Help needed

[MOAK]

At 92,000 miles my NP 241 has developed a very low pitched howl when engaged in 4H. It begins at around 25 mph and gets progressively louder and higher pitched as speed increases. I just now have noticed it because its the first time in several years that I've had it up more than 30 mph when engaged in 4H.... Is this simply the chain howling and nothing to worry about till I hear it rattle in 4L? BTW, it only howls under torque.. Thanks for any input ..

 

[Gaucho919]

Sounds like it might be a front output shaft bearing, I'd get under there and try to feel for any play in the front yoke.

 

[MOAK]

I'll check that next weekend, would it be immediately noticeable? ie slop ?

 

[MOAK]

Wouldn't it be leaking though?

 

[Gaucho919]

Prob wouldn't leak much since that seal is above the fluid level, only the chain takes oil up there. But even the slightest play in the bearing would cause that howl in 4HI, even a U-joint or a front axle yoke bearing.

 

[MOAK]

Hmmm

The front driveshaft was completely rebuilt a short time ago, and meticulously maintained. It must be the bearing.

 

[bob91yj]

Don't count the driveshaft out. I had a grinding noise on acceleration in my YJ several years ago... I overhauled my Tcase, swapped transmissions out, and did a 1" body lift/motor mount lift to correct driveshaft angles, only to discover that it was the CV in my relatively new rear driveshaft the whole time.