1998 Olds Bravada 4.3L AWD SmartTrac

This may be nothing. I do not drive this vehicle very often since its my spouses. Today when I moved it I thought the transmission was whinning in drive and reverse, not in neutral or Park.

I let it warm up and check fluid it was OK..just a little dark but smelled good. Was changed about 15,000 miles ago with screen. I test drove and it was shifting good into all gears but definitely whinning.

Is this whinning sound normal? It almost reminded me of my 1982 GMC with the hubs locked in but the transfer case in 2wd.

It also has a check engine light which I have not checked for code yet. I assume its the O2 sensor since they need to be changed. But is there any codes pertaining to the transmission?

Any thoughts will be greatly appreciated! Thanks.

 

There are a ton of codes and your CEL could be on for any one of them.

What makes you think that the O2 sensors need to be changed? If you do change them, only change the upstream sensors (the ones before the "Y" in the y-pipe) and keep the old ones around for spares when/if the down stream sensor (after the cat) fails. You do not replace an emissions monitoring sensor until it pops a code.

About the problem, have you made sure that the transfer case is full? It requires GM Autotrak2 fluid for proper operation of the clutch pack.

Does the noise change with ground speed or RPM?

Do you have to be going a certain speed to detect the noise?

 

I had a code about a year ago that went away and it was a downstream O2 sensor.

I will check the transfer case soon. I know it only has Dextron 3 Transmission fluid in it because I changed it about a year ago...that's what the Haynes Manual said to put in it...Should I get some GM Autotrak2??

As the RPM's increase the whine also increases to a higher pitch. Any speed you can hear it. When coasting- No sound -regardless of speed. No sound in Park.

Thanks for your quick response...It is appreciated

 

YIKES! Hopefully you did not ruin the clutches. The Haynes manual leaves a lot to be desired. Your owners manual shows what the proper fluids are. Both the NV136 (AWD) and NV236 (Auto4wd) transfer cases require Autotrak2 fluid.

 

Yep I was just doing a little research and I feel like a DumbDonkee. I will hopefully keep from doing any more damage by changing the fluid. Thanks for the info.

 

Now I am really confused. I just went and got my owners manual....It says to use DextronIII. I then went and looked at the Haynes Manual and it said either DextronIII or Autotrac2. Now I am thinking that tomorrow when I get in from work...checking out everything...both differentials & changinging to autotrac.

 

The NV233 (standard transfer case for the S-series vehicles) is the only transfer case to use DexronIII. The NV236 and NV136 require Autotrak2.