Play/movement at one wheel when parking brake applied?

[coho66]

So I just had car up in the air with the wheels off to do a brake fluid replacement

Upon torquing the rear wheels with the vehicle still in the air and the parking brake engaged

(loved the lug nut extenders for anyone sitting on the fence about them https://steelmantools.com/products/...-tool-set-3-piece?_pos=1&_sid=1ecf8f0da&_ss=r )

I noticed that there is say 3/8" or whatever of radial movement in the rear left wheel/rotor while torquing?! This isn't seen in the right side and the parking brake is holding because it's only the ~ 3/8" play and nothing more and it still holds the wheel while I torque to 150 but the wheel moves very freely upon releasing the parking brake.

I'm trying to wrap my head around why the play is there

Why is it seen only on the left side and not the right

Whether that's normal or a problem that needs to be fixed?

Any thoughts/input?

 

[JP X]

So I just had car up in the air with the wheels off to do a brake fluid replacement

Upon torquing the rear wheels with the vehicle still in the air and the parking brake engaged

(loved the lug nut extenders for anyone sitting on the fence about them https://steelmantools.com/products/...-tool-set-3-piece?_pos=1&_sid=1ecf8f0da&_ss=r )

I noticed that there is say 3/8" or whatever of radial movement in the rear left wheel/rotor while torquing?! This isn't seen in the right side and the parking brake is holding because it's only the ~ 3/8" play and nothing more and it still holds the wheel while I torque to 150 but the wheel moves very freely upon releasing the parking brake.

I'm trying to wrap my head around why the play is there

Why is it seen only on the left side and not the right

Whether that's normal or a problem that needs to be fixed?

Any thoughts/input?

The left rear bearings are always going bad. It’s a thing, unfortunately.

 

[67GTA]

The left rear bearings are always going bad. It’s a thing, unfortunately.

I believe it’s the axle nut that backs off over time. I saw somewhere the fix is using 2 nuts on that side to create a jam nut.
Edit - just remembered where I read it - Trent Musser does this on S550’s - see explanation below;

 

[JP X]

I believe it’s the axle nut that backs off over time. I saw somewhere the fix is using 2 nuts on that side to create a jam nut.
Edit - just remembered where I read it - Trent Musser does this on S550’s - see explanation below;

View attachment 95647

I’ll try that. I’ve been periodically checking them, but still had failures.

 

[JAJ]

So I just had car up in the air with the wheels off to do a brake fluid replacement

Upon torquing the rear wheels with the vehicle still in the air and the parking brake engaged

(loved the lug nut extenders for anyone sitting on the fence about them https://steelmantools.com/products/...-tool-set-3-piece?_pos=1&_sid=1ecf8f0da&_ss=r )

I noticed that there is say 3/8" or whatever of radial movement in the rear left wheel/rotor while torquing?! This isn't seen in the right side and the parking brake is holding because it's only the ~ 3/8" play and nothing more and it still holds the wheel while I torque to 150 but the wheel moves very freely upon releasing the parking brake.

I'm trying to wrap my head around why the play is there

Why is it seen only on the left side and not the right

Whether that's normal or a problem that needs to be fixed?

Any thoughts/input?

The parking brakes on GT350's are completely different than parking brakes on other Mustangs. Owners of other Mustangs will provide guidance that does not apply to your car. This thread is full of it.

What you're seeing is normal on GT350's. The parking brake is designed to stop the car from moving, but there's a bit of play that allows both rear wheels to rotate "rearwards" a bit when the brake is on. The left side wheel does it when you torque the wheel nuts because the wheel is being turned "backwards". The right side does it too, but when you're torquing the nuts, you're turning the wheel "forwards" so it's locked in place and you don't feel it.

 

[67GTA]

Owners of other Mustangs will provide guidance that does not apply to your car. This thread is full of it.

What I posted is relevant to a known issue with the LR hub on the GT350s. And I wouldn’t consider torquing a 150 Ft lb nut using the parking brake to hold it normal.

 

[coho66]

You guys are bloody awesome

Thanks for the tips/ideas to start... Without tearing things apart I've been like Winnie the Pooh over this, and due to the horror stories of dealerships, I'd prefer to handle it myself if possible.

For any car I've worked on, I've always used the parking brake as a means to hold the rear wheels so I can torque the wheel true to the hub without the car's weight on it... It snugs together so much nicer and easier and no risk of bending studs or damaging threads.

I reckon if the parking brake is designed to hold the car's weight in place, surely the force of the wheel torque is going to be easy peasy, and I figured the act of me doing so tests the effect of the parking brake as well.

I'll examine the bearing.... It's good to know that's a idiosyncratic wear item for this chassis... If it is the bearing, it'd be pretty disappointing given it's only got 2000 miles on it, of which only 500 is from me.

I'll also examiner the axle nut. In my limited experience with them in the past, to prevent the nut from backing off, the nut was staked, but I'm not seeing a notch/groove/channel designed into the axle shaft to allow for that to happen.

 

[coho66]

The parking brakes on GT350's are completely different than parking brakes on other Mustangs. Owners of other Mustangs will provide guidance that does not apply to your car. This thread is full of it.

What you're seeing is normal on GT350's. The parking brake is designed to stop the car from moving, but there's a bit of play that allows both rear wheels to rotate "rearwards" a bit when the brake is on. The left side wheel does it when you torque the wheel nuts because the wheel is being turned "backwards". The right side does it too, but when you're torquing the nuts, you're turning the wheel "forwards" so it's locked in place and you don't feel it.

I was hoping it wasn't a mechanical issue and simply an idiosyncrasy like this

 

[JAJ]

You guys are bloody awesome

Thanks for the tips/ideas to start... Without tearing things apart I've been like Winnie the Pooh over this, and due to the horror stories of dealerships, I'd prefer to handle it myself if possible.

For any car I've worked on, I've always used the parking brake as a means to hold the rear wheels so I can torque the wheel true to the hub without the car's weight on it... It snugs together so much nicer and easier and no risk of bending studs or damaging threads.

I reckon if the parking brake is designed to hold the car's weight in place, surely the force of the wheel torque is going to be easy peasy, and I figured the act of me doing so tests the effect of the parking brake as well.

I'll examine the bearing.... It's good to know that's a idiosyncratic wear item for this chassis... If it is the bearing, it'd be pretty disappointing given it's only got 2000 miles on it, of which only 500 is from me.

I'll also examiner the axle nut. In my limited experience with them in the past, to prevent the nut from backing off, the nut was staked, but I'm not seeing a notch/groove/channel designed into the axle shaft to allow for that to happen.

Your bearing is fine. And the parking brake is more than adequate to take the torque of the wheel nuts. As I said, the GT350 parking brake is totally different than any other Mustang. It's a BMW-style drum brake located inside the rear brake rotor hat.



I borrowed this picture of a GT350 rear hub and brake assembly from Ebay. This is what you see when you take the rear brake rotor off. These parts are corroded but you can see the layout with the hub, the brake shoes, the springs and the adjuster. Presumably, having the parking brake setup both large and completely separate from the 380mm rear disk brake was done for a reason, drifting perhaps. In any case, the shoes are spring-loaded and held against a stop preventing the car rolling forwards, Of course, there's also a stop to prevent rolling back and there's a few degrees of slack between the two stops. The movement you feel when you tighten the lug nut on the left rear is rotating the drum brake backwards from one stop to the other. On the right side, it's already against the forward stop so it doesn't move, although you might feel it when you undo the rear lugs on that side.

As for longevity of the wheel bearings, there's a community out there that will happily tell you that GT350's are packed with stuff that will fail early and often. The solution, of course, is to change the wheel bearings every three months and pop in a new Voodoo every time the oil change light comes on.

 

[coho66]

I was hoping it wasn't a mechanical issue and simply an idiosyncrasy like this

I am/was aware of a design difference between the gt350 parking brake being different from the other trims

Namely

If I understand correctly, the brake being integrated into the rear caliper pistons

 

[67GTA]

You guys are bloody awesome

Thanks for the tips/ideas to start... Without tearing things apart I've been like Winnie the Pooh over this, and due to the horror stories of dealerships, I'd prefer to handle it myself if possible.

For any car I've worked on, I've always used the parking brake as a means to hold the rear wheels so I can torque the wheel true to the hub without the car's weight on it... It snugs together so much nicer and easier and no risk of bending studs or damaging threads.

I reckon if the parking brake is designed to hold the car's weight in place, surely the force of the wheel torque is going to be easy peasy, and I figured the act of me doing so tests the effect of the parking brake as well.

I'll examine the bearing.... It's good to know that's a idiosyncratic wear item for this chassis... If it is the bearing, it'd be pretty disappointing given it's only got 2000 miles on it, of which only 500 is from me.

I'll also examiner the axle nut. In my limited experience with them in the past, to prevent the nut from backing off, the nut was staked, but I'm not seeing a notch/groove/channel designed into the axle shaft to allow for that to happen.

Totally agree on getting the wheel tight against the hub before placing weight on it. It’s just that 150 ft lbs is a much higher torque than days of smaller studs and you’re placing that load on one brake at a time. I’m sure with such low miles that what you’re seeing is normal as per JAJ’s experience above, but throw the 2nd nut on there now as insurance to protect the hub as you track it more. All good.

 

[coho66]

As for longevity of the wheel bearings, there's a community out there that will happily tell you that GT350's are packed with stuff that will fail early and often. The solution, of course, is to change the wheel bearings every three months and pop in a new Voodoo every time the oil change light comes on.

I like the way they think. And here I've always felt out of place because my friends thought I was crazy for keeping a closet full of $100 bills to light my cigars with, while also shaking their heads at me for using cask strength 25 year old scotch for brake clean.

It's good to know I've finally found a place with like minded individuals.