Differential Noise

I've searched old threads for something similar with absolutely zero luck.

Truck is a 2001 SC PreRunner 2.7 with 49k miles. When I'm accelerating, all is quiet. When I'm off the throttle, all is quiet.

There is a sweet spot where my differential whines. I'm assuming when there is no positive or negative force on the gears they're just all loose in there causing them to make noise.

This led me to believe there might be play in the diff. I got under there and could turn it about a quarter of an inch.

Any suggestions on what I need to do about this?

 

Have you ever replaced the front needle bearing? Common weak spot on the trucks dating back to 1995.

 

No. Can you explain what that is?

 

It's not 4wd so not front needle bearings. Could be a rear axle bearing on it's way out.

 

It's made this noise for the past year. Hasn't gotten any worse, but it's annoying as hell.

It doesn't sound like a bearing going bad. It's more of a gear sound than a howling bearing noise. Could a bad bearing could cause the gears to be out of alignment and thus cause the play in the gear set?

 

Most differentials will make that noise if you slightly load it on coasting, I can make 2015's do it. It's when it gets to the point where the noise happens all the on and off the throttle it becomes an issue.

The play you tested is backlash, which can cause the noise. But the real concern with a noise like that is the pinions movement laterally. It's normal for a pinion to move slightly up and down when you push up against it (unloaded in the air) but if the play is excessive the pinion bearing itself is the cause of the noise. It's hard to gauge this and experience goes a long way.

Either way a pinion bearing/back lash crush sleeve replacement is a pain in the ass. I'd wait for it to get worse personally.

My 2 cents

 

Thanks for that.

I'm not quite following what you mean when you say it's normal for it to move up and down. When I turn the prop shaft by hand back and forth I can actually hear the gears hitting each other. Is that normal?

 

Mine does that too and so does another members on here that I hang out with.

 

Some backlash is necessary. A 1/4" of movement is not excessive. But you might wanna keep an eye on it to see if it increases.

How long has it been since the 3rd was serviced? How many miles on that gear oil. If you are unsure, do the oil change. The diff drain plug is magnetic and will collect any debris (metal shavings) floating around in the oil. Chunks would indicate a problem. Some metal paste/cream stuck on the drain plug is normal.

 

I had the diff oil replaced about 3k miles ago. I'm beginning to think this is one of those "truck noises" that I just need to get used to.

 

Could be coming from the carrier bearing. See if you can move it around with your hands.

 

I don't have a carrier (center support) bearing.