Strange sound from drive train

I have just purchase a 2005 tacoma, and am realizing I may have a issue unannounced to me... The truck drives very good although I noticed that there is a wind up humming noise while accelerating that remains constant until I slow to a stop. Sounds to me that the front wheels are spinning the front differential at all times although I am not in 4wd... I have aftermarket wheels, if that means anything... So, are my suspicions accurate? Are my front hubs constantly locked? I am certain Its not a Hub assembly or worn bearing issue, as I have already looked into this.. I have tried putting the truck in 4wd going a few blocks. stopping. turned off 4wd. then driving again and the noise stayed exactly the same... pleeeease help
Thanks
-Amos

 

Yes, front hubs are constantly locked and the front axle shafts are constantly turning.

How many miles on the truck?

Does the humming stop when braking?
Is it matched to RPM's ....or wheel spin?
How old/worn are the tires? Try rotating the tires and see if the 'hum' goes away or changes frequency.

 

The Noise does not match with Rpms only with speed. There is 73xxx miles on the truck. The humming does not stop when braking but I can hear it wind down as I come to a stop. There is no difference in sound when driven in hi4 or hi2, however I do feel the difference (the power) in hi4. I notice that when I switch out of hi4 there sounds to be no dissconnection -- then the noise does not change at all. Do know what this means exactly? Is this a major repair? Thank you for the response I'm dying to know more.

 

Troubleshooting is never easy, never quick, and almost impossible for us to pinpoint - because we are not in your truck.

How old are your tires? Rotate your tires and see if the 'noise' changes in loudness or direction. Believe it or not, but old & worn tires can cause noises on the roadway.

Troubleshooting involves a process of elimination.

 

Thanks for the reply. The problem is the my truck has had an alignment balance and tire rotation recently... So because of this I'm ruling out the possibility of just tire noise. Let me ask you this. With your tacoma, when you switch into four wheel drive do you hear an obvious sound from the front end, when the front wheels are behind powered that sounds like a small airplane engine? (Wind up and wind down when accel/deccelling sound) Or when you shift out of 4wd do you hear a difference in your engine sound?? Thanks again!

 

It could still be tire noise, especially if the tires are old. Just last week, I was out test driving vehicles with my mother-in-law. The one vehicle had a pretty loud 'whallop' sound that sounded like a wheel bearing was going bad. Vehicle drove true and felt good. It was still under factory drive train warranty, so even if it had a bad bearing....we weren't worried. As part of the purchase agreement, we had the dealer install new tires. The sound was gone completely. Just something to think about....

Putting the truck into 4WD, you will often hear a 'click' and YES - it can whine a bit. And yes, the engine can 'sound' different. And yes, it will feel different also - you are driving with 4 wheels and not 2. This just depends on the severity / loudness of that noise. I can't tell you what the difference is.

When was the last time the oil was changed in your differentials, transfer case, and/or transmission (manual)?? When was the last time the driveshafts were lubricated?

Do you know the history of the vehicle? Has it been in 4WD often? Have you tried getting it into 4LO??
Do you have a auto or manual?