Mos

Hey guys,
I am a pretty new owner of a 99 Suburban that needs some work done here and there.

After I did some driving with it, I noticed a whining sound inside the car. I can't figure out where it comes from excatly, it just feels like it is everywhere.
It occurs between 40-50mph and is the loudest when holding speed at around 50mph. As I accelerate hard it gets quiter.
If I don't step on the gas pedal at all and let the car roll, it also gets quieter and disappears....
At speeds over 60mph it is gone or not noticeable anymore.

There is no difference between driving in D-overdrive or in regular drive (3). I also tried only second gear and the same thing happens.
ATF level is full.
Oil in the rear diff is also new and full.

I am really going crazy, because i can't figure out where this is coming from.

LarryE

My 99 suburban does that with the AC on. It might be the extra load put on the belt tensioner or belt idler or maybe the compressor but the AC is working fine so far.It is time for me to change the tensioner, idler,and belt anyway.Turn the AC off and see if the noise stops.Good luck.

Rednucleus

Get up to the whining speed, put in neutral, see if it changes. Can also turn off and see if it goes away - that would mean not engine associated noise.

Mos

I'm very sure the noise has nothing to do with the engine. I haven't tried to put it in neutral yet, but as soon I go off the gas pedal it goes away. There is also no difference betwen AC on or off.
I've noticed a little play in the u-joints. Got two new ones and will put them in tomorrow. Allthough I got only little hope that this will fix it.

Next step would be to check the rear wheel bearings. They seem to have a slight up and down play on both sides. I'm gonna take brake drums off and have a closer look.
After some research I found out that bad pinion bearings in the diff can couse a whining noise when under load. But I feel absolutely no play at the pinion yoke or anything suspicious on the diff.

Maybe somebody has a good idea to check for a bad pinion bearing without taking it apart.
I'll keep you all updated, maybe some of you are also struggling with the same problem.

Josiebelle

Last year my 2003 z71 had the whining/high pitch roar. It was definitely the wheel bearings. My mechanic changed it out, the following week...the other side starting singing to me. From now on, if it's affordable, I will change both sides at the same time.

David Lu

My 1999 K2500 has this exact issue. Did you ever figure out what was causing it for you?

mountainmanjoe

@David Lu This thread hasn't been touched in a while. Please make a new thread in the correct section with all your vehicle details (miles/engine/transmission), details about the symptoms, and all the troubleshooting you tried. Thanks.