99 RWD Singing noise at cruise

[MingoJake]

Just bought a 99 XLT V-8 RWD truck today.

The purchase was about 7 hours from home, so I had a good opportunity to get aquainted with the Explorer on the drive home.

I noticed a singing noise of varying intensity coming from the drive train area.
The noise is constant when the accellerator depressed as in cruise . The noise goes away when coasting, or foot off gas pedal. The O/D and shifting were all normal.

Doesn't appear to be coming from front of truck, more like transmission, rear end, u-joints or axles.

Explorer has 115,000 miles.

Any suggestions will be appreciated.

Jim

 

[my pos mounty]

Sounds like the rear end may have to be rebuilt eventually. The noise you hear is a bearing dying in the rear differential.
Did you get a warranty with the truck?

 

[MingoJake]

No warranty.

Any cost estimates ?

 

[my pos mounty]

That would depend on your plan of attack.
Doing the work yourself? (couple hundred bucks in parts)
Paying a garage to rebuild it? (about $1000 would be my wild-stab-in-the-dark estimate)
Going to play the lottery and get a junkyard rear and swap it in yourself? (100-750 for the rear axle assembly depending on where in Texas you go, plus maybe $100-200 in parts, again depending on what you want to do to it before installing it)
or pay a garage to do that? (cost would be close to rebuilding the one you have in the truck now and not worth the risk)

 

[MingoJake]

Thanks for the good info.

I don't have a plan of attack, have to do some more investigating.

What a great forum, got a reply within 2-3 minutes of posting!

 

[my pos mounty]

Don't be too afraid of driving it. It won't blow up on you for quite some time (as long as theres diff fluid in it, might want to check that). Mine made a horrendous noise like that for close to a year before I just couldn't take the noise anymore and the radio wouldn't go up loud enough to drown it out.
Diff fluid would be 75/140 synthetic, fill to the plug.

 

[MingoJake]

Thanks

I will check the fluid level tomorrow.

 

[pwrshft99]

Not sure what gearing you have, I think 3.73 are commin and 4.10s are with towing packages.

If you have 4.10s or higher ratio, they tend to whine at cruising speeds. I had an 8.8 built for my Mustang with 4.10s and it howled pretty good between 2500-3000 rpm. I took it back thinking the backlash wasn't set up properly but everything checked out ok.

 

[fraxinusalba]

Check the pinion bearings. The outer one tends to get pitted on these things. Had to replace in my 97 and 99. Fairly cheap, easy fix and no more whine. Replace the gear oil too and visually check the gears for damage or pitting while the plate is off.

 

[MingoJake]

Thanks

I am sure that replacing pinion bearing instructions are to be found in this forum.

 

[fraxinusalba]

If you have basic mechanical abilities, its pretty easy for the outer one. Mark drive shaft and differential yoke for alignment on reassembly. Remove rear drive shaft from differential yoke being sure not to allow needle bearing caps to fall off U-joint (recommend taping them on). Remove yoke retaining nut. Gear puller to remove yoke. Pry out pinion seal. Little wiggle of the pinion shaft and bearing should loosen enough to remove with fingers.