Chevy Suburban Rear Diff Hum

[JDR15467]

I have a 99 Suburban that has always made a high pitch hum between 45 and 50 MPH. My mechanic told me that this was common with this model of GM product, but wanted to see if others have experienced this. If so, has anyone been able to dampen the hum using a different type of diff oil?

Thanks
John

 

[Kestas]

It is possible to have gears with systematic hum if they are made less than perfect. This is typically true if they are made with old machinery.

 

[DoubleDee]

Does it have the G80 locking differential? This has been known to be noisy and may need the modifier. Amsoil Severe Gear has the additive in it, but if it would still make the noise, you can also put in their additive. Check in the glovebox on the option tag for G80.

 

[punisher]

Look for TSBs/Service Bulletins for this concern. I have fixed gear whines/hums with everything from new ring&pinions, different durometer spring bushings and even tieing up a parking brake cable transmitting noise from the axle housing.

 

[JDR15467]

I have the original sticker, and all it shows is a 3.73 Locking Differential. I did find G80 listed along with many other numbers in the glovebox on a sticker for Parts Identification.
Thanks for the advice.

 

[JDR15467]

I also wanted to mention that about a year ago it was really growling in the back end. My mechinic fixed the growling with a new rear axle bearing, wheel seal, and axle. That took care of the growling sound, but the hum remained. It has always had the hum, which he said these where notorious for.

 

[mechtech2]

No matter what,I'd get the best fluid that you can afford.
Hypoid gears have to b set up jut right to minimize noise.
When you change the lube, note the pattern on the teeth, and compare it to pictures and charts for hypoid teeth mating.

 

[JDR15467]

What would be a good recommended oil that I can get at the local stores?
Thanks

 

[wtd]

It might be the pinion and carrier bearings. These are known to go out in the 10 bolt rear ends. I had to have the ones replaced in the rear of my 98 ECSB Z71 at about 75,000 miles

 

[DoubleDee]

I would go with a synthetic at your parts store. Mobil 1, Valvoline, or if available and you will spend the money, Royal Purple. If they don't have the modifier in them, go to a GM dealership and ask for the G80 additive. It is a little bottle.