Halfshaft Bolt Answers (all threads merged)

[analogdesigner]

12 pt. fastener fit...

Jay,

Even the smallest 12-pt ARP fastener heads will not fit side by side because the bolt centerlines are too close together. FYI.

Kendall,

I was afraid of this, however, I was going to investigate the possiblity of turning washer portion of head down to size. What do you think? I ordered the 30 mm long 12 point fasteners. They are not threaded up to head. I can shorten them by 5 mm if necessary. I may have to a thin walled socket to install these.

Thanks for the info and as always I will keep everyone informed.

Happy Super Bowl,

Jay

 

[analogdesigner]

Worse case thermal differences

Gimbal and Shadowman, is it possible that the tollerances reduce when the transaxle gets up to operating temperature? I know that good designs provide for expansion og the metals at operating temp.

dbtgt, (sorry to butt-in guys)

This is always an engineering consideration, since the heat usually originates from the transaxle. I suppose that there could be as much as 100 degrees C difference between the axle and the coupler. Perhaps if the engine/trans was very hot and then something cold (ice or water) gets on the coupler. The clearance across the diameter would reduce roughly 0.0015 inch, or about "1.5 thou".

Jay

 

[Gimbal]

Kendall,

I was afraid of this, however, I was going to investigate the possiblity of turning washer portion of head down to size. What do you think? I ordered the 30 mm long 12 point fasteners. They are not threaded up to head. I can shorten them by 5 mm if necessary. I may have to a thin walled socket to install these.

Thanks for the info and as always I will keep everyone informed.

Happy Super Bowl,

Jay

Jay, I measured the thread depth in the axle and 30mm long bolts are just a bit too long, so I trimmed them to 25mm. I had to buy 30mm since the 25mm were fully threaded and the 30mm had a nice radius at the bolt head. I also drilled for saftey wire. They were cap screws, 12.9 strength.

I found some 12pt, not fully threaded but they are not fully threaded enough, so I could not use them.

 

[analogdesigner]

Jay, I measured the thread depth in the axle and 30mm long bolts are just a bit too long, so I trimmed them to 25mm. I had to buy 30mm since the 25mm were fully threaded and the 30mm had a nice radius at the bolt head. I also drilled for saftey wire. They were cap screws, 12.9 strength.

I found some 12pt, not fully threaded but they are not fully threaded enough, so I could not use them.

Gimbal,

Thanks for the update. Yes, I was also concerned about the thread length. I had considered using a thick, precision NAS style hardened washer under the head of the fasteners if necessary.

Just curious, did you use anything for thread lube prior to torquing? What torque value did you use?

Thanks again,

Jay

 

[dbtgt]

Gimbal,

Thanks for the update. Yes, I was also concerned about the thread length. I had considered using a thick, precision NAS style hardened washer under the head of the fasteners if necessary.

Just curious, did you use anything for thread lube prior to torquing? What torque value did you use?

Thanks again,

Jay

Jay, excuse me for butting in - but Ford is recommending we loctite these bolts so that would in fact be the thread lube wouldn't it?

 

[Gimbal]

Gimbal,

Thanks for the update. Yes, I was also concerned about the thread length. I had considered using a thick, precision NAS style hardened washer under the head of the fasteners if necessary.

Just curious, did you use anything for thread lube prior to torquing? What torque value did you use?

Thanks again,

Jay

Hi Jay,

I used blue loctite, this acts as a lube during torque, you need to hurry before it cures though. Loctite cures due to an absense of air.

I torqued the 2 bolts just under the spec in the TSB, about 2 Ft-Lbs less. I thought it would be tight enough and maybe, just maybe allow for a bit more load or what ever to the bolts before they break. I guess now I am waiting for either the bolts to break or Ford or someone else to come out with a real fix.

 

[nota4re]

I was going to investigate the possiblity of turning washer portion of head down to size. What do you think?

Jay,

As you have pointed out previously, I think there's a big difference as to solutions I might try on my own car and ones that I could advocate to others. My opinion is that ARP has a very specific hardening process and I would would worry that turning any material off of the bolt may adversely effect the bolt (head) strength.

I assume that you may have ordered the ARP Stainless 300 fasteners. If so, they have a tensile strength of 170,000 psi whereas the factory bolts are a grade 12.9 with a tensile strength of 177,000 psi. Let's call it a push.

Further, the bolts you ordered may have shoulder that is too long for the applicaton we seek.

Here's a few pictures that may shed some more light on the topic...

From the top, there's an ARP M8 12pt head 30mm bolt, an ARP M8 12pt head 25mm bolt, and a factory M8 12.9 Allen bolt.

Here's a picture of the head to head interference of the two M8 bolts in the updated Ford hardened washer.

This is a picture of the shoulder length of the 30mm ARP bolt being too long.

Regarding the new hardened washer, you can clearly see the relief (chamfer) on each of the bolt holes.

Finally, here is a close-up (not quite focused) of the factory M8 Grade 12.9 Allen bolt. You can see a shoulder and small radius up to the heads. Not bad.

While both the bolt strength and the spline mesh may be contributing factors - neither is the curent focus of what we're currently looking at as the "primary" design issue. I hope to have more information soon.

 

[analogdesigner]

Kendall, nice work!

Kendall,

Many thanks for the time you spent documenting, photographing and posting everything. :thumbsup

I had spoke with a friend of mine that had already drawn that particular fastener in Solidworks (3-D solid modeling program). The interference that I had expected is just as you show it. Fortunately, the ARP 300 alloy is very similar to 17-4 ph stainless. It's acceptable to machine any amount from the outside of the integral head/washer, since the material properties will not be affected. This is not a heat treatable alloy, so this is why we can get away with doing this. Also, there is virtually zero stress at the outside edge of the washer. The integral washer in the 12 pt. fastener will be far more vibration resistant and fatigue resistant than a socket head fastener. This is due to the increased surface area compared to the socket head fastener. This is probably good news for all of us!

I will carefully calculate the proper torque value, because on a car with a "good" spline fit, the fastener should be torqued to >75% of it's yield strength. Note: this is much higher than Ford recommends...

I will measure the length of these before I install them. Later on, I will remove them and re-measure them to ensure that the yield strength has not been exceeded.

One other thing, there should be 1.5 turns of exposed thread from the region where the thread within the axle ends. This is an aircraft standard. This means that your 30 mm, 12 pt. fasteners may be perfect!

One more thing, what brand of camera are you using?

Thanks again for your help,

Jay

 

[Gimbal]

nota4re,

Can you give us a hint what you think the real problem might be?

Thanks,
John

 

[dbk]

A single digit number of cars have had a double failure. Of those, all but two were a case where a different side broke each time, which makes it pretty clear that the fix (i.e both sides!) wasn't properly done. The other two, it's not clear, but I'd make no assumptions on what happened yet.

Either way, the topic is now being actively addressed and we should have communication soon.

I personally know one car where the failure occurred at just over 1k miles, but that car now has over 20,000 hard miles since and the fix-bolts checked out fine upon inspection...

 

[BlackICE]

Either way, the topic is now being actively addressed and we should have communication soon...

DBK, thanks for your efforts and the update on this problem. I look forward to the official word from Ford on this issue.

 

[Gimbal]

Can someone summarize who is who in this forum for me and maybe others? Seems DBK and nota4re seem to be some sort of real "players" and associated with Ford somehow, etc? I'm mostly interested in the axle fix issues.
Thanks a lot,
John

 

[dbk]

Can someone summarize who is who in this forum for me and maybe others?

I started and run this website, and because of the site I've got a number of friends at Ford. All I can say is that the information regarding which owners on the sites cars had the issue was collected and forwarded to the appropriate parties last week. I talked to some people last week and communication of the issue and concerns has been established.

 

[B O N Y]

Can someone summarize who is who in this forum for me and maybe others? Seems DBK and nota4re seem to be some sort of real "players" and associated with Ford somehow, etc? I'm mostly interested in the axle fix issues.
Thanks a lot,
John

Very fair question:-

Ford:- (1) They have issued a bulletin if a failure occurs the bolts and washers will be replaced.
(2) Mgmt has been recently been made aware of the failures reported by forum members. As DBK has stated we await comments from Ford.


Nota4re & analog designer (aka as Kendall & Jay):- both GT owners who have developed bits and pieces to improve the GT and have engineering backgrounds. They are independently studying the issues, drawing their own conclusions and sharing them on this forum.

ACCUFAB & THE GT GUYS: Independent sellers and installers of assorted products that have for resale kits to replace the suspect washers and bolts.

 

[Fast Freddy]

OK, looking at the picture, another idea. Don't know if this would work since I have not seen the other components all at once - that picture is one I took at the rally.

What if the was a "cap" over the whole works that would bolt to the two allen screws, and carry over all the way out so that it would have a lip that would be between the half-shaft and the transaxle - would have six bolt holes in it so that when the pieces were assembled it would not only have the allen bolts but also the compression between the pieces with an added six bolts to hold it.

As I think about this as I write, I guess it still doesn't stop the problem of the bolts loosening, but it starts me thinking outside the box (or the shaft in this case). Anyone have a schematic of the axle area of the transaxle?

A second idea came to mind as I was writing. What about notches in the allen bolts heads where a tab under the head could be bent up to "lock" it in place. Some type of butterfly washer?

What about something on the inside of the half shaft that would fit into the allen heads to keep them from turning?

I'm on a roll - don't know if any would work, but .......

Next.


Still thinking - what if the first "cap" idea had the pieces to hold the allen heads in place - then that piece is secured by the six half shaft bolts.

something could be designed like the stage 8 locking bolts that i use on my headers. check out this site and let me know if something like this would help? www.stage8.com i think that something like this could be utilzed in a way so as to stop the bolts from loosening up.

 

[Gimbal]

Thanks DBK and Bony for the info and for your help in finding a resolution with the axle issue.
John

 

[AZGT]

I started and run this website, and because of the site I've got a number of friends at Ford. All I can say is that the information regarding which owners on the sites cars had the issue was collected and forwarded to the appropriate parties last week. I talked to some people last week and communication of the issue and concerns has been established.

So I guess this makes you DBP (DearBorne Player)? :thumbsup

 

[SYCO GT]

DearBornKing

 

[Gimbal]

For those who noticed a camera system suspended above the football players during the Super Bowl yesterday, I designed and built it.

 

[analogdesigner]

For those who noticed a camera system suspended above the football players during the Super Bowl yesterday, I designed and built it.

Do you work for Grass Valley Group?

Jay