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Metal chips in differential

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303
251
Exp. Type
HPDE
Exp. Level
3-5 Years
25 min. to 1½ hrs. from Sonoma (ugh... traffic!)
So, I drained my differential and found a fair amount of metal particles on my magnetic drain plug.

20220421_103748_HDR_(1)[1].jpg

This is after about 5 hours of track time and a few hundred street miles. After my last track day I noticed an oil stain developing at the r/h wheel bearing so I'm in the process of pulling the axles. I don't think think the seal is leaking because of a plugged axle vent, my Cortex catch can has been puking oil all over the underside of the car so I'll be addressing that somehow too. I'm guessing the seal failure is caused by some bearing wear, maybe the source of these chips too?
Bearings and seals will be replaced but I'm wondering if there's anything else I should be looking for while I'm in there?
 

PaddyPrix

If breakin' parts is cool, consider me Miles Davis
725
1,081
Exp. Type
Time Attack
Exp. Level
Under 3 Years
San Diego
Torsen or track lock?
Good call. When you get on the track, do you do it in normal, sport, or track? A Torsen would have worm gear/wheel, but Trak Lok would have clutch packs which are a wear item.
 
6,363
8,189
So with regards tot he axle bearing, one of the great failings of the 8.8, which is actually a pretty good diff in all other respects, is the bearing rides on the axle, like a GM 12 bolt, it doesn't have it's own bearing race like the 9inch Ford. The reason I mention that is because when you take those axles out there is about a 50% chance that you will need to replace them. Put a straight edge where the bearing rides on the axle and look for pitting in the same area.
 
303
251
Exp. Type
HPDE
Exp. Level
3-5 Years
25 min. to 1½ hrs. from Sonoma (ugh... traffic!)
Torsen or track lock?

Good call. When you get on the track, do you do it in normal, sport, or track? A Torsen would have worm gear/wheel, but Trak Lok would have clutch packs which are a wear item.
Track lok, and I usually turn advancetrac off (to the extent possible). I have forgotten to do this more than once though :oops:

Update: I drained the diff and didn't see any more metal. Pulled the caliper and rotor off the r/h side and upon closer inspection I don't think that the axle seal was the source of my oil stain, I suspect I spilled a small bit of brake fluid there when I flushed them prior to my last event.
That being said, I can feel the slightest amount of radial play at the bearing, a couple thousandths or enough to feel/hear but not see, left side is about the same. I cant find any specs in the Ford workshop manual for this. Bearing rotates smoothly and without noises. 28K and a dozen track days on 'em.
What would you guys do, pull the bearings anyway or send it?
 
303
251
Exp. Type
HPDE
Exp. Level
3-5 Years
25 min. to 1½ hrs. from Sonoma (ugh... traffic!)
Yep, I've seen them fail under 20K
It appears the outer end of the axle is a bit narrow in the center when gauged with a wide straight edge that spans beyond the bearing contact area, but looks pretty darn good with a narrower one. 2 or 3 barely visible pits. Confirmed seal was not leaking too. I'll press a new bearing and seal, and reassemble, unless I'm missing something...20220424_165257_HDR.jpg20220424_165624_HDR.jpg
Still wondering if the amount of chips I found are a big concern.
 
303
251
Exp. Type
HPDE
Exp. Level
3-5 Years
25 min. to 1½ hrs. from Sonoma (ugh... traffic!)
IMO, That axle is done for... sorry.
The pits are the key.
Don't get me wrong, it will live for awhile longer, but it's definitely pass the 50% mark on longevity.

What he said. Dump the pits. Sorry.
I looked into Ford axles a few days ago and found prices of ~ $300-$500 ea. Of course the lower end is backordered. Thank you guys for your input, I must have been suffering from some wishful thinking, impatience to be prepared for my next event, and maybe some disbelief that axles could wear so much this soon. Funny thing is this would have got no notice if not for a brake fluid stain being misread as seal leakage. I cleaned things up a bit more, used the right glasses and took a closer look:

20220425_121906_HDR.jpg

If I can get replacements in a week or two I'll be fine. Does anybody know if the Ford axles have the wheel speed rings on 'em? (I might need one). And what's the O-ring in the U-washer groove do?

@blacksheep-1. While I'm a fan of my Cortex Watts Link, you can add axle maintenance to your list of cons. ;)
 
6,363
8,189
I looked into Ford axles a few days ago and found prices of ~ $300-$500 ea. Of course the lower end is backordered. Thank you guys for your input, I must have been suffering from some wishful thinking, impatience to be prepared for my next event, and maybe some disbelief that axles could wear so much this soon. Funny thing is this would have got no notice if not for a brake fluid stain being misread as seal leakage. I cleaned things up a bit more, used the right glasses and took a closer look:

View attachment 75195

If I can get replacements in a week or two I'll be fine. Does anybody know if the Ford axles have the wheel speed rings on 'em? (I might need one). And what's the O-ring in the U-washer groove do?

@blacksheep-1. While I'm a fan of my Cortex Watts Link, you can add axle maintenance to your list of cons. ;)
They do have the speed rings on them. Like I said, those will live a bit longer but they are on their way out.
 
303
251
Exp. Type
HPDE
Exp. Level
3-5 Years
25 min. to 1½ hrs. from Sonoma (ugh... traffic!)
I haven't pulled them out yet to see. I've been short on time and focusing on the axle issue. I have the bearings and seals, will find out soon while waiting on axles.

This from Timken:

______________________________________________________________________________________________________________________________
bearing damage.jpg
__________________________________________________________________________________________________________________________________

Fig 7 shows a bit more severe case of what I see here. I did have a fair amount of chips on my magnetic drain plug, I'm not feeling reassured that even replacing the axles will be the end of this story.
 
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TMSBOSS

Spending my pension on car parts and track fees.
7,530
5,247
Exp. Type
HPDE
Exp. Level
10-20 Years
Illinois
Any chance an axel replacement, like with a adjustable camber unit from Cortex is in your future? You are likely in the $500-750 range right now and you have not looked at the carrier or pinion bearings. Painful, yep. Just a thought.
 
179
309
Utah
Also with the track lock, the axle will gain play into and out of the axle as the track lock clutches wear. There is a spec for the allowable play. Since you have the cover off, you may want to clean inside under the gearset. If there is metal on the fill plug, there is likely debris settled at the bottom.

Having done several rear axles, I don't think I have seen the axle surface wear out before the carrier and pinion bearings. I re-geared my axle over the winter and the pinion and carriers were pitted, but the axles were OK. Others can comment on that as they may have more experience.

If you have some money to spend, look at a Torsen (or equivalent helical) for any track work at all. Especially if you end up having to rebuild the center bearings.
 
303
251
Exp. Type
HPDE
Exp. Level
3-5 Years
25 min. to 1½ hrs. from Sonoma (ugh... traffic!)
If you have some money to spend, look at a Torsen (or equivalent helical) for any track work at all. Especially if you end up having to rebuild the center bearings.
This is on my mind. I've done everything else on this car myself. I have the aptitude and ability to learn, but differentials, transmissions and computers are like black magic boxes to me 😵
 

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