4th gear, 40mph, loud rattle type noise.

I have a 06 PreRunner SR5 access cab, 4cyl, manual 5 speed, 87k...

Between about 40-45 MPH in 4th gear I have a loud, what sounds like a loose heat shield vibrating. It only happens under a load. Driving on level ground, at a steady speed I'm fine. If I accelerate the noise starts, the harder I accelerate the louder it gets. If I start going up a incline and add any throttle to maintain speed, the noise starts. This is very pronounced, like at its loudest point I think people in houses I'm driving by could hear it.

A similar noise has developed at the same speeds while de-accelerating. Its not as pronounced, but its a rougher more mechanical type rattle/grinding noise.

The same vibrating noise has also started to become noticeable in 3rd gear around the 2,000 RPM range(I don't recall the speed). Again this is accelerating and de-accelerating.

A little history on the truck;

This truck was a one owner, it had every oil change from the day it was driven off the lot done at the same dealer according to the carfax. Besides maintenance, there was nothing else listed.

I purchased the truck from carmax(mistake I will never make again). The truck had this noise when I purchased it. I was crossing my fingers it was just a loose heat shield. The more I drove it, the more I started to realize that it was something in the transmission. I took it back to carmax, they looked it over and concluded it was in the tranny. They sent it to a hole in the wall transmission shop. They tore it apart and said a couple bearings were a little burnt, so they replaced them. They also said it looked like it had a new clutch(I'm suspicious of this new clutch as its not on the carfax).
When I picked the truck up, it still had the exact same noise. I immediately returned it to carmax. They sent it to a dealer who again confirmed the noise was in the transmission. Carmax then sent it back to the hole in the wall tranny shop. This time they put a used tranny in it. Either that or they painted the original one black and put it back in.
Again when I picked the truck back up, it still had the exact same noise. At this point I told carmax they were never touching my truck again.

So I'm going to make a guess that this "used" tranny is not going to have the exact same problem. So this leaves something on the front of the tranny, like the throw out bearing, or something with the clutch.

Another little thing to note, when coasting in first gear with clutch in, I hear a light rubbing noise, when I slide it out of gear the noise goes away. I don't know if this is normal, or if it might be tied to the other noise.

I apologize if there is already a thread open on this.

Any ideas?

 

Check your Cat heat shields. i bought a 2005 Tacoma and it had this problem brought it to the dealership and they thought it was the skid plate. 1 week later i heard it again so i crawled under the truck and saw the bolts on the shield were in bad shape 2 were loose and couldn't be tightened so i took them off no noise. Good Luck they don't come off easy!

 

Thanks for the input, any is appreciated. The heat shield has been checked and double checked. Its not the culprit.

This is confirmed by being under a load at 40mph while the noise is very loud, I can start to depress the clutch and noise gets quieter. The farther I press the clutch the quieter it gets until clutch starts slipping and the noise is gone completely.