RexSeven UberDork
May 27, 2014 9:26 p.m.

Yesterday, I tried and failed to replace the rear axle cover on my '13 V-6 Performance Pack with the finned-aluminum Shelby GT500 piece. The RTV'ed rear cover is very hard to remove when you have only jackstands for ground clearance. What's worse, though, is that I noticed the pinion seal is leaking.

I'm guessing my Steeda Ultralite springs may have something to do with this. They have a 1.5" drop in the rear. The upper and lower control arms are stock on this car (standard crappy stamped steel UCA and GT500 LCAs). I had hoped the stock 2-piece driveshaft and GT500 LCAs would have given me some wiggle room, but apparently this is not the case.

I've read that an aftermarket adjustable UCA and LCAs are needed to correct the pinion angle to hopefully stop the pinion seal from leaking again. How do I measure the pinion angle so I can set it correctly? Also Sky_Render mentioned in my Mustang build thread that using only an UCA for pinion correction is a bad idea. Any elaboration on that?

Ranger50 PowerDork
May 27, 2014 9:37 p.m.

Adj lowers correct wheelbase variations. Upper fixes pinion angle.

As far as I see, that seal is just junk. Pinion angle won't really cause a leak unless it's extreme. I have seen some seals blow because the vent gets blocked and can't bleed off the pressure.

44Dwarf UltraDork
May 28, 2014 10:36 a.m.

Once the seal leaks it normally toast. You can check the angle several ways best way is using a magnetic angle cube on the drive shaft flange as that should be 100% perpendicular to the pinion shaft. You can also check the housing it self off the cover surface.

stanger_missle HalfDork
May 28, 2014 10:52 a.m.

I'd have to agree with what was said here. If the pinion angle was too sharp, you would feel it. It puts a lot of stress on the u-joints and makes the drive shaft very unhappy. In extreme cases, it will cause the u-joints to fail and the drive shaft to leave the car in a spectacular fashion.

In your case, I'd say that the seal was bad from the factory. It happens. The bad part is that you have to tear the whole differential apart to get the pinion seal out. Your Mustang should still be under warranty right?

RexSeven UberDork
May 28, 2014 7:42 p.m.

Yes, it is still under warranty. It's going in on Friday. I just hope the dealership doesn't give me any trouble for the springs as they may try to say that was the cause of the pinion seal leak.

Since they will need to get the rear differential cover off, I plan to ask them if they are willing to install the GT500 cover in place of the stamped steel cover, seeing as it is a Ford part and all.

Ranger50, I'd be surprised if the axle vent was clogged, because it has been spewing fluid since day one! Apparently this is a common problem with the 2011+ Mustangs, even when they are driven gently. I don't beat on my 'Stang. I've been trying to rectify that by bringing it to autocross, but other stuff gets in the way of that happening.

Ranger50 PowerDork
May 28, 2014 9:24 p.m.

I've never drained a diff to replace a pinion seal. What I do do is to apply some anaerobic sealer on the outside surface of the seal to combat any machining/manufacturing errors.

RexSeven UberDork
May 28, 2014 9:43 p.m.

How do you fill an 8.8 with the stock diff cover anyways, since there's no fill plugs? Do you take off the axle vent and pour it into there?

stanger_missle HalfDork
May 28, 2014 10:37 p.m.

Rule of thumb is to remove the fill plug and fill it up until it starts to run out.

8.8s are messy for doing fluid changes since there is no drain plug. The only way is to remove the diff cover.

RexSeven UberDork
May 28, 2014 10:49 p.m.

And that's why I want to swap in a GT500 differential cover. Well, besides the greater cooling capacity and fer lookin' purdy.

See, fill and drain plugs! That's not so hard, now is it, Ford?

Kenny_McCormic UberDork
May 28, 2014 11:28 p.m.

I'm not seeing how pinion angle would have caused a seal failure, without somehow toasting the pinion bearing first. Check that the vent is clear, it might stop leaking if that's the cause.

Also, the bigger 6 ton stands are your friend here, if your jack can't reach that high, put it on the 3 ton stands, then put the jack on wood blocks to get more height to slip the 6 ton stands under.

novaderrik PowerDork
May 29, 2014 4:50 a.m.

what is so hard about getting the cover off with just jack stands? put the stands under the frame and let the axle hang down, should be plenty of room... the cover should just pop off with a hammer and a chisel, but might need to use a sharp putty knife to break the seal- just make sure you leave a couple of bolts in loosely at the top of the cover so the whole thing doesn't fall into your drain pan along with a couple of quarts of gear oil all at once- even when it's new, that stuff is nasty..

Ranger50 PowerDork
May 29, 2014 6:25 a.m.
RexSeven wrote: How do you fill an 8.8 with the stock diff cover anyways, since there's no fill plugs? Do you take off the axle vent and pour it into there?

Fill plug is in the one side of the pinion case above the "fin". It's a square end plug, unless they have changed it to an Allen hex.

stanger_missle HalfDork
May 29, 2014 6:29 a.m.

So out of curiosity, I did a quick search for pinion seal issues for the '11-13s. There is literally a TON of people having issues with the pinion seal leaking. Also, Ford issued a TSB for the vent tube leaking. It looks like they redesigned the vent to a turkey baster design to prevent gear oil from coming out of the vent. However, the rubber bladder is vulnerable to heat damage on lowered cars due to the proximity of the vent to the tail pipes.

One of the suggested fixes is to install the GT500 diff cover for the extra fluid and cooling capacity. I couldn't find any TSBs for the pinion seal despite many complaints of it leaking.

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