Front differential issue

[john cris]

I noticed a fair amount of grime, and oil caked along lower front suspension components on the passenger front and decided to pressure wash the area to see where the leak was coming from. In the past I’ve had to replace the seal for the half shaft where it enters the differential. After cleaning everything I checked the oil level in the differential, found it low and added some 75/90 gear oil I had on hand. I did not overfill or get to the point of oil spilling from the fill plug. I knew it was low but had no issues so I didn’t want to overfill. Since I did that the differential now makes a humming noise and has a slight variation. Guess I should have left the damn thing alone, geez.
This is quite noticeable from about 30 mph and is really worrying on the freeway. So much so I won’t take it on the freeway.
Should I drain the differential? Would that even be worth doing? Why would adding oil seemingly create such an issue? The book says 80/90 oil, but seriously how could 75/90 be so bad? Sorry guys, just very frustrating. This is my only vehicle currently and it’s got 230k miles on it.
Suggestions please

 

[FordFlintrock]

Strange yes. The only thing different is your 75-90 is prolly synthetic where the 80-90 is conventional I believe for front axles.

 

[john cris]

Strange yes. The only thing different is your 75-90 is prolly synthetic where the 80-90 is conventional I believe for front axles.

I appreciate the response.
Your probably correct about the new oil being synthetic, I’ll have to check. I did top this off a few years ago when I replaced that axle seal and that was probably synthetic also but I can’t remember exactly.

 

[mountaineer2004]

If it were me, I'd drain out all the old and refill with the specified 80/90 conventional. If you still have a problem, at 230k, something in the differential's going bad, and the timing is purely coincidental.

 

[john cris]

Yeah, I took it to a local shop this morning. The owner of the shop test drove it and the news was not good. On Tuesday next week he wants to put it on a lift and listen to different areas to confirm. He said it’s possible it could just be output bearings for the half shafts which would be an easier and less expensive repair. At least that would give me some time to find something else. I doubt that’s how this will go but the owner said he would put it on the rack at no charge, so worth a shot. I agree this is probably coincidental. This isn’t a total surprise. The front differential is definitely not the only problem it has. Rear differential is suspect as are timing chains. And to top it off he said the transmission is slipping in 3rd. None of that is a surprise. I’ve been looking to replace the explorer for awhile so now I’ve got to get more serious
Thanks guys

 

[mountaineer2004]

Yeah, I took it to a local shop this morning. The owner of the shop test drove it and the news was not good. On Tuesday next week he wants to put it on a lift and listen to different areas to confirm. He said it’s possible it could just be output bearings for the half shafts which would be an easier and less expensive repair. At least that would give me some time to find something else. I doubt that’s how this will go but the owner said he would put it on the rack at no charge, so worth a shot. I agree this is probably coincidental. This isn’t a total surprise. The front differential is definitely not the only problem it has. Rear differential is suspect as are timing chains. And to top it off he said the transmission is slipping in 3rd. None of that is a surprise. I’ve been looking to replace the explorer for awhile so now I’ve got to get more serious
Thanks guys

Yes, it's time to retire your old vehicle. Although I'm highly resistant to it, sometimes change is the better choice. Simply drive it till it stops.