I was wondering if any of you guys could help me out here. It seems that when I drive at a constant 45-50 mph, my truck sort of sounds like a helicopter. It sounds like it is coming from the rear tires, from the passenger site from what I can tell. And it doesn't do it other than mainly those speeds.

What it sounds like is a loud thump, thump, thump....real loud and fast. Now the truck doesn't vibrate or pull or feel any different. Could the wheel be out of balance, or maybe something else that has to do with the wheels?

 

Is it possible you locked the tire up when stopping? It would be pretty rare but you may have a flat spot. That would cause a thumping sound. Have you looked at the tires to see if there is anything in them like rocks in between the threads. I have that happen to me since I live down a dirt road, they usually fling out when I start driving.

 

I have the same thing, only in the front and between 20-30mph most noticeable. Mine didn't start until I had the truck in for the tranny flush and fuel filter. They gave me a complimentary tire rotation, which is the only thing I can think must have caused it. I was thinking they knocked a tire weight off or something??

 

Have you inspected each tire closely visually and perhaps by feel? Sounds like a possible case of cupped tires. The original General Grabbers on my '01 Screw began cupping on the inside tread by around 15k to 20k miles. The first thing I noticed was the rythmic thumping sound. I could not feel any vibrations. I had it aligned and increased the frequency of tire rotations, but I think it is still cupping the tires. The sound annoys me to no end, but other than the sound, there are no bad side effects that I can tell. I have 66k miles on those same original tires, with a few thousand left in them. I guess I can't justify replacing them just due to the noise. I will replace them when they wear to the safety bands.

SM

 

Hey had the same problem around 36-38K on my tires. Changed out my left front to the spare, and it went away. So I took it in, found the the tire had uneven wear, and the truck was out of alignment. After talking to the Mech. he recommended that you align cars right after buying them because the factory specfications are not very tight. So I figure I was driving for all those miles out of alignment and even though I rotated the tires every 5-6K, it produced the uneven wear.

Cheers

 

Flat spots can also be caused by running a tire out of balance without know it. On these trucks, it's not hard to do when the tire is on the rear, and it becomes much more noticable when the tire is moved to the front.