Rear Axle Nut Inspection Recommendation
- Thread starter Indy GT
- Start date
Jeff, be happy to!
Although I am not lugging the 3/4 drive torque wrench, extension and 1 3/8" socket with me out to California.
Sounds like you need to make another road trip to the Midwest!:thumbsup
Although I am not lugging the 3/4 drive torque wrench, extension and 1 3/8" socket with me out to California.
Sounds like you need to make another road trip to the Midwest!:thumbsup
PL510*Jeff
Well-known member
A couple of days earlier with this post and I would have routed through Indy.
Bill I've got a lift, a 1" drive, with 3/4 adapter for the socket.
You could stop here in Seattle on your way to Sonoma. Advise eta.
p.s. Bring the extension too.
Howard
GT Owner
You guys are such a pain. You raised my level of paranoia, so I pulled both rear wheels to check the paint marks. Both were ok (2006; 10,000 miles). While I was in there I confirmed that the socket for the oil filter can (36mm) fits the suspect wheel nut.
Howard
Howard
Last edited:
Bill -
I guess I don't understand the issue of concern regarding the torque level on these nuts. Looking at the design, it would seem that the only thing that they do is hold the half-shaft to the rotor, which are both splined to transmit the power to the rotor and thus the wheel by way of the lug nuts.
It doesn't really have anything to do with holding the rotor to the hub assembly, does it? The front rotors are identical, the only thing missing is a shaft in the empty spline.
While I will agree that one should always check them whenever a rear wheel is pulled (or the cap on the standard wheels), I don't see it as an issue to get particularly worried about. Am I missing something?
Ralphie
I guess I don't understand the issue of concern regarding the torque level on these nuts. Looking at the design, it would seem that the only thing that they do is hold the half-shaft to the rotor, which are both splined to transmit the power to the rotor and thus the wheel by way of the lug nuts.
It doesn't really have anything to do with holding the rotor to the hub assembly, does it? The front rotors are identical, the only thing missing is a shaft in the empty spline.
While I will agree that one should always check them whenever a rear wheel is pulled (or the cap on the standard wheels), I don't see it as an issue to get particularly worried about. Am I missing something?
Ralphie
Xcentric
GT Owner
fjpikul
GT Owner
Sinovac
GT Owner
BlackICE
GT Owner
Sinovac
GT Owner
Yes, but never in public and certainly not in front of lawyers.
"I thought you counted all the sponges."
BlackICE
GT Owner
Ralphie,
I have not seen a cross section of the rear hub, but perhaps your comments are correct.
Understand, the classification of this nut torque as a "critical" feaure is not mine but that of FOMOCO on the FGT Wixom build sheet (Station #W10). Was it there just to "scare" assembly personnel to really make sure you torque this nut correctly? Unlikely in my estimation. The build sheets are peppered with critial torque callouts. The assembly line person had to enter in the build book the actual rear axle nut values to which the nut was torqued.
I am always reluctant to think I know more about the design than the engineers who actually produced the design.
Let's discuss this further with Mr. Alman next week at the rally. He should have a pretty good idea the consequences of torque relaxation on this stubshaft nut.
Oh, and Frank this is what is called a "technical discussion", or possibly peer review, not viewed by those in the engineering community as a questioning or challenging of one's opinion.:biggrin
I have not seen a cross section of the rear hub, but perhaps your comments are correct.
Understand, the classification of this nut torque as a "critical" feaure is not mine but that of FOMOCO on the FGT Wixom build sheet (Station #W10). Was it there just to "scare" assembly personnel to really make sure you torque this nut correctly? Unlikely in my estimation. The build sheets are peppered with critial torque callouts. The assembly line person had to enter in the build book the actual rear axle nut values to which the nut was torqued.
I am always reluctant to think I know more about the design than the engineers who actually produced the design.
Let's discuss this further with Mr. Alman next week at the rally. He should have a pretty good idea the consequences of torque relaxation on this stubshaft nut.
Oh, and Frank this is what is called a "technical discussion", or possibly peer review, not viewed by those in the engineering community as a questioning or challenging of one's opinion.:biggrin
andymlow
GT Owner
sahlman
Ford GT Team Alumni
OK, I went back and verified my memory with some drawings and reviewed comments by Bill, Ralphie and all. Bill and Ralphie are both correct (is this possible?!), although, from Ford's perspective the rear axle nut torque is a Critical Characteristic, meaning it is very important and can lead to unacceptable failure. So Bill is correct in his statement that this a very important torque. This is actually considered a drivetrain part/responsibility (thank goodness for us chassis guys) because it transmits drive torque and retains the half-shaft, but not the suspension/hubs/brakes/wheels.
At the same time Ralphie is correct in his statement that the axle nut retains the drive axle only. The front and rear hubs are identical part numbers with the difference being the rear axle engaging the hub splines at the rear (not the brake rotor). The hubs are self-contained units in which the rotor bolts to the hub with 3 small screws and the wheel and lugs further retain the brake rotors.
However, loss of torque and this nut could cause the stub shaft to shock load the splines destroying them (or possibly slip out of the splines) and disengage the hub then lose drive/engine braking. If this happens on one side and not the other (or one before the other), then loss of car control is quite possible (whether on or off throttle). And Murphy says it won't be when you are driving in a parking lot. Torque reversal (going from accelerating to braking or vice versa) is most likely when this would happen since constant drive or braking torque will likely "lock" the splines together.
I am not sure if this stub shaft can come all of the way out of the hub so I won't speculate on further issues if it does.
Bottom line...I would check the rear axle nut torque mark alignment every time the wheel is off and at least annually. Topshot's practice of torqueing it before every track event is a very good idea. Sticky tires (Hoosiers and such) along with significantly high HP's were definitely not tested on the program, which may be contributing factors to loss of torque (although sounds like it is happening on non-tracked fairly stock cars as well). Unfortunately, I am not sure why this nut is losing torque, but I was not involved in testing or specifying the design and torque level.
I hope this helps a little...and reinforces that Bill and Ralphie are good guys to give advice on the FGT!
Scott
At the same time Ralphie is correct in his statement that the axle nut retains the drive axle only. The front and rear hubs are identical part numbers with the difference being the rear axle engaging the hub splines at the rear (not the brake rotor). The hubs are self-contained units in which the rotor bolts to the hub with 3 small screws and the wheel and lugs further retain the brake rotors.
However, loss of torque and this nut could cause the stub shaft to shock load the splines destroying them (or possibly slip out of the splines) and disengage the hub then lose drive/engine braking. If this happens on one side and not the other (or one before the other), then loss of car control is quite possible (whether on or off throttle). And Murphy says it won't be when you are driving in a parking lot. Torque reversal (going from accelerating to braking or vice versa) is most likely when this would happen since constant drive or braking torque will likely "lock" the splines together.
I am not sure if this stub shaft can come all of the way out of the hub so I won't speculate on further issues if it does.
Bottom line...I would check the rear axle nut torque mark alignment every time the wheel is off and at least annually. Topshot's practice of torqueing it before every track event is a very good idea. Sticky tires (Hoosiers and such) along with significantly high HP's were definitely not tested on the program, which may be contributing factors to loss of torque (although sounds like it is happening on non-tracked fairly stock cars as well). Unfortunately, I am not sure why this nut is losing torque, but I was not involved in testing or specifying the design and torque level.
I hope this helps a little...and reinforces that Bill and Ralphie are good guys to give advice on the FGT!
Scott
Thanks Scott for supporting us and our car!
Just unparalleled to have the actual engineers on the FGT design team provide insight on the technical aspects of our car..
I am sure Ralphie and I will discuss this further with you in a few days at the Rally.
Just unparalleled to have the actual engineers on the FGT design team provide insight on the technical aspects of our car..
I am sure Ralphie and I will discuss this further with you in a few days at the Rally.
bonehead
GT Owner
Had the wheels off yesterday and the witness marks on the left rear axle nut were off. The other three corners were fine. Thanks for the heads up on this issue!