humming noise r/f

i have replaced it and it went away. if it was a gear hub the noise wouls haooen when you turn and when you drive around 50 to 75 mph

Hate to pull out an old thread, but my dealer spent several visits looking into this and determined it to be pinion gears and diagnosed as normal. To correct my situation, they disconnected the vacuum switch mentioned early on in these threads. By doing so, it locked the front wheels so they spin together as they would in 4HI. This is why the noise disappeared when you found the vacuum switch disconnected. The problem is common, but worse in some Blazers than others. I was told it was within tolerance spec.

Sounds fishy to me.
Check the fluid level in the front diff. Also it just might be the front diff outer axle shaft bearing going bad( dry lack of lube) and when its put into 4 wheel drive there is lube going out to the bearing.
Just an idea to think about.

Yo Fireplug, I need to change my right side axle shaft bearing, it hums a tune sometimes.

Never done one before and the book absolutely sucks, it assumes that you have the front diff completely out.

In looking it over, it appears that I can unbolt the inner CVJ, support the front diff, unbolt the 5 bolts and remove the actuator, the axle support and I should be able to remove the axle tube.

Does this sound right?

Hate to pull out an old thread, but my dealer spent several visits looking into this and determined it to be pinion gears and diagnosed as normal. To correct my situation, they disconnected the vacuum switch mentioned early on in these threads. By doing so, it locked the front wheels so they spin together as they would in 4HI. This is why the noise disappeared when you found the vacuum switch disconnected. The problem is common, but worse in some Blazers than others. I was told it was within tolerance spec.

Something is wrong here, vacuum is used to LOCK the front axle, therefore disconnecting the vacuum should have made it unlock or freewheel.

From your description, if the vacuum was removed and the noise went away, sounds as if the front axle was engaged.

I have a k1500 book out in my tool box let me go check it. They are all the same s and k trucks
To remove the front diff is a piece of cake.
Most times we would take out all the bolts but 1 and roll the diff down and keep it in the truck and help hold it there with a tall stand. While you are at it replace both seals.
And there is a special sealer to use on the shaft (spelling sucks) anarobic sealer , its red in color

Both seals? Is there an inner and outer on the axle tube? And what is this special sealer?

The one bolt your talking about, is that the one on the diff housing itself? Also, are you disconnecting both inner CVJ's to allow it to swing down and say, rest it on a transmission jack?

Something is wrong here, vacuum is used to LOCK the front axle, therefore disconnecting the vacuum should have made it unlock or freewheel.

From your description, if the vacuum was removed and the noise went away, sounds as if the front axle was engaged.

It might be my misunderstanding of how the switch works. I definitely get the sound when it "freewheels". The dealer did something to the vacuum switch to allow my front wheels to remain locked and that eliminates the vibration from 40-60km/h. Disconnected vacuum might have been the easiest way for them to explain it to me without going into detail.

The one bolt your talking about, is that the one on the diff housing itself? Also, are you disconnecting both inner CVJ's to allow it to swing down and say, rest it on a transmission jack?


YEP

Both seals? Is there an inner and outer on the axle tube? And what is this special sealer?

BOTH SIDES 1 driver side and 1 pass side
while its just hanging there do both sides.
The reason we would just hang the diff was being flat rate you did not want to bother anyone else and have them loose time and money + we found that you can save a lot of time not having to take it all the way out.
The sealer will only be needed if you remove the axle tube from the diff. Its a specal type of sealer that needs no air to cure. Its not to big of a deal if you dont have it on the tube housing

i Just

I Just Got A 99 Blazer And Mine Is Making The Grinding Noise In The Front Some Where And Goes Away In 4 Wheel Drive Then When Switched Back To 3 Wheel Drive Noise Starts Back Up A Few Mins Later Any Help

Mine STILL does it.
I ignored it for a while, but now it is worse and getting loud. Pretty sure it's the bearing. 2WD, 4WD no difference. Gets slightly quieter when turning left. Is there a how-to out there on changing the hub and bearing assembly?

Mine STILL does it.
I ignored it for a while, but now it is worse and getting loud. Pretty sure it's the bearing. 2WD, 4WD no difference. Gets slightly quieter when turning left. Is there a how-to out there on changing the hub and bearing assembly?

I found this guy's page helpful. http://members.aol.com/s10man4x4/fhub.htm

Looks good...should be helpful. Thank you.

FINALLY, I did mine last night, after all this time that I put it off.
It was EASY...came right off. No more humming noise. Did the front brakes too.
Yes, I know how old this thread is.

What about if there is a humming noise in all gears but neutral and park? Reguardless if moving or not. noise changes pitch when motor is revved up. It used to go away with higher engine rpm's, but is constant now. Also does it in 4x4. Tranny fluid was just changed along with filter and new pan gasket, and no it was not back flushed, and there were no little sparklies in it. it was brownish from age. I was thinking it was maybe the transfer case vacuum module like you guys described. Where exactly is it, and how do i diagnose without just replacing it? My next best guess is the torque converter, but with the fluid without any metel shavings in it, i really hope thats not the issue.

by the way, Its a 95 GMC Jimmy SLE 4.3L V6 4L60E. thanks

I would check trans line pressure, as you could have a torque converter or transmission front pump going bad.

im completely transmission illiterate. Untill next year, how do i do that?