at 1250 to 1500rpm my truck has a weird vibration or hum. it only happens when the truck is in overdrive[5th gear,automatic], and it only happens between those rpms going up long grades or on flat ground. the truck is not searching for gears. the second i let off the gas the vibration or hum stops, it is really faint, but i notice it. could it be the exhaust or transmission? the truck is an 05' crew cab, long bed,4x4, with a v-10. the problem occurs when i had the stock tires and with my aftermarket tires, so that can't be the problem. the dealership of course can't find anything, and think i am nuts. any ideas on what i am feeling would be greatly appreciated before i take it back to them.......there is also a shudder at take off if you step on it.

 

I think you are hearing the cooling fan on the engine...it comes on to cool the intercooler and engine and transmission.

 

the truck is a v-10. at any other rpm the engine is really smooth. under those circumstances there is a little vibration or hum.

 

possilby clogged cats... had something that sounds similar to that happen on my Lightning. Only did it at certain rpm's and that was it... otherwise I would have never noticed it.

 

any other suggestions?

 

my neighbors 350 screw dually (powerstroke) does the same thing, I didnt no until he rode with me in my 150 screw and he said i had the same hum. It was faint enough I hadnt actually been bothered by it, just wrote it off to differential noise.
We both think it is in the rearend.

 

Ah, simple...its the torque converter locking in under power on the top side of the gear. Or at least that is my opinion.

I feel the same thing under a load and it seems to dampen pending the grade and throttle gain.

One difference, I only feel this when using a tune for econ or power in that power range.

 

I had the same thing, but mine was at take off up to that RPM, My problem was drive shaft and universal,

Had the drive shaft balanced and no more hum and vibration.

This was after 6 univeral joints in 92000km's.

The dealership will tell you it doesn't need it done.

It cost me 700 Canadian to have from the transmission back to the rear including the hanger.

On a S Crew f350 dually long box

And yes for those who have read some of my other threads I had problems with universal Joints that Ford wouldn't come good for as well.

Stevlin

 

is there a fix for the torque converter, or is this something i live with?

 

Does it make the noise only when the A/C is on?

 

no, it does it when the air is on or off.

 

Concur. I have seen this with bad u-joints too. Only did it under load and within an RPM range.