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GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
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Experience:  GM Grand Master Technician 2007. 14 years experience.
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1999 chevy tahoe 4x4 front diferential problems

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1999 chevy tahoe 4x4 front diferential problems
Hello, I'm Cam. Please include all the details about your issue so I can accurately advise you. I cannot see your vehicle so please be detailed.

Is there any play in the axle shaft?

WEar or marks on the shaft?

I doubt the bearing is bad, rather I think the seal surface is dirty or compromised.

You can use a very fine emery cloth to clean the surface up.

Also check the vent to make sure it is free flowing.
Customer: replied 4 years ago.
the axle has spindle nut at outter end by wheel and has a 5 or 6 bolt plate at the inner side near the differential. when you remove the axle. (which i am doing because it is bad) there is the plate that it bolts to going into the differentil. if i remove that plate there is a seal in the diferential just like a axle seal on a front wheel drive tranny. i have replaced that seal once just a few months ago. but now its leaking as bad as it was if not worse than the frst time i changed
Yes that is exactly what I was expecting based on your original question, but I need to know if the inner surface of the axle flange or stub axle as it is called, has marks or dirt built up.

Second, is the seal correct? I have seen enough when the wrong seal is given out.

third, pressure build up due to heat, and a vent that is plugged will cause the seal which is a weak point to fail and leak again. Is that happening?
Customer: replied 4 years ago.

to be honest, those are things i'll have to find out, i havent really pulled it apart again. it was an autozone seal so its likely that it may be a bad seal. since i am going to replace axle anyway, i am going to replace seal again (dealer only this time) but before i ordered parts. i was curious if there was a bearing in the houseing that the axle stub goes into. if there was i was going to order it too. im sure i can check the stub and wire wheel or emery cloth it clean


The seal has a small bearing behind it, and it would be visable with the seal off.

I would inspect the stub shaft closely before replacing it, Why replace it if there are no issues.
Customer: replied 4 years ago.
for the extra 40 bucks its worth it for peace of mind and as long as i have it apart its only a few more minutes of work. i just was thinking if the bearing is bad it may be causing the stub to wobble off center enough to cause it to leak. im just one of those guys that is anal about being over thorough. but its been a few months since i had it apart and i could remember if there was a bearing in there. also. i almost forgot. there is a high pitched hum (like an elephant shreaking) coming from the front end. starts at about 35 miles an hour and gets louder the faster i go. but i cant get it to do it once i have the truck up on the lift. hub assemblys are both new. i know the axle is bad but ive never heard this noise before. at least not from an axle
Does the noise change when you turn side to side?
Customer: replied 4 years ago.

no. just when i speed up or slow down


If you remove the front driveshaft from the differential to the transfer case, does the noise go away?
Customer: replied 4 years ago.
havent tried that yet but i was thinkin the same thing, probably do that tomorrow when i change the axle. if it doesnt go awaay when i change the axle then i'll pull front drive shaft and see what happens. i'll let ya know tomoorow. thanks for everything. you definatley pointed me in the right doirection. this is where the leak isgraphic
Great minds think alike?

Yes that is a very commonly point on most front differentials.
I could not begin to count the number I have replaced.
Customer: replied 4 years ago.

so as common as it is. how often is the bearing bad. or i should say, whats the most common reason for it going bad?


The most common reason for the seal leaking is dirt underneath the seal, he seal surface, or just a bad quality seal. Now with your humming noise along with it, I do suspect there's something else going on such as the differential side bearing or something like that that may be playing a role in this leak.
Customer: replied 4 years ago.
well. im gonna change bearing seal and axle. . if i still hear noise, i'll remove front drive shaft.. i'll let ya kknow what i find. thanks a bunch
My pleasure, be sure you bookmark this page so you can reply back easily for follow-up information.
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Customer: replied 4 years ago.
you got it