After finding a lot of helpful information here in the past this is my first post. I tried searching the forums and couldn't find anything that seemed to fit my problem so I thought I'd give this a try.

I have a '02 extended cab, 2WD with a v-6 and 86k miles. About 6 months ago I started to notice a noise from what seems like the rear of the truck. It's hard to describe but a hum is pretty close. It only happens at about 43mph and 1200 RPM. It doesn't happen at any other speed or RPM combination, only this one, and If I let off the gas or accelerate it goes away. I thought maybe it was just me but I know it's there because I can make it happen anytime.

Now about two weeks ago I've started to notice a vibration coming from the dashboard that seems to correspond to the first problem but I'm not sure. The new vibration is more of a harmonic as it will change in frequency and does seem to happen at the same RPM range, regardless of speed. I've made sure there's nothing in the glove box or a loose cup holder. I even made an attempt to tighten some of the accessible screws and bolts on the dash but still there.

Not sure If I have one problem that's getting worse or two separate ones and I'm not sure where to start. I'd like to see if there's anything I can do myself before having to take it to a mechanic. Any help would be greatly appreciated.

 

If I had a hum coming from the back of the truck that developed into a vibration that is bad enough the rattle the dash, I'd park it and start looking at u-joints and the drive shaft. U-joints are easy to check and the drive shaft sometimes throw the weights that keep them balanced, believe me I've had it happen.

 

Since you are 2wd... I would say, but not 100% certain sitting here... that you do not have a limited slip rear. Look on your Driver door label and take note of the axle code and look it up

I have a whining noise in my rear also, but it is constant and I am sure I will have to do bearings very soon. If you have a limited slip rear, and it only vibrates/shutters at slow starts/slower turns.... a gear oil n friction modifier change may solve that one

When you say it goes away when you get on/off the pedal... AND a vibration near the front of your truck... change your U-Joints ASAP... before the driveshaft comes through the floor (I had this happen when I was younger and dam near broke my leg... ain't pretty)

Do you feel the vibration from the floor with your idle foot?

 

The hum and vibration both sound like the driveline to me. Out of balance driveshaft will cause harmonics because it is hallow and the vibration is either a out of balance drive shaft or u-joint on it's way out. If you hear a whinning type sound it is worn gears in the rear end. If you have a 4r70w tranny becareful. I hoola hooped my driveline and snapped the tail housing off the tranny.

 

Thanks for the responses.

Blackferret-I'll take a look at the u-joints and see if it looks like any of the weights may have come off the driveshaft. To clarify the dash isn't actually terribly, it's more like there's something loose right in the middle of the dash. The other thing it reminds me of is the type of sound you may get if the cupholders aren't fully closed or the ashtray isn't fully seated.

Red02Fx4- again I'll check the u-joints, the hum is only at the speed/RPM combination noted, nothing on starts or turns. No actual vibration is felt, just heard.

01 gt f150 - how do I check which tranny I have?

 

Which motor you have and how many bolts and shape of the tranny pan. The 4r70w and 4r75w have an almost square pan with 14 bolts and the 4r100 is rectangular with a notch out of one corner and 20 bolts.

 

There should be a tranny code on the Driver Door plate with a code for the transmission. On mine, it is on the bottom section of the sticker, and the code (mine is "U") would be under the TR part..... this will help:

https://www.f150online.com/forums/ar...e-sticker.html