Los

Need some help trying to figure out a problem with my truck.
First, my truck is a 2001 Tacoma Doublecab 4x4.

When ever i put it in 4wd and get above 15 miles per hour, it starts to make this humming noise thats coming from the drivetrain, it keeps getting louder and louder until finally at 30 miles per hour its so loud that I feel like somethign is going to break. The noise goes away for the most part when I let off the gas. I've been keeping it out of 4 till I figure out this problem.
Obviously its coming from the front, since it only happens when I put it in 4wd. But Im trying to figure out if its a ujoint or my differential bearing...
Its not a clunking noise, and I just lubed the zerks to see if that would do anything, but no dice.

Any thoughts? I really hope its not the diff bearing...as I think thats going to be pricey. Any one know how much it would cost to have the diff bearing replaced? Just want to get myself prepared incase its not the ujoints...

Thanks.

ciscojay

I had a horrid vibration/humming noise for about 5000 miles and even had a shop put those electronic ear things on the vehicle and drove it around to isolate where it was coming from. They thought it was the front diff..same symptoms, speed, hearing it mostly on throttle. I swore that it was coming from my front diff as well, but it actually ended up being my left rear wheel bearing. Got progressively worse until it finally blew apart and grenaded my left drum brake. I figured that it was coincidental and would just get it fixed, but I was suprised to discover that the humming/vibrations went away all together. It's insane to think the vibrations from that wheel bearing were traveling through the whole drivetrain. Anyway, just my experience...something to consider.

Also, you're in the Springs...if you find that it's a bad front diff and need one, I have an A03A front that I bought used. Not sure if that will fit your taco.

Los

Thanks for the response... if I do need a front diff, i'll let you know.
I just cant imagine it being a wheel bearing as it only happens in 4wd... even if it was a front wheel bearing, you should hear it all the time, not just in 4wd. I just really think its something related to the front half of the 4wd system.

ciscojay

oh doh! I skimmed over the post and missed the 4wd part hehe...yeah let me know if you need that diff. If you need someone to look at it might wanna check out Toyota Tech off of Iowa st...they're awesome. Tell em Jay sent you their way.

Los

do you know what gearing it has? How can i find out if it would fit? Also what gearing does it have, My truck came w/ 4.10 gears I believe.
And how much would you want incase I needed it?

ciscojay

A03A has 4.10 gears...you can find out what front you have for sure by looking at the manufacturer sticker on the inside of your driver doorwell. You can also verify by calling a Toyota dealer and giving them your VIN, they can look it up for you.

PM me if you need...I'd get it checked out first though.

Los

Sent you a pm