Setting a 9 in rear....

[grant_71]

Ok after my build i have about 600 miles on my truck, fresh motor and rebuilt rear end, the rear is a 77 BB 3.50 open while i was replacing seals last night on the axle shafts i noticed that the gear oil is looking pretty metallic colored. The oil itself looks like dark silver metallic paint (if you mixed it you know the color effect i am talking about) and the sludge in the bottom of the axle housing (yea sludge already....) comes out looking like anti-seize with some metal pieces about the size of a grain of sand. My dad and i had never set up a 9in before but we bought the kit and all the tools and went by the book for setting it up and it all checked out fine. i don't see any excessive wear on the ring or pinion, the bearings all seem good, and there is no excessive backlash. I am thinking of taking the third member into a drive line shop just to see what they say, but i wanted to know what is normal break-in for a rear end. Thanks

Grant

 

[trailpsycho]

I think a little metal is somewhat normal. I would change the gear oil and check it again in another couple hundred miles. My plan is to change all the fluids after 400 or so miles...on everything....everything.

 

[grant_71]

Thanks that is what i wanted to hear/know. After this last weekend i was going to go back over everything now that i have a few miles on it and change engine oil since it is a fresh 302 and clean out the rear axle housing and i will dump some fresh standard 90w oil in it. I was going to switch to synthetic, but i may wait a little longer.

Grant

 

[broncodude_73]

we set up gears all the time and recommend to everyone change your fluid after 500 miles of wear.

 

[trailpsycho]

Thanks that is what i wanted to hear/know. After this last weekend i was going to go back over everything now that i have a few miles on it and change engine oil since it is a fresh 302 and clean out the rear axle housing and i will dump some fresh standard 90w oil in it. I was going to switch to synthetic, but i may wait a little longer.

Grant

Yeah, I should have said that as well...start with conventional...then switch over to synthetic....not sure there is any advantage of doing 2-500 mile intervals or a 500 and 1000 mi interval with conventional then switching it over. I would rather be safe than sorry, but at the same time, no need to go overboard.

Oh yeah, too late.... Anyone with any opinions on multiple short intervals before switching to synthetics?

 

[ugly74]

my opinion...I'd do short intervals with regular oil, like every 300-500 miles, until you quit finding metal in the oil. at that point, the wear surfaces have "work hardened", and you'd be safe going to synthetic.
If I ever rebuild any of my diffs, that's the plan I'm going to run with.
I'll most likely epoxy a round flat magnet somewhere towards the bottom of the housing to try and catch the metalic dust floating around too.

 

[phred]

Did you temper the gear set before you put a load on it?

We always run a new gear set for about 20 miles after and install and then let it cool over night to temper it. Then drive it under normal loads for 500 miles to let it all set in before putting excessive loads like towing or offroading. Never had a new set fail that has been done this way.

 

[grant_71]

Did you temper the gear set before you put a load on it?

We always run a new gear set for about 20 miles after and install and then let it cool over night to temper it. Then drive it under normal loads for 500 miles to let it all set in before putting excessive loads like towing or offroading. Never had a new set fail that has been done this way.

Gears were not new, they were originals, just put in new everything else, it had a good 500 miles on before this weekend and the wheeling was not really hard at all, just some dirt roads and two tracks...little sand

 

[DirtDonk]

Although your description of the metallic look of the lube seems somewhat normal (especially if you'd had a limited slip and new gears), your mention of sludge is not. Do you think it could have been some old crud finally coming to rest, or is it strictly new crud?
If new, could your setup have overheated during it's first few miles perhaps? Even that doesn't seem like enough to cause sludge buildup in such a short time, but it's a thought.
The fact that your gears still look good is a good sign, but I thought I'd ask about the overheating possibility.

Paul

 

[grant_71]

Although your description of the metallic look of the lube seems somewhat normal (especially if you'd had a limited slip and new gears), your mention of sludge is not. Do you think it could have been some old crud finally coming to rest, or is it strictly new crud?
If new, could your setup have overheated during it's first few miles perhaps? Even that doesn't seem like enough to cause sludge buildup in such a short time, but it's a thought.
The fact that your gears still look good is a good sign, but I thought I'd ask about the overheating possibility.

Paul

I doubt the over heating, no real reason for it, still plenty of oil, but who knows.
The sludge is pretty much just more of the metallic crap only a higher concentration of metal, looks like antisieze, there is no old sludge as i had the housing completely disassembled and cleaned, it still is pretty clean as well.
I guess the main thing is i just wondered if this is normal or not. I am thinking changing the oil and running it some more and go from there

Grant

 

[DirtDonk]

Ok then, sounds like a happy ending. Even though it seems to have built up awful quick, that anti-sieze looking crud is pretty normal.
I've had it at the bottom of my transmission and transfer case also, and they were in perfect shape. Not so much in my diffs (oddly enough), but it definitely sounds like a gear kind of thing.

Sounds like you're in pretty good shape.

And I waited 5000 miles before changing my diffs to synthetic, but I was just being cautious.

Paul

 

[SaddleUp]

It's normal to get metal particles after setting up a "NEW" set of gears before they temper which usually occurs within 500 miles or so. I usually run a new set for about 1000 miles and then change the gear oil. This is not normal though for a used set of gears as they are already tempered from previous use. Could the sludge have been up in the axle tubes and then settled down into the bottom? That could explain both if the previous installation never had the oil changed after the gears were broke in. I would change the gear oil now and then drive it a few hundred miles (First do a pattern check on the gears to be sure the pattern still looks good) and change it again. If it still has a little metal particles in it then don't worry too much but if it looks like it does now again then I would be concerned.

 

[grant_71]

Could the sludge have been up in the axle tubes and then settled down into the bottom?

Hehe..no, when I said clean...I meant completely disassembled bare housing stood on end in a parts washer, steam cleaned, media blasted and covered in chassis saver (which is rusting....this truck has never seen rain or salt). I understand what you are saying about the temper and normal metal particles, good call i will check the pattern again tonite. My back lash seemed to be good still. I am beginning to wonder if the metal is coming from the coast side of the gears....Now that i think about it, when i let off the gas or down shift there is loud whiney rumble, (basically sounds like straight cut gears) that i have been thinking was the transmission (it is the only part of the driveline that was not rebuilt) but now i got me thinking it may be the rear. if i even give the slightest amount of throttle the noise goes away (taking the load off the coast side)....I will let you know what i find tonite before i button it back up.

Grant