I've recently rebuilt my engine and after 9 years of the truck sitting in the back yard, it is driving again. Before I started driving it, I replaced the transmission fluid with ATF+4. When I first started driving it again, it shifted smoothly and locked up normally but I noticed that that there was a roaring/vibration that occurred every time I went over 47 mph and persisted as long as I was at that speed. The roaring/vibration also occurred occasionally (and for only a couple seconds) at other speeds but only when the transmission was in overdrive and I was beginning to accelerate gently. So I didn't go faster than 45 mph until after I took it to the transmission shop. I have no reason to suspect the engine -it runs smooth as a sewing machine all the way up the rpm range.

The transmission shop owner tested the transmission by various methods and said it shifted fine and the torque converter was good and was locking up properly. He replaced both solenoids and tightened up a lever (I believe the one resting on the accumulator piston) which he showed me had at least 1/4" play before tightening. After that, the roaring/vibration now occurs regularly at 72+ mph and increases in severity from 72 to 80 mph. I have not taken it over 80 as the roaring/vibration is fairly severe at this speed. Interestingly, the roaring/vibration still occurs occasionally (maybe once every two or three times I drive it) at lower speeds, but only when the transmission is in overdrive and I begin to accelerate gently -during these instances, it seems that the transmission is stuck in overdrive and the only way to get it to go into a lower gear for acceleration is to briefly take my foot off the gas and then accelerate more aggressively, which results in the transmission shifting into a lower gear.

It has been suggested that I have a bearing going out somewhere which is vibrating at its harmonic frequency when a certain speed is reached. However, due to the occasional but infrequent appearance of the roaring/vibration at various lower speeds, and the speed at which it was constant changed from 47 to 72 after the transmission was tinkered with, I am inclined to think this is transmission or transfer case related. Any ideas?

 

Do you feel the vibration thru the steering, or the seat?

Can you localize where the noise is coming from?? (not just a bad fan clutch, is it?)

 

I feel the vibration through the seat and steering but it's more noticeable through the steering. I cannot localize the noise, but I replaced my clutch fan with a dual e-fan setup from TCP, so that's not it.

 

No. I guess not.

Rotate your tires. See if anything changes.