Hey guy's,

Just curious, I have a fairly noticeable whine when in 4 hi when off throttle. If I get back in to the throttle it virtually goes away, could it be the chain in the T/C? Its a 99 with 150K+. 4x4 works just fine. Thanks for the info. Brad.

 

Doubtful.

Sounds more like the front pinion bearing in the rear end.

With parking brake on, wheels chocked, and tranny in neutral, see if the pinion is loose by grabbing the driveshaft right in front of the rear-end and push/pull it and see if there is any slack. Also, if you can, disconnect the driveshaft from the rear and try rotating the pinion back and forth. If it's really stiff, the bearing is shot. Is the rear seal at the pinion leaking any oil?

Also, pull the fill plug and see if the magnet has any metal on it.

The transfer case, when NOT in 4x4 is basically a big hanger bearing and shouldn't make any different noise when on or off the throttle.

Really, sounds more like the front pinion bearing.

Check it out quick.

 

I'm not a mechanic but my 99 F250SD did the same thing. First, it was the transfer case motor ($800CA), then it was the right auto hub, and now again the transfer case motor (replaced under warranty since less than 12months from original replacement). I am starting not to like the ESOF and wished that I'd ordered the manual.

 

Just realized this was about when IN 4x4.

My '01, with the stock fluid in the rear-end, had a light whine when cruising at highway speeds in 4x4. Running on the backside of the ring in the rear, apparently..

Changed the fluid, first to Royal Purple, helped a lot, but Mobil 1 made it go completely away.

Still, sounds more like the small pinion bearing in either the front or the rear if it's a loud as you make it seem.

 

Hello Krewat: I understand, Mobil 1 for the rear differential. For the front, are you referring to Mobil 1 in the front differential and/or the transfer case? I thought I read somewhere just standard ATF in the transfer case - anything that I can use to make these things last longer would be great because it's getting too expensive to maintain this '99 although I love the truck otherwise. Thanks for your input in advance.

 

ATF in the transfer case, 75w90 in the front end. I used synth in both.

Where is the whine coming from, the rear of the truck?

And it doesn't do it AT ALL if you're not in 4x4?