I have a 2500 HD 4x4 with 160,000 miles, between 65 and 70 mph there is a roaring sound coming from the truck. I can not determine where it is coming from. I can coast at 65-70 mph with no roaring but under power it will roar. Above 70-72 mph it stops roaring and sounds normal. I have checked the dope in the rear end and it is fine. Any suggestions?

If it is a manual transmission, sounds like the front clutch plate.

Harmonic balancer.

sounds like your fuel pump isn't priming you should get the fuel pressure tested if its under fifty thats seems to be your problem

they have a extnded warranty on the speedometer cluster 7 years or 70,000 miles

3 suggestions for you, you may need to check the tire pressure, get a tire alligment done, or you have a bad wheel bearing, usally a bad wheel bearing make's a loud roaring sound going down the road. I hope I have helped you.

I just had the same issue with a 1999 2500HD and the vibration got worse above 50 mph. Problem was resolved with a new driveshaft. Old one (aluminum) was badly out of true and the problem didn't really occur until I had the U joints changed - then bent driveshaft vibration was noticeable. New driveshaft resolved issue.

need to check wheel bearings

Replace transmission.

I have the same thing. It started last summer when I had about 20,000 miles. I just took it into the dealer. They say it is the antenna and that they removed it and tested drove it and the noise went away. Mine starts around 35 mph. I don't know if they are pulling my leg and there is a bigger problem that the financially strapped GM won't fix. I also have a bad CV joint and unless it goes out within the next 500 miles, GM won't replace it.

Yes. Check the Buick Enclave and GMC Acadia boards. Lots of cam shaft problems. Same engine as the Outlook.