91 Ranger vibration and hum

[commradd]

Just bought a 1991 Ext cab 2wd Ranger with the 4.0L and the automatic. The harder i accelerate, the more vibration there is. This is mostly noticeable at low speed. Around 30 it smooths out and around 45 the vibration starts to come back. From 45 on, you can hear a humm that comes and goes about every 2 seconds, then goes away for 2 seconds, then comes back for 2 seconds and so on. A vibration is also felt but the vibration is almost always there regardless of the humming. The 2 second interval (roughly) tells me that it's probably not the tires or wheels since it isn't consistent with rotation. I'm thinking u-joint, torque convert, or carrier bearing bushing. I'm hoping that it's not the transmission. Does anyone have any ideas? I'm going to start troubleshooting this evening, so i'm hoping for some ideas.

Thanks.

 

[Rangersrule91]

I had the same problem with my 91 ext cab and i replaced the u-joints and it was gone, but it wasnt a cheap fix. Also check the Harmonic Balancer (i think this year has one).

 

[commradd]

I just took it for a spin again, it's about every second that the hum comes and goes at freeway speeds. I'll look at the u-joints first then. Anyone know how much play in the carrier bearing is to much?