Question: How to isolate driveline bearing whine? (1 Viewer)

[Schruiser]

HZJ76 w/ r151f transmission
I'm getting some very loud whining noise when I get up to and over 80 km/h. Sounds like a bearing going out. It is only under acceleration/deceleration (i.e. goes away if I disengage the clutch), and also disappears if I remove the rear driveshaft and go in front-wheel-drive mode.
The rear differential and hubs have been rebuilt in the last year, but I wouldn't rule anything out due to the dubious nature of parts and mechanics in my part of the world. The noise has been around for a while, but has recently started increasing to annoying levels.
So my question is: Does the fact that this noise goes away when the rear driveshaft is removed indicate that it is for sure coming from the rear axle? Or could it be something in the transfer case? Any thoughts on how to isolate the noise?

 

[Rigster]

HZJ76 w/ r151f transmission
I'm getting some very loud whining noise when I get up to and over 80 km/h. Sounds like a bearing going out. It is only under acceleration/deceleration (i.e. goes away if I disengage the clutch), and also disappears if I remove the rear driveshaft and go in front-wheel-drive mode.
The rear differential and hubs have been rebuilt in the last year, but I wouldn't rule anything out due to the dubious nature of parts and mechanics in my part of the world. The noise has been around for a while, but has recently started increasing to annoying levels.
So my question is: Does the fact that this noise goes away when the rear driveshaft is removed indicate that it is for sure coming from the rear axle? Or could it be something in the transfer case? Any thoughts on how to isolate the noise?

Is it just noise? Or do you get vibration as well? While the rear drive shaft is out, check the u-joints as well.

If the shop you had the previous work done is reputable, they should not mind double checking the pinion and wheel bearings they say they replaced.

As far as isolating the sound, you may have to get the cruiser in the air and allow the wheels to spin while you carefully listen for said noise.

 

[sodafeld1]

yes I would check ujoints and driveshaft, any vibrations?

 

[AirheadNut]

If it is just noise and not vibration, and given it goes away in front wheel drive, then my first suspect would be the rear output shaft bearing in the transfer case.

 

[sodafeld1]

If it is just noise and not vibration, and given it goes away in front wheel drive, then my first suspect would be the rear output shaft bearing in the transfer case.

yes indeed if no vibrations

 

[Squash]

Try cleaning out the rear slip yoke since you mentioned that the noise is gone if the rear ds is out.
I remove the zerk and spray brake cleaner on penetrative oil into the zerk hole using the little spray tube.
Drive around like this, bumps help.
If the works, return the zerk and only 3 pumps.
To many people over grease this spot which causes the ds to become a straight steel rod rather than a device which allows for the body to move up and down without without putting stress on the rear pumpkin.
Note: To much grease if the grease comes back out of the little ball of your zerk, or if you can see the yoke lengthening and you cannot bounce the body and watch the slip yoke move in and out.

 

[sodafeld1]

Try cleaning out the rear slip yoke since you mentioned that the noise is gone if the rear ds is out.
I remove the zerk and spray brake cleaner on penetrative oil into the zerk hole using the little spray tube.
Drive around like this, bumps help.
If the works, return the zerk and only 3 pumps.
To many people over grease this spot which causes the ds to become a straight steel rod rather than a device which allows for the body to move up and down without without putting stress on the rear pumpkin.
Note: To much grease if the grease comes back out of the little ball of your zerk, or if you can see the yoke lengthening and you cannot bounce the body and watch the slip yoke move in and out.

yes that is often how the rear transfer bearing gets damaged.

 

[Squash]

Rear pinion as well.
Body and yokes need to dance together rather than a tight fight.