Rear axle drone

[Ericalan350]

I have a 1994 4.0 2WD (manuel trans) that recently between 55-65 mph I start hearing a drone sound as if there is a semi truck getting close to me. It gets a little bit louder up to 75-80 mph. It doesn't get better or worse as I decelerate or accelerate. I am in the process of changing the fluid in the diff between yesterday and today (it was time to change the fluid anyway). The internal diff looks fine. No excessive wear that I can see, no shavings or broken teeth. The truck has 275K on it. Has anyone ever had this issue that they can shed some light on where to look or a check list?

Also, does anyone know of a better way to refill the diff? I have a 5/16" clear tube and it is frustrating to say the least.

Thanks in advance for any helpful advice!

 

[Dirtman]

You can pick up a gear oil pump at pretty much any auto parts store for a few bucks, they just screw on the bottle of gear oil.

As for the noise, at 275k id be checking u-joints, pinion bearing, and wheel bearings.

 

[Ericalan350]

You can pick up a gear oil pump at pretty much any auto parts store for a few bucks, they just screw on the bottle of gear oil.

As for the noise, at 275k id be checking u-joints, pinion bearing, and wheel bearings.

The issue with refilling is the attempting to get the bottle close enough to the vertical fill hole on the pumpkin. With the gas tank in the way it makes for a tough angle to directly refill.

Regarding the noise, I replaced the U joints and the wheel bearings less than a year ago. I will put the pinion bearing on the check list though!

Thanks Dirtman,

 

[Dirtman]

Do you have a limited slip rear? they can get noisy when they get worn as well.

 

[Ericalan350]

Do you have a limited slip rear? they can get noisy when they get worn as well.

It is not a limited slip.

 

[Uncle Gump]

2 piece driveshaft? Carrier bearing could be suspect.

Something to think about.... might help you narrow it down. Driveshaft and wheel bearing noises tend to come in different frequencies. Depending on gear ratio... the driveshaft operates 3 or 4 times wheel speed. They just sound or feel different.

 

[Ericalan350]

2 piece driveshaft? Carrier bearing could be suspect.

Something to think about.... might help you narrow it down. Driveshaft and wheel bearing noises tend to come in different frequencies. Depending on gear ratio... the driveshaft operates 3 or 4 times wheel speed. They just sound or feel different.

It is a 8.8 with a 3.08 gear. I will add carrier bearing along with the pinion bearing to the check list.

Thanks man

 

[AllanD]

When I had a front pinion fail in my rear diff it sounded like someone had left a running turbo-shaft (helicopter engine) in my bed, it "whistles" at a steady cruise.

 

[Will]

Good to see you around, AllanD!