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Discussion Starter #1
Getting my 2000 LT with 35K miles on it ready for a trip to the west coast from MN.
Did the final drive oil change and found this on the drain plug magnet.
No grinding, or play in the wheel.
Is there a concern?

The tip of a pen is for reference. Hope the picture quality is good enough.
 

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Old Slow Guy in A Fast Car
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I would say you are about to have a FD failure very soon & I would NOT take it on the trip till fixed. A little "Paste" type of material on the magnet is OK but pieces of metal like that is another story.
 

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Oh yes, that is a big concern. A little very fine fuzz on the magnet is pretty normal, but any pieces at all like shown in your picture is a harbinger of a failing drive, probably pretty soon. May as well get ready to replace/rebuild it right away. There are often used drives on eBay, or at Beemerboneyard, but be aware you have to have one from a 1999-2001 LT, since 2002 and later do not have the speed sensor mounting hole.

CharlieVT (Curtis) on list here has done a few rebuilds, I would see if you could send it to him before trusting a dealer rebuild. He seems to have a good method of measuring the the bearing pre-load, which some dealers may not do.
 

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Discussion Starter #4
CharlieVT
Sent you a PM, regarding a drive.
 

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Hi Jim,
This post comes after my PM back to you.
I just got around to looking at the picture in this thread.
Yeah, does not look good.
Based on drives I have looked at I'll bet your crownwheel bearing balls and races are starting to pit.
I don't think you'll go far without more problems. Better not to ride it at all IMO.



jaskjb said:
Getting my 2000 LT with 35K miles on it ready for a trip to the west coast from MN.
Did the final drive oil change and found this on the drain plug magnet.
No grinding, or play in the wheel.
Is there a concern?

The tip of a pen is for reference. Hope the picture quality is good enough.
 

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As a clarification, black fuzzies like those seen soaked into the cloth are normal. Anything with a visible size and shine to it indicates failure is imminent. You are actually quite lucky to have caught it so soon before a large amount of damage occurred.
 

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CharlieVT said:
Hi Jim,
This post comes after my PM back to you.
I just got around to looking at the picture in this thread.
Yeah, does not look good.
Based on drives I have looked at I'll bet your crownwheel bearing balls and races are starting to pit.
I don't think you'll go far without more problems. Better not to ride it at all IMO.
+1. that looks awfully similar to the shaving I got when mine FD went south
 

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I agree you caught it very early & by all means replace it NOW using one of CharlieVT units or at least his method.

Save this bearing, cut the outer race over, and post detailed pix of the running lines of contact of the races. This could be very valuable for the group to diagnose. I'd really like to see the results.

Is there any wiggle in the back wheel bearing system presently?
 

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Discussion Starter #9
So far there has been no evidence of bearing failure. No wiggle, noise or anything.
Since I change the final drive gear oil (synthetic) with every oil change, I just came across this. One could argue that I change the fluid too often, but I figure that a quart of gear oil is alot cheaper that a catastopic failure on the road somewhere. Looks like it paid off this time.
 

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dshealey said:
Oh yes, that is a big concern. A little very fine fuzz on the magnet is pretty normal, but any pieces at all like shown in your picture is a harbinger of a failing drive, probably pretty soon. May as well get ready to replace/rebuild it right away. There are often used drives on eBay, or at Beemerboneyard, but be aware you have to have one from a 1999-2001 LT, since 2002 and later do not have the speed sensor mounting hole.

CharlieVT (Curtis) on list here has done a few rebuilds, I would see if you could send it to him before trusting a dealer rebuild. He seems to have a good method of measuring the the bearing pre-load, which some dealers may not do.
Dave is right but there is more. Some dealers who know how to re-shim a final drive don't always do it unless they are pressed with embarrassing questions. Be your own advocate. Make sure your repair is done right, and by some one who cares.
 

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Judging bearing status from drain plug shavings

I've rebuilt between 20 and 30 final drives at this point. A few were preemptive rebuilds but most were failed crownwheel bearings.

Based on what I've seen, I make the following observations:

Grey "mud" on the drain plug is not a big concern. I suspect this fine metal powder is normal wear, especially when seen on a newer drive. I would expect the amount of this material to decrease as the drive wears in; I know I have noted this when changing the lube on my own drive. (However, and this is speculation not observation, it stands to reason that increasing amounts of this grey mud on the drain plug during subsequent lube changes may presage eventual further signs of bearing degradation.)

Metal particles that reflect light, glisten or sparkle are not normal and are signs of ball and race degradation. The presence of these shiney particles correlates very well with the presence of pitting on balls and races.

Shiney metal particles with little slivers of metal is an indication that the retainer has also started to degrade, this follows degradation of the balls and races. Presence of slivers is always accompanied with the shiney particles associated with ball and race degradation. (This is why the idea that the problem was with an inferior retainer is incorrect; the retainer fails secondary to stress put on it by pitted balls and races. It would be unusual to find metal slivers from the retainer during a routine lube change because once the retainer starts to degrade it is probably a very short time before the oil seal is damaged by the broken retainer.
 

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Re: Judging bearing status from drain plug shavings

CharlieVT said:
-------------------------snipped--------------------------- (This is why the idea that the problem was with an inferior retainer is incorrect; the retainer fails secondary to stress put on it by pitted balls and races. It would be unusual to find metal slivers from the retainer during a routine lube change because once the retainer starts to degrade it is probably a very short time before the oil seal is damaged by the broken retainer.
I sent two failed bearings to a bearing engineer at one of the major bearing manufacturers, and that was what he said, that the balls hitting the brinelled spots (likely caused by poor drive manufacturer's processes) made the balls repeatedly load and unload the retainer as the ball race failure proceeds, causing it to fail. The failed retainer is a symptom of ball/race failure, not the retainer failing first.
 
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