changed diff fluids - is this normal?

[BK_89iX]

'97 explorer 4L SOHC, 4x4, 3.73 limited slip in the rear. Bought it new and it now has 93k miles.

Changed out the fluid in both differentials today:

Sucked out the front (major PITA through a small tube) and installed Mobil 1 75W90 synthetic. Old fluid was dark, but nothing out of the ordinary. Spent a lot of time making sure I got out as much of the old stuff as I could. By volume I got all of it.

On to the rear. Fill plug came out without issue, but the magnet was packed with about 3/8" inch of a grey paste, which got me a bit worried. Pulled the cover and the fluid that drained out was a very clear honey color. Trapped down low there was a lot dark sediment stuff, and dark material coated the inside back of the cover and all internal parts. Invested a couple hours wiping down all the surfaces to get that crap out of there. Gear wear looked OK to me. Loads of gold colored metallic particles in my catch pan (brass?). Will fill with Mobil 1 75W140 synthetic tomorrow after the cover sealant cures a bit more.

Does the rear diff sound normal for 93k miles? What's the likely source of the gold colored metal particles? In retrospect I wish I would have changed out the fluids at half the mileage...

BK

 

[pdmustgt]

The grey paste like as you call it is normal. Gold/brass flakes theres nothing in there that should do that. If you are seeing bearing material that has slight gold tint to it. But if that was the case the magnet on the plug would be loaded as we call (hairy). From what I'm remembering the thrust washers behind the side gears and pinions are steel.

I've seen poeple dump "stuff" in a rear to try to make quiet or suppost to cushion the gears LOL

 

[BK_89iX]

I've had it since new, so no "magic" additives!

My catch pan is black plastic and the old fluid was a honey color, so perhaps the tiny metallic flakes/particles just appeared to be golden/brass colorerd in the light of the sun. I'll see if I can fish some out of the container and examine closer. Rear end was behaving normally.

I'm glad I pulled the cover. I would have never known about or removed that junk with a suction gun, and the ridges in the actual case casting prevented that stuff from flowing out with the bulk fluid. I needed to reach in and scoop the fluid from behind the ridges/wipe to really get to it. Mechanical TLC.

BK

 

[techieman33]

some of the the stuff in there is probably clutch material as well.

 

[Potomac30]

Was your differential cold when you dropped the cover? Maybe the trash precipitated out. I did my '93 at about 83K and I did it after it was warmed up. My fill plug was just like yours but the fluid was a thick, gray mess. I put cheap gear oil in it and changed it again at 100K. The second fluid change came out golden with no sediment or wear particles. I've got M1 75/90 in there now and I think that it'll be good for 100K if I don't tow too much or submerge it. One fluid change should do you. I think that most of the wear happens during break in. I had a 2000 Chevy truck that recommended that the differential fluid be changed after the first 5000 miles.

 

[BK_89iX]

Was your differential cold when you dropped the cover? Maybe the trash precipitated out. I did my '93 at about 83K and I did it after it was warmed up. My fill plug was just like yours but the fluid was a thick, gray mess. I put cheap gear oil in it and changed it again at 100K. The second fluid change came out golden with no sediment or wear particles. I've got M1 75/90 in there now and I think that it'll be good for 100K if I don't tow too much or submerge it. One fluid change should do you. I think that most of the wear happens during break in. I had a 2000 Chevy truck that recommended that the differential fluid be changed after the first 5000 miles.

I think you could be right. I set everything up to do it hot, but I spent so much time dealing with the front differential the rear was mostly cooled off by the time I made it to the rear. I got it done the hard way...lots of wiping. I like the idea of a cheap gear oil flush (Mobil 1 for both ends cost me $82!). Lifetime fill is just silly. I googled up pics of 8.8 L/S rear ends and I think the dark stuff I saw coating the inside is totally normal - probably clutch material as techieman33 mentioned. Metallic bits, who knows.

BK

 

[BK_89iX]

UPDATE!

Opened up the rear differential again today to replace the axle/wheel bearings. Measureed too much backlash at the gear, and small amout of L/R movement of the carrier. Pulled carrier and found the bearings totally shot. The races turned a nice bronze color, presumably from the heat/pitting/etc. That explains the gold particles.

BK

 

[pdmustgt]

There was a period that there was bearing material issue. My 99 mustang GT did this but we also had the same problem with rears in semi's from 98-01

 

[BK_89iX]

There was a period that there was bearing material issue. My 99 mustang GT did this but we also had the same problem with rears in semi's from 98-01

Very intersting. I've been scratching my head over why this happened, since the explorer has had a relatively easy life and I bought it new. Reminds me of the issue of "bad capacitors" in millions of electronic devices a few years ago...

BK

 

[pdmustgt]

We had so many that had side carrier bearing problem about 1/4 of them ruined the case. End up dropping in a whole carrier

 

[BK_89iX]

We had so many that had side carrier bearing problem about 1/4 of them ruined the case. End up dropping in a whole carrier

Before I put it back together, is there something else I should be inspecting? This is my first time into a differential....

BK

 

[pdmustgt]

Check all bearings in the rear clean the housing out good