 were bored with a light lean but had no caster wedges and once FA-53X were used with them the reason to add the angle to the bores disappeared.

Edited February 13, 2021 by Vladislav

[Rob]

Hard to say for sure but not hard to set an angle table to a certain degree and plunge cut the bore with final reaming to size. Only seen videos of beams being manufactured but they are run in jigs and the operation is quick on the manufacturing.