continued axle leaking

[stevbd]

I have a 2011 GT that, as usual, was leaking diff fluid out of the vent cap on the right side of the axle during track events. So I installed the finned Boss/FRPP diff cover that has the baffled vent on the top of the cover, plugged the original vent hole, and filled with 2.5 qts oil. All seemed good for a couple events but now fluid seems to be leaking out at the right side hub. The axle is dry and it's not leaking out of the vent. But this only is happening on track. It seems if the axle seal was bad, it would leak all the time. And if the new setup isn't venting properly, and the axle is getting too much pressure, it should leak from both sides, right? One weird thing, I have that "turkey baster" vent that Ford sells, - which I originally (and unsuccessfully) tried to use in the original vent location - installed on the top of the diff cover. Does that turkey baster restrict ventilation perhaps?

I'm stumped, any help appreciated. Thanks!

 

[VoodooBoss]

I don't have an answer for you but check the thread below. If you put a full 2.5 quarts in it that could be too much if it wasn't drained fully. See post #17.

https://trackmustangsonline.com/threads/how-much-gear-oil-did-your-diff-take.12839/

 

[stevbd]

Yeah, I read that thread. The axle and diff were fully drained when I replaced the diff cover so I think I'm good there.

 

[F.D. Sako]

Just go to an open vent setup, without a valve. Put a hose on the left axle tube and route it up along the gas fill hose into the tirewell, do a couple of loops and zip tie it there. I have a fuel filter at the end to prevent dirt going in the axle housing. I think the turkey baster has some sort of a valve on top that could potentially fail and not vent.

 

[VoodooBoss]

Sako nailed it.

 

[Grant 302]

Sounds like either the vent is not venting, or the axle seal is bad. The seal doesn't have to leak all the time to be bad, IMO.

 

[TMSBOSS]

The turkey baster has worked well for some. I went with a vent can mounted to the body with a line to the vent on the axel.
Sounds like you have a bad axel seal. Is it from overpressure caused by the lack of ventilation? Likely not. I have burned up a seal on track before. Will likely happen again.
Be sure you are filling to the hole in the front of the diff "Pumpkin". Its easy to over fill our diffs and contribute to leaking and fluid discharge issues.
I change both seals, right and left, at the same time. Most of the expense is the gear oil. A second seal is not that expensive.

 

[BigTaco]

Yes, you have to do almost the same amount of work to do one seal, do them not for good measure....

 

[wwilde001]

+1 on a bad axles seal. I had one go bad after tracking the car for a year. No rhyme or reason. Good Luck!

 

[TMSBOSS]

One thing which contributes to axel seal failure is rear brake temps. The rear brakes have little cooling air circulating around them. Have you removed the factory shields from the rear? Its mentioned in the Boss supplement as a step needed before tracking our cars Boss or GT. I smoked one at Road America. Three long high speed sections with heavy braking zones, every lap. Very hard on the seals. I have also switched to the 13" GT500 rear discs. More surface area an inch further from the seals.

 

[Grant 302]

I have a 2011 GT that, as usual, was leaking diff fluid out of the vent cap on the right side of the axle during track events. So I installed the finned Boss/FRPP diff cover that has the baffled vent on the top of the cover, plugged the original vent hole, and filled with 2.5 qts oil. All seemed good for a couple events but now fluid seems to be leaking out at the right side hub. The axle is dry and it's not leaking out of the vent. But this only is happening on track. It seems if the axle seal was bad, it would leak all the time. And if the new setup isn't venting properly, and the axle is getting too much pressure, it should leak from both sides, right? One weird thing, I have that "turkey baster" vent that Ford sells, - which I originally (and unsuccessfully) tried to use in the original vent location - installed on the top of the diff cover. Does that turkey baster restrict ventilation perhaps?

I'm stumped, any help appreciated. Thanks!

Put the metal vent back on to the diff cover first, IMO. I don't think the turkey baster is a good idea at the top of the diff. Not sure how it should even fit up there without contacting the floorpan/axle hump.

 

[stevbd]

Thanks for all the responses. When I replaced the diff cover I also did the GT500 rear brakes but it seems I messed up the job in a few small but important ways.

First, I didn't replace the axle seals when I was in there because they seemed good and I was rushing. Stupid. I also didn't remove the brake backing plates, I didn't realize that was called for. (By the way, is there any reason to keep the backing plates? I track this car but it's also my daily driver.) Then I used the turkey baster because I didn't have a metal vent cap on hand. So I will go back and do this over and fix all my mistakes. It's not really too bad a job but I'm especially annoyed at myself not to have replaced those seals while I had everything apart.

Anyhow, thanks for all the help and comments, much appreciated.

 

[06mach1]

I've used the turkey baster with the metal breather in the top of it from day one in my boss and have never had it blow out the breather. I do end up changing the axle seals once a year. Also, very important, make sure your oil level is 1/2 below the front fill plug.

 

[TMSBOSS]

Backing plates are a good idea for a street driven car. The plate prevents rocks and other crud from getting between the rotor and calipers. They also restrict air flow. No problem so far on my Boss

 

[blacksheep-1]

Next time you pull the axle, place a straightedge across the area where the axle runs on the bearing, it may look fine but still be worn.

 

[stevbd]

Next time you pull the axle, place a straightedge across the area where the axle runs on the bearing, it may look fine but still be worn.

Sorry to be slow but I don't quite understand the technique you are describing. Are the axle bearings a "while you're in there" replacement part? My car has 65K miles. Thanks for the help.

 

[blacksheep-1]

OK, long story, my first experience with the 8.8 was that Ford made the 9 inch, which is a world beater, then they decided to copy the crappiest parts of the GM10/12 bolt diffs when they went with the 8.8. Besides not having a removeable banjo, they also discard the axle retaining feature of the 9 inch and use the GM style (bearing rides on the axle) method , which means the axle wears out and there's no retention feature. I've had 8.8 axles go bad in 30k miles in a street vehicle. When you pull the axle, next time, look closely where the axle wears on the wheel bearing, the rollers actually ride on the axle, (instead of a totally contained bearing that is pressed onto the axle) When you view the axle , flange on right, splines on left, you need to put a straight edge on the point where the axle rides in the bearing, even though you may not see it with the naked eye, or feel it with your fingernail, any light shining between the straightedge and the bearing indicates excessive wear. The axle flopping around like that will degrade the seal.
That would tell you that you also need a new bearing and seal.
Oh yeah, if the inside retainer clips are worn down they can cause the axle to slide slightly in and out, along with the wear, this can also contribute.
Hope that did it.

 

[F.D. Sako]

Might as well replace the bearings when you pull the axles out for the seals.

I bought one of these and attached it to a slide hammer, took both the seal and bearing out at once. Here's a ford bearing/seal kit, conveniently sold together.

You'll probably want to replace the LSD shaft bolt and axle c-clips (Ford Part No. 4N237)


Here's my thread when I went through that ordeal.

 

[SPDBOSS]

Gents, I have a question related to leaking axle seals. The left rear started leaking at the track. Once back in my garage, I pulled the seals and bearings and inspected everything. Axles and old bearings look good. However, the inside of the axle tube, about 1/2 to just inside from where the bearing sits is scored. Looks as if a rotating mass did the scoring. However, the axle should never come in contact with the housing since the bearing centers it. There were some very small metal particles in the tube as well. Again, the axles look good, straight edge and flashlight method. Anyone ever see scoring in the tube?

 

[xr7]

sounds like the type of damage that can be done by a broken axle.