.My '99 F-350 is a real rust buggy. I've got some projects to do then I'm going to sell it as a parts truck because the frame is so rusty. A shame really as the 7.3 purrs, the transmission seems to be a rebuilt and the truck as a whole runs great. One thing I need to fix is the steering gear. It is shot. I tried pulling one bolt out to have a piece to fit replacements. However, the tin worms were busy and it snapped right off. The shaft is 45-50% eroded away from rust.

What is the size of the bolts these trucks use? Length and thread pitch? I'm pretty sure the rebuilding company will get to take the broken bolts out.

 

Of the three bolts, I managed to get one out intact. The rebuilders got the other two. If anybody needs to know the size, they are 7/16 x 14 thread by 5 inches long. I got three grade 5 bolts in that size for temporary use until I can get some grade 8 bolts.

 

Hmm. Those bolts should be metric and have a smaller diameter in the center than at the ends.

 

I've noticed a mix of metric and SAE fasteners. I made sure to use my thread checker to check the bolt threads. The bolts wouldn't go in the metric but threaded right into the SAE. Possibly the build date makes a difference. My box is 32 spline and that is 2/99 and earlier while 3/99 and later was 36 spline pinion shaft. The new bolts go right into the ne steering gear box.

I just ant to get the truck going to get some jobs done. Once I get done, it'll go up for sale as a parts truck. It runs great. Drives pretty good and the body is rough, but fixable. The frame is a rust buggy and at the end of its service life.

 

That's odd. I just changed the steering gear in my own truck last week and the bolts were metric. Mine is also an early build, 32 spline. Otherwise, I can't think of any fastener on a 99-up SD I've worked on that was SAE.

 

IIRC, Ford used the same steering gear box bolts for many years, from the OBS trucks well into the SD era. They should still be available at your local dealer. I just measured a set of old ones removed from my ‘96, they are indeed sae standard. 7/16 x 14, almost 5.5” long. Dealer can confirm for you.


Another thread discussion regarding the matter. I’d use the proper bolts. I would not use G5, even temporary other than for fitting purposes.
https://www.ford-trucks.com/forums/1...lts-broke.html


PN: 392009-S100

 

I got some metric bolts to check and they won't fit. M12 is slightly too large and M10 is too small. I ran a tap through the threads to clean them up as some finish material was in the threads. With clean threads the 7/16 spun right through by hand. The steering gear went right in, then came out and went back in as I had forgot to put the pitman arm on it and couldn't fit it while in the truck.

The grade 5 is to hold it in place until I can source new bolts. I wanted to beat Helene. The first out riding storms rolled through about an hour after I got done. I've got a lot of other things to clean up. This poor truck has NOT been treated well. I hope it will let me do my projects before I sell it as a parts truck.

 

Jeff, I'm just requoting your post to highlight a few things.

1. Thank you. Seriously.

Merely "liking" your post does not do your pictures worth a thousand words justice. You took the time to lay out the parts bag, with the part number clearly visible, lay out the new bolts in opposing directions, lay out the old bolts, next to a measuring device, show that you had access to a 7/16-14 nut that you could test thread the old original bolts into in order to verify thread engagement on the bench...

I mean what did you not do? Bust out an electron microscope to show us the granular structure of the material, and pitch angle of the threads? You went above and beyond the call of duty to help this community know, with visual confidence, the correct bolts for the steering gear box for the relevant year Super Duty. And your post will be a reference for years to come. Thank you for taking the time and trouble to do it for us.


2. Another confirming clue, albeit arcane.

The Ford Standard Parts and Hardware Catalog number 392009 is consistent with SAE fractional bolt sizes. An M12 -1.75 bolt of a similar length, strength, and coating would typically begin with the letter N, and then some numbers.


3. Ripley's Believe it or Not..

These same bolts were used in a Ford Explorer, and while we are at it, the CII power steering pump that feeds this puppy is technically rated for only 8,500 GVWR. No surprise that the aftermarket thrives producing alternative hydraulic steering assist systems, to purportedly "beefed up" red heads and blue head steering gears, to folks upgrading to 2005+ steering gears, and drilling out the frame to install the larger bolts that fit to them.


4. The Rest of the Story Part Number

The S100 suffix stands for a special coating, as as your photo shows, indeed these Genuine Ford bolts not only have the passivated zinc, but they also have the red high strength thread locked baked onto the threads, ready for single use service. Once these bolts are removed again, they technically should be replaced with new ones. This isn't said for the benefit of the OP, who eventually plans to part out his abused truck. It is said for any future reader searching for best practices in locating, sizing, and replacing the steering gear bolts properly.


5. Don't Get Shanked When Buying Steering Gear Bolts

No, I'm not talking about getting shanked by the high price and profit reeled in by the Ford dealer from what they charged for these darn bolts, which they sell 4 to a bag when only 3 are required.

Rather, I'm talking about the bolt shank itself. Notice that bolt shoulder, the part of the bolt nearest the flange head, is full diameter, whereas the bulk of the bolt shank is of a reduced diameter, about as skinny as the root diameter in the thread zone.

A bolt that has a full diameter shoulder, and a reduced diameter at the shank, is called a stretch bolt, or a tension bolt. The reduced diameter enables the bolt to s t r e t c h a bit more than if the entire bolt shank were full diameter. The stretching of the bolt increases tension, and the raised tension of the bolt shank increases friction under the flange head surfaces, as well as at the threads engaged.

This is the type of bolt where torque to specification is important, similar to torque to yield, and another reason why the bolts should be replaced when the steering gear is replaced. The torque spec still allows for margin between yield strength and tensile strength, but clearly, with this bolt, Ford is banking on the extra tension that a necked down shank can provide.

Thus, even hardware store bought Grade 8 bolts, that are full shank diameter (and are usually imported, so who knows what strength they actually might be) do not meet the design specifications that Ford demonstrates for this application.

For those who stumble across this thread who intend to keep their truck, the $80 bucks for a bag of 4 OEM stretch bolts with anti corrosion and thread lock built in from Ford does seem like a $50 penalty paid over and above the $30 bucks to score 3 yellow zinc Grade 8 bolts from Ace Hardware... but when comparing that $50 to the cost of a steering gear fastening failure, the value equation may flip the other way.

YMMMV - Your mind and mileage may vary.


6. Saving The Best Clue for Last

It is not by accident that the final clue is listed as point #6, even though it really should be the first clue listed, but then it wouldn't be as memorable. Not just because it is the last thing read, but because it is clue # 6, and there are 6 radially oriented dashes arranged in even, clock face like opposition on the heads of the OEM stock steering bolts. These 6 dashes can be seen with the steering gear in place, without removing a single bolt. Fractional SAE Grade 8 bolts are identified by 6 radial dashes.

If the steering gear bolts were metric, instead of dashes, there would be numbers, like 8.8, 9.8, 10.9, 12.9... which are denoted as "Property Class" instead of "Grade". The numerology of metric Property Class does not match up number to number with SAE fractional sized bolt Grades. So Property Class 8.8 is NOT equivalent to Grade 8. Instead, Property Class 10.9 is the strength equivalent to Grade 8.

So instead of 6 radially oriented dashes, the steering gear bolts would say 10.9, if they were metric. But the OEM bolts for the genre of truck in discussion do not say that. The OEM production steering gear bolts on my 2000, which is way newer than "Early 99", and which have never been changed, or even loosened, show 6 dashes. That tells me, before taking anything apart, that the thread pitch and bolt size is fractional SAE, not metric.

BTW... the thread pitch of M12-1.75 metric threads (1.75 mm between each thread crown) is fairly close to 7/16-14 threads (14 threads per inch). We can easily do the math to prove this, by taking one inch, converting it to mm (25.4 mm) and dividing that by the metric pitch (1.75) which results in 14.51, which is fairly close to 14, but still not interchangeable.

 

I think I just figured out my confusion on this. I was sure I used a 15mm socket to R&R my steering gear. I just went and checked. It was 16mm, or for all intents and purposes, 5/8". So, it makes sense that it can certainly be an SAE thread.

 

I think I speak for everyone on this forum as well as mechanics all over the world when I say "Metric or SAE, I don't care. However, PICK ONE!" I'm tired of having t have two sets of tools.