Last year i had my front diff on my suburban rebuilt, not the ring/pinion,just bearings and stuff. The truck had 188K miles on it and im pretty sure it has not been serviced correctly. I bought it used. Anyway, it now has 195,600 miles on it so i figured i would change my diff fluid just becuause it was freshly rebuilt not long ago. To my suprise, there was a lot of metal shavings stuck all over the magnet, much more than a film. The fluid was not black or burnt smelling, but more like foggy looking. It dont appear to be getting too hot or anything but it seems like that amount of wear metal is too much. I have a 10k mile warranty, so i just want to see if this is normal or not. This truck is never in fwd and just gets used carting kids around. Thanks
99 suburban front diff rebuild, fluid very nasty?
- Thread starter jstutz
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There should be some metal on the magnet from break in but not much. First call the rebuilder and let him know what you found. I would then run it in 4wd for 10-15 mile intervals 4 or 5 times and then drain fill before your warranty expires. If you get more metal you have an issue.
Yea, i was expecting a little film or something due to the new bearings but this seemed excessive. Then again i have never had a diff rebuilt. Ill do the fwd four or five times and see what happens. If it was from just initial break in, would there be more metallic flakes on it agian? How long does it take for them to completly break in?
JHZR2
Staff member
metal on there is likely from breaking in. Unless the diff is noisy or sloppy, I doubt there is an issue.
The foggyness is moisture. While some of the front drivetrain may move, unless youre in 4WD, there is no load going through that diff. As a result, the heat generated in there is very low. This causes the fluid from heating up, and therefore, you get moisture. You dont see it on the rear as it is always under load with use...
The foggyness is moisture. While some of the front drivetrain may move, unless youre in 4WD, there is no load going through that diff. As a result, the heat generated in there is very low. This causes the fluid from heating up, and therefore, you get moisture. You dont see it on the rear as it is always under load with use...
Originally Posted By: jstutz
If it was from just initial break in, would there be more metallic flakes on it agian? How long does it take for them to completly break in?
90% of diff break in occurs in 500 miles. But running a GM 4wd on dry pavement that far is not recommended. (according to GM) That is why I would cycle the system on and off for short distances. If you didn't change the gears they are laready broken in. So you should have very little if any metal. If your lubricant comes out black or has metal in it then I would suspect an issue since you already flushed it out once. Note: If you run the truck in "auto4wd" and do not have all of your tires at equal factory size, treadwear and air pressure it can cycle the system on and off continually.
If it was from just initial break in, would there be more metallic flakes on it agian? How long does it take for them to completly break in?
90% of diff break in occurs in 500 miles. But running a GM 4wd on dry pavement that far is not recommended. (according to GM) That is why I would cycle the system on and off for short distances. If you didn't change the gears they are laready broken in. So you should have very little if any metal. If your lubricant comes out black or has metal in it then I would suspect an issue since you already flushed it out once. Note: If you run the truck in "auto4wd" and do not have all of your tires at equal factory size, treadwear and air pressure it can cycle the system on and off continually.
Okay, thanks fellas. I will keep a very close eye on it, maybe ill find a field or something that i can exercize the 4wd a little and check the fluid. I was very suprised being that 4wd or auto 4wd has never been used. I have read many bad things about the auto system and refuse to use it as i have already spend 1k on getting the transfer case rebuilt. Being that the gears were not replaced, that is why i was so suprised to see that much metal, but i would think if something was wrong the oil would be black from heat and it was not.
Update and some questions. I have been trying to find out what has been groaning in my suburban so after taking the kids to the park today i jacked up the front drivers side and was messing witht he wheel. I spun the wheel as fast as i could and could hear a very pronounced clacking of gears in the front diff. As i slid under the truck, i noticed that the diff was hot. If you stuck the back of your hand on it, you could barely hold it there. should it get that hot in 2wd on a twenty mile trip?
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Could someone give me at least a generic measure of how hot it should get in 2wd. Barely warm, warm, mildly hot, cant touch. Im borderline cant touch with back of hand after 20 to 30 miles of hwy driving. Maybe if someone has a truck that has the auto function could you feel the front diff after a trip and report the temp. Thanks guys.
I once felt the front diff on my truck after a highway run. (In 2wd, but the front gears still spin) It was sort of warm, barely above ambient temp. I could definitely hold my hand on it as long as I wanted. Even the rear diff wasn't much hotter, and that one was actually under load the whole time. It too was easily touchable.
Yes it was.
on my cherokee xj i have hit them with thermal gun and my front is around 130 f
Well here goes with the update. Initially i took it back to the shop where i got the front diff rebuilt to begin with. Guy found the rear drive shaft had a bad ujoint so for 100 bucks he replaced both on the rear driveshaft. Well that was not the problem so i took it back to him. He called me two days later and said he has an electronic listening device of some sort that you can drive the truck, and listen to specific parts of the truck. He said the noise sounds like it is indeed in the front diff. He took the diff out and opened it up and said everything looks good. I dont think he took the pinion bearing and stuff out though. Anyway we decided to change the left front wheelbearing just incase it was bad. Well no dice. Truck still roars going down highway at 65 to 70 mph. It dont really do it going slow. He is going out of town this week and cant get back to my truck until monday. This is going on about 3 weeks now without my suburban which we use to carry our kids around in. It is no fault of his own, he is really trying to do the best he can and i certainly dont know how to help. Does anyone have any other ideas. Just some data.
2wd or 4wd dont matter
front driveshaft on or off, dont matter
front diff rebuilt 8k miles ago
truck was good for a few thousand miles after rebuild and getting worse
The noise is kinda like a bad wheelbearing noise, but more vibration and loose gear sounding.
If anyone knows alot about these and would like to contact me please feel free to email me on here or call my cell 336-404-6452 and ask for jason. All help and advice will be apriciated a lot. Me and mechanic are sick of this problem.
2wd or 4wd dont matter
front driveshaft on or off, dont matter
front diff rebuilt 8k miles ago
truck was good for a few thousand miles after rebuild and getting worse
The noise is kinda like a bad wheelbearing noise, but more vibration and loose gear sounding.
If anyone knows alot about these and would like to contact me please feel free to email me on here or call my cell 336-404-6452 and ask for jason. All help and advice will be apriciated a lot. Me and mechanic are sick of this problem.
I wish I could help. I had my 03 Yukons front diff rebuilt when I bought it used under warranty. It was making a noise that does sound like you described that went away with the rebuild. Will you please let us know what it turns out to be? Good luck. I will ask a mechanic I know what he thinks.
Have you checked the tcase?
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