The Stovebolt Site Forums The Shop Area Driveline So, you think you're smarter than GM?

So, you think that you are smarter than a GM mechanical engineer?
Well I can tell you that I am not.
I took my '49 for a reliability test run at highway speed and noticed super sloppy steering and near death wobble over 55 MPH. Never had that problem before. I carefully drove it home. I finally crawled under it today today to see what was up.
The steering arm which connects the drag link to the tie rod is held to the steering knuckle by 4 nuts and bolts. The nuts look like castle nuts, but are actually lock nuts. The problem is, they lose their locking feature over time. GM apparently new this and drilled the ends of the bolts for cotter pins just in case they loosened up, so that you won't die in a fiery crash.
When I put these nuts and bolts on when I built this truck, I noticed that the nuts no longer had their locking feature any longer. So being "smarter" than a GM engineer, I put lock washers on and did not put cotter pins in the holes. What could go wrong with that idea?
Plenty. When I took the nuts off today, there was only one lock washer. How did that happen you ask? Lock washers are brittle and break into pieces when under too much stress, that's how.
Lucky me, (other than not dying in a fiery crash), I had two NOS lock nuts and I am back on the road, albeit humbled.
Carl

I thought about that when I was bolting together the steering box. I used aircraft grade nylock nuts with grade 8 bolts. GM didn't install a Saginaw steering gear on the My 59' so I had to improvise. I guess time will tell me if did it right.

In my experience the AD trucks used castellated nuts and cotter pins to hold steering arms on. I remember because the cotter pins are difficult to remove after half rusting away.
To know for sure the parts book might explain.

In the late 80's and into the 90's on a a GM straight axle the steering arms bolts have a heavy SAE washer and self locking all steel nuts.

52carl,

I just reassembled both steering arms on my 52’. Fortunately, I still waiting on wheel bearings so I haven't driven it yet. When I disassembled, all four bolts had lock washers. If I understand correctly, your saying that the lock washers don’t belong.

I’ve looked in the Assembly Manual and Service Manual for any diagrams to confirm this and did not find any. Do you or any of our fellow “Bolters” have any documentation showing the assembly of this connection?

Phak: I have a '54 service manual that has photos and a diagram that clearly shows the cotter pins. The photos are in the section on adjusting front brakes.

I am assuming the bolts you have, have holes in the threaded shank to put a cotter pin thru the slots, and the hole, after nut is tight.

I don't think locking nuts with "locking features" were used in 1949. The cotter IS the safety/locking feature. The only "integral locking feature" possible back then could have been "deformed threads type". In the case of castle nuts, that may mean the "castles" were bent inward. I doubt you have that. If you do, it could be a PO added nut. Which I say is a wrong nut. That kind can damage the bolt threads if the nut is harder than the bolt.

Castle nut is a word for castellated nut. Comes form the castellations on a parapet wall of a castle.
You could also have a slotted nut. Either will work.

I respectfully assert that your analysis of what you saw is mistaken. The holes are there for a cotter pin as you rightfully say, which is used with castellated nuts to lock them. In this case, you torque to minimum or mid spec, then tighten to catch a cotter pin hole. 60 degrees max rotation.

This case has nothing to do with the other use of castellated or slotted nuts and cotter pins on a spindle/wheel bearing where, in many cases, you "back off" to a hole to crate proper end play/bearing pre-load. (depending on tapered roller or ball)

Excuse my loose use of terms. These nuts are neither castle nuts, nor castellated nuts. I called them castle nuts because the end of them look like the top of a castle.
The castle portion of them are crimped slightly inward to deform the threads to make them lock. Once installed, the single hole in the end of the bolt for the cotter pin does not match up with the castle end of the nut. Too far away. Even if it would engage with the castle end of the nut, you would either have to strip the fine threads, or leave the nut loose to make the pin engage with nut. Trust me, you do not want to leave them loose.
As I mentioned earlier, I have some unused replacements which look to be NOS, and they indeed do function as lock nuts.
BTW, I did use thick flat washers under the lock nuts.

I was typing/editing while you posted. Please read all again. I will stand by my opinion and stick my neck out and say your NOS nuts are not. I don't think they are supposed to be deformed thread. Until Tim posts his parts book that says otherwise.
You DO have a castle nut by definition. There ARE locking castle nuts. I would not use them. Use the procedure I described.

Too far away? Like what do you mean? The original hardware and components stack up was determined by those engineers when they put in the hole. You have non original hardware or are missing something. You can use flat washers to catch up or a different non locking nut. This is more proof that the nut is the wrong nut. You are going to ruin the bolt threads!!!!!!!!!!!!!!! with those deformed thread nuts. They are not supposed to be reused, ever. They also shave up burrs and the next locking nut cuts the bolt more.
Peace out.

Are either/both of these illustrations helpful in this discussion?

1954 front brakes

1948-1951/1952/53 front brakes

Tim, the illustrations are exactly what mine look like. My lock washers look like the were original to the truck. They are much thicker than normal lock washers. As bartamos pointed out, the stack up (washer & nut) align the hole to the slots in the castle nut perfectly.

I guess my concern is should it be a thick flat washer or a lock washer. I an sure that there are many “bolters” out there that have disassembled this connection that could help us figure this out.

Carl's original post scared me plenty so I went out immediately last night to look at my '50 COE and '37 1/2 ton. I performed frame off restorations on both trucks, which, to the best of my knowledge had never had the front axles disassembled before. I re-assembled as I found them. Both trucks have castle nuts that hold the steering arm with thick flat washers (not lock washers) and holes in the bolts for cotter pins, The other 2 bolts that hold the backing plate to the spindle at the top are standard nuts, with the same thick flat washer, with no holes for cotter pins. I think you can see this in Tim's pictures he has linked. The castle nuts are normal thread and do not lock or deform the bolt threads.

Regardless, thank you Carl for sharing this with us as it is important issue with serious safety implications.
Kent

Yes Tim, good info. A little blurry on my computer.

Phak1: I would have thought the washers would be thick, load spreading flat washers.

Kent has sealed the deal. I would think the 2 regular nuts at top would have lock washers along with the thick flat washer.

Lock washers, self-locking nuts, cotter pins, and even safety wire are for people too timid to put the proper torque on bolts. Properly-lubricated and tightened bolts and nuts do not get loose and back off. If you use a higher grade bolt than what was used originally, be aware that any factory torque specification you find will be far too low to keep the fastener tight. A bolt has to stretch a certain percentage of its length to stay tightened properly, and if a Grade 8 bolt is used in place of a Grade 5, for instance, you MUST look up the proper torque value for the grade 8 and tighten accordingly.
Jerry

Jerry is correct about proper torque to stretch a bolt!
Lubrication and the right torque will keep the parts together.
That is straight from my Nuke training!

Don

Jerry is a respected expert and very knowledgeable member.

So before anyone gets their shorts in a wad, he is speaking about automotive. He knows about aircraft hardware, spacecraft hardware, drag and speedway racing and other industries who would require, some by government mandate, to have a locking feature in "fail safe" conditions where it is just too risky otherwise. This would include safety wire and other approved locking features. Which do not include nylon locking inserts at all and sometimes do not include deformed thread locking features on service hardware. This is where Dzus is sometimes used.

What he says about torque and stretch and grade, shows his understanding of fastener engineering.

Most of the time, on our trucks, it's best to use a split lock washer on top of a flat washer and torque to spec.

You can see that on spindle nuts, steering, suspension, and brake hardware, there are castle nut/cotter pins used. Those are our "fail safe" areas. Sometimes, as everyone knows, cotter pins are used on a clevis pin as a retention device. (shift, pedal, throttle and Ebrake linkage). You obviously can't use locking or torqueing on those movable joints.

Then there is the tab locks on exhaust manifold bolts and tranny mount bolts. OK Ok ok

Bartamos:
Electro-Mechanical Design Engineer
Honeywell Aerospace
Ret.

"Thanks for your support- - - - -!"

One thing some folks don't consider when substituting higher-grade bolts is that the nut must match the bolt. If it's going into a threaded boss in an engine block where the female thread can't be upgraded, it might not be a good idea to go with a higher-rated bolt than original, especially in the case of cylinder head or main bearing fasteners. I have substituted studs for bolts on occasion on cylinder heads subject to high compression and RPM situations, since it's possible to use much higher torque numbers when the stud isn't turning in the threads in the block as the nut on top is being torqued.
Jerry

All that I have to add to this discussing at this point is that every one of these bolts which I have removed for service on several different 3100s have had the same 7/16" fine thread bolts with the hole for the cotter pin (next to impossible to find a non stock and suitable replacement), and a thick flat washer. Once the nut was torqued down to specs, the hole in the bolt was too far out for it to engage with the gaps in the end of the nut. (If you squint, you can see this in Tim's pic.)
If the hole had been located so as to engage with one of the 6 gaps in the end of the nut, the odds of the hole ending up lining up with one of those gaps would be less than 50/50.
I would not attempt to over torque fine threads to reach the next gap, nor would I back that nut off one little bit to make a cotter pin to line up with a gap. (A moot point, given that the holes are not located so as to engage with the nuts.)
My theory on the design is that the cotter pins are there to prevent catastrophic failure should the LOCK nuts (yes, I am standing by my position that these are lock nuts) loosen up while driving.
Carl

Ok, but I want to know the brinell of your skull. ______this space for smile emoji. (on backorder)
Carl, it's me, your buddy. Would I "steer" you wrong?

I typed a response, but had to delete it.
And I had to do it again!
Right Jerry!!!

Don

Carl, that cotter pin hole is a good example of the "fail safe" concept- - - - -it doesn't keep an improperly-torqued bolt and nut from getting loose- - - -it just keeps the pieces from falling off and getting lost if there's a pin in there!
Jerry

OK, I think we can collectively agree that the lock washers don’t belong and I need to replace with thick flat washers and the castle nut doesn’t engage with the cotter pin. It’s purpose is strictly as a fail safe.

OK! Now Jerry’s point on different grade fasteners brings up another question. The bolts in question on my 52’ 1/2 ton are 1/2”-20. I made the assumption that they would be grade 8.

Are they grade 8?

Phil H

Interesting convo, lets throw a proverbial wrench into the mix, what about the hub axle nut, it's torqued to a certain value then backed off if needed to align with a cotter key hole and slot in a castle nut, seems to me it's not a fail safe but an actual locking mechanism, what-ya think?, LOL.

Per the smart engrs

Two different animals. The 33 ft. lbs. torque applied initially applied are a pre load and to insure the bearings are seated. You back off 1/12th to 1/6th of a turn to get the cotter pin to align which gives you the required clearance for the bearings. This insures that they are tight but not to tight to run smoothly. In this case the cotter pin does engage with the castle but thus preventing the nut from backing out.

The steering arm fasteners are torqued to spec. and not moved as this insures the proper stretch of the bolt. Looking closely at this joint, you will notice that the cotter pin is actually above the nut and does not engage. The cotter pin in this case is a “fail safe”, just to keep the fasteners from completely falling out.

Phil

Phil- - - -without some sort of confirmation from the engineer who specified the bolts for that application, it would be difficult to determine what grade of bolts were used. You might have to dig him up and ask. Good luck with that! Are there any identifying marks on the bolt heads? Usually a Grade 8 has six lines on the bolt head, while a Grade 5 only has three. The bolts without any ID marks that are found in bulk bins at hardware stores are usually Grade 2, and aren't really intended for automotive use. I'm sure there are a lot of them running around on stovebolts and other vehicles, however. I'd be a little reluctant to use a Grade 2 bolt in a high-stress area like a steering system, however.

Vol- - - -in the case of a spindle nut, there is a little wiggle room on bearing preload, and the cotter pin is used as a mechanical locking device. Later model spindle nuts have a sheet metal lock collar with a lot more choices for positioning, so an accurate preload can be done with an inch-pound torque wrench and the nut doesn't need to be backed off. On GM cars from the 1970's and later, I believe the torque spec. is 72 inch-pounds. That's for tapered roller bearings- - - - -on early stovebolts with ball bearings the "torque and back off" method seems to work OK.
Jerry

I find this interesting. As you can see in the picture, my bolt head has five lines with a circle and an “M” in the middle. I’ve looked for the last half hour on the internet and can’t find any place to identify the grade of this bolt . I’ve even consulted my bible, Machinery Handbook to no avail.

Anybody care to take a shot?

I know nothing about grade markings on bolt heads.

Two SAE grade markings charts are attached.

Tim, Thanks you came thru again! You wouldn't happen to have a torque table for grade 7 bolts in your back pocket! LOL

Where our debate has gone of the rails a bit, is from attempting to come at the issue from two entirely different perspectives.
1) Late '40s/early '50s GM design.
2) Everything which you have brought up.
While you have brought up some very pertinent and valuable technical information, many of them do not apply to what GM did from '47-'55.1 with the steering arm bolts/nuts.
You need to buy you an AD in original condition for 2 reasons.
1) So that you can hang out with the cool people.
2) So that you can witness firsthand the many peculiarities which you don't see on later models. I find myself asking myself, "Why'd they do it that way?" Most of the time it was due to the limited technology available at the time, and cost saving constraints.

I will say this. There are numerous peculiarities on the ADs (these steering arm bolts/nuts included) which would definitely be improved upon by many of your suggestions.
Carl

OK, here is my last try. This is NOT aimed at Carl, it is aimed at the misinformation.

1. The castle nut/cotter pin is a locking feature. Period. It is used instead of other types of hardware locking that were available back then. Namely lock washers. Because it is unlikely to loosen (or tighten). In the Aircraft world it can be called "fail safe" if compared to a lock washer, etc. Forget I ever used the word fail safe.

2. If you find a castle nut, on an old truck, that has deformed threads and a cotter pin, it's wrong.

3. If you find a castle nut, on an old truck, and the cotter pin is not down into a slot. It's WAY WRONG. You must use additional washers or a thinker washer or drill a new hole or whatever it takes to achieve a torqued lock with a cotter pin.

4. I already explained how to install the castle/cotter on torqued steering hardware we are discussing. When you torque to min-mid spec and then turn to the hole, you install a cotter pin that just kisses the nut slot. The nut can nether tighten or loosen. This "in the slot" applies to the full torque cotter pin or the backed off preload cotter pin. This is a very common and well known method. What is all the fuss about?

5. I doubt if early engineer ever heard of Gr 8 bolts. I doubt if stretch was known. A grade 5 bolt, of those sizes, is mega strong.

6. You can see for Gr 5 and up you just add 2 to the markings to get the grade. Not sure when grade marking began and you can't trust some off shore markings or PO hardware. Just use a good new Gr 5. Gr 8 is not necessary.

I give up, bartamos. You win. There has never been an instance, since the beginning of time, where anyone has been more right than what you are on this topic...

For those of you out there who actually have an AD and have actually looked at the fasteners in question, make sure to read ALL of the posts in this thread, and make your own conclusions.
Carl

There is nothing to win. I can't find any pictures or legit information on AD or the use of castle/cotter other than what I and others have seen on their legit AD's and other old trucks have posted. I have also searched the web, old repair manuals, engineering info and my knowledge.

If someone has this info, I will humbly stand corrected. If a person relies only on what they see on their AD or other, they can be wrong to assume it is "original". All kinds of yahoos have worked on it before you got it. If you copy a yahoo, you are..........

I don't want to create anything but a record. Not animosity. I have to stick to my opinions until I get proof, that's all. Some of what I see and read is disturbing.

Some discussion was mentioned regarding fine threads not being strong enough to tighten to next castle slot. Fine threads have larger tensile stress areas which in turn make them stronger in tension than coarse threads. Fine threads also possess larger minor diameters, which provide high shear strengths.

Quoting from the 55-59 TF Maintenance Manual which I doubt is different than AD. This is assembly of STEERING KNUCKLE:
"Tighten upper and lower ball stud nuts (7 and 8) to minimum torque listed in "specifications" at the end of this section; then continue to tighten each nut until slots in nut line up cotter pin hole in stud and install new cotter pin."

I can find as many examples as you wish. Only because some may think I'm strutting around on this, like I know everything and being cocky. I try to study an issue and after I'm done, I post what I find using my experience and knowledge to verify. I have been wrong a time or two. Remarks do not discourage me, facts do. Friends can disagree. Everyone feel free to assemble your parts as you wish. Feel free to interpret "locking", any way you wish. Interpret the method of locking, any way you wish. Interpret how to use a castellated nut and cotter pin any way you wish. As they always say on Stovebolt, it's your truck.