Fixed 4wd, now howling noise

[4x4ever]

I have a 90 XJ and last night I fixed the 4wd by shimming over the fork which engages 4wd with some washers, now when I'm driving on the highway and get up to speed there is a deafening low howling noise comming from the front. But there are no vibrations and it didn't make this noise when the 4wd didn't work and the front driveshaft wasn't constatly turning. The only thing I can think is something in the transfer cause but I'm not sure. Any ideas?

[mtsz52784]

Are you sure it is not engaged? I know if I engage at higher speeds there seems to be a howling noise.

[4x4ever]

Are you sure it is not engaged? I know if I engage at higher speeds there seems to be a howling noise.

I don't think it's engaged, dummy light is off and there's not bucking when I turn the wheel full lock

[MoparManiac]

check ur front driveshaft u-joints? lifted at all?

[4x4ever]

check ur front driveshaft u-joints? lifted at all?

Haven't checked the U-joints, how do I tell if they're bad or not? and no not lifted

[MoparManiac]

put the vehicle in neutral, block the tires, and check for slop in the u-joints by rotating the pinion yoke or front transfer case yoke with one hand and the driveshaft itself with the other. If they don't move together then one or more of the caps probably lost its needle bearings (aka they rusted away).

[4x4ever]

put the vehicle in neutral, block the tires, and check for slop in the u-joints by rotating the pinion yoke or front transfer case yoke with one hand and the driveshaft itself with the other. If they don't move together then one or more of the caps probably lost its needle bearings (aka they rusted away).

I'll try that and replace if necessary but I can't imagine those are making all that noise on the highway, is there anything else it could possibly be?

[4x4ever]

bump for some more help

[ready to mud]

check your front diff fluid. if it is bad or low it could cause the howling. i would also guess it could be your u joints