Odd "whine" under acceleration only

[lander]

Hello all!

I have a '98 Sport 4x4 4.0 OHV (X VIN) 4sp manual w/OD.

The question I have is that while accelerating, or at least, while on the gas only, I have a sort of "whine" that comes out from, best I can determine, the rear end area...i.e. it sounds like it's coming from behind me in the cabin. No...it's not the exhaust.

It's not rotational as best I can determine because I can be cruising along flat and level and if I let off the gas, the "whine" goes away...press the gas slightly, not even really accelerating, and the "whine" comes back.

Thoughts? And no...it's not the wife or anything, it does it even when I'm driving by myself.

TIA

 

[BrooklynBay]

Welcome to this forum! There is a TSB on the rear end whine in the Technician Forum section, but it's for a different year: http://www.explorerforum.com/forums/showthread.php?t=157872

 

[lander]

Ack! I searched, but missed that one.

Crap...bearings...gears...that would suck. I'll try changing to the 75w140 synthetic first and see if that sorts it out.

Thanks!!!

 

[gijoecam]

My money is on bad pinion bearings. Classic symptoms. The longer you wait to repair it, the more expensive the repair's gonna get. If you do it now while it's just a whine, you may get away with just bearings and a crush sleeve. If you wait, you may be looking at those plus a ring and pinion plus carrier bearings, plus axle bearings and seals...

Don't wait. It's not going to go away on its own.

 

[lander]

So I'm guessing it's a load based noise? Which makes the bearings going bad make sense.

Is this a DIY project? I'm not afraid of tearing down the diff myself, but if it requires any special tools, etc., I'm screwed.

 

[gijoecam]

Those that have rebuilt diffs before can chime in on this one. For me, when the time becomes necessary, I'll rent/beg/borrow/buy the tools I need to do the job. I'm quite sure I'm capable... I work on gearboxes MUCH bigger than a rear end, or an Explorer for that matter. But without the proper tools, it makes the job tougher. Search a bit, and someone's probably got a how-to here with pics.

 

[lander]

Thanks! I'll be sure to do a better search than I did the first time!

One thought that may just be a long shot here. The vent tube for the rear axle was broken off right at the axle. It was one of the first things I noticed after I bought the truck a few weeks back. I just temporarily fixed it with some electrical tape.

Would it be conceivable that I've lost so much oil from the rear diff through that vent that it's causing the noise and that just by replacing the oil I'd be ok? This thing has 175k on it and isn't a daily driver...just something I use around town to haul things.

I think I'll start by getting some rear gear oil and see how much oil comes out when I go to replace it.

I really do appreciate your help!